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294 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Linus Torvalds
|
7a3fad30fd |
Random number generator updates for Linux 6.11-rc1.
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||
Jason A. Donenfeld
|
9651fcedf7 |
mm: add MAP_DROPPABLE for designating always lazily freeable mappings
The vDSO getrandom() implementation works with a buffer allocated with a
new system call that has certain requirements:
- It shouldn't be written to core dumps.
* Easy: VM_DONTDUMP.
- It should be zeroed on fork.
* Easy: VM_WIPEONFORK.
- It shouldn't be written to swap.
* Uh-oh: mlock is rlimited.
* Uh-oh: mlock isn't inherited by forks.
- It shouldn't reserve actual memory, but it also shouldn't crash when
page faulting in memory if none is available
* Uh-oh: VM_NORESERVE means segfaults.
It turns out that the vDSO getrandom() function has three really nice
characteristics that we can exploit to solve this problem:
1) Due to being wiped during fork(), the vDSO code is already robust to
having the contents of the pages it reads zeroed out midway through
the function's execution.
2) In the absolute worst case of whatever contingency we're coding for,
we have the option to fallback to the getrandom() syscall, and
everything is fine.
3) The buffers the function uses are only ever useful for a maximum of
60 seconds -- a sort of cache, rather than a long term allocation.
These characteristics mean that we can introduce VM_DROPPABLE, which
has the following semantics:
a) It never is written out to swap.
b) Under memory pressure, mm can just drop the pages (so that they're
zero when read back again).
c) It is inherited by fork.
d) It doesn't count against the mlock budget, since nothing is locked.
e) If there's not enough memory to service a page fault, it's not fatal,
and no signal is sent.
This way, allocations used by vDSO getrandom() can use:
VM_DROPPABLE | VM_DONTDUMP | VM_WIPEONFORK | VM_NORESERVE
And there will be no problem with OOMing, crashing on overcommitment,
using memory when not in use, not wiping on fork(), coredumps, or
writing out to swap.
In order to let vDSO getrandom() use this, expose these via mmap(2) as
MAP_DROPPABLE.
Note that this involves removing the MADV_FREE special case from
sort_folio(), which according to Yu Zhao is unnecessary and will simply
result in an extra call to shrink_folio_list() in the worst case. The
chunk removed reenables the swapbacked flag, which we don't want for
VM_DROPPABLE, and we can't conditionalize it here because there isn't a
vma reference available.
Finally, the provided self test ensures that this is working as desired.
Cc: linux-mm@kvack.org
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
|
||
Kefeng Wang
|
28bdacbcb3 |
mm: move memory_failure_queue() into copy_mc_[user]_highpage()
Patch series "mm: migrate: support poison recover from migrate folio", v5.
The folio migration is widely used in kernel, memory compaction, memory
hotplug, soft offline page, numa balance, memory demote/promotion, etc,
but once access a poisoned source folio when migrating, the kernel will
panic.
There is a mechanism in the kernel to recover from uncorrectable memory
errors, ARCH_HAS_COPY_MC(eg, Machine Check Safe Memory Copy on x86), which
is already used in NVDIMM or core-mm paths(eg, CoW, khugepaged, coredump,
ksm copy), see copy_mc_to_{user,kernel}, copy_mc_{user_}highpage callers.
This series of patches provide the recovery mechanism from folio copy for
the widely used folio migration. Please note, because folio migration is
no guarantee of success, so we could chose to make folio migration
tolerant of memory failures, adding folio_mc_copy() which is a #MC
versions of folio_copy(), once accessing a poisoned source folio, we could
return error and make the folio migration fail, and this could avoid the
similar panic shown below.
CPU: 1 PID: 88343 Comm: test_softofflin Kdump: loaded Not tainted 6.6.0
pc : copy_page+0x10/0xc0
lr : copy_highpage+0x38/0x50
...
Call trace:
copy_page+0x10/0xc0
folio_copy+0x78/0x90
migrate_folio_extra+0x54/0xa0
move_to_new_folio+0xd8/0x1f0
migrate_folio_move+0xb8/0x300
migrate_pages_batch+0x528/0x788
migrate_pages_sync+0x8c/0x258
migrate_pages+0x440/0x528
soft_offline_in_use_page+0x2ec/0x3c0
soft_offline_page+0x238/0x310
soft_offline_page_store+0x6c/0xc0
dev_attr_store+0x20/0x40
sysfs_kf_write+0x4c/0x68
kernfs_fop_write_iter+0x130/0x1c8
new_sync_write+0xa4/0x138
vfs_write+0x238/0x2d8
ksys_write+0x74/0x110
This patch (of 5):
There is a memory_failure_queue() call after copy_mc_[user]_highpage(),
see callers, eg, CoW/KSM page copy, it is used to mark the source page as
h/w poisoned and unmap it from other tasks, and the upcomming poison
recover from migrate folio will do the similar thing, so let's move the
memory_failure_queue() into the copy_mc_[user]_highpage() instead of
adding it into each user, this should also enhance the handling of
poisoned page in khugepaged.
Link: https://lkml.kernel.org/r/20240626085328.608006-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20240626085328.608006-2-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
||
Chengming Zhou
|
a0b856b617 |
mm/ksm: optimize the chain()/chain_prune() interfaces
Now the implementation of stable_node_dup() causes chain()/chain_prune() interfaces and usages are overcomplicated. Why? stable_node_dup() only find and return a candidate stable_node for sharing, so the users have to recheck using stable_node_dup_any() if any non-candidate stable_node exist. And try to ksm_get_folio() from it again. Actually, stable_node_dup() can just return a best stable_node as it can, then the users can check if it's a candidate for sharing or not. The code is simplified too and fewer corner cases: such as stable_node and stable_node_dup can't be NULL if returned tree_folio is not NULL. Link: https://lkml.kernel.org/r/20240621-b4-ksm-scan-optimize-v2-3-1c328aa9e30b@linux.dev Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Stefan Roesch <shr@devkernel.io> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Chengming Zhou
|
d58a361b03 |
mm/ksm: don't waste time searching stable tree for fast changing page
The code flow in cmp_and_merge_page() is suboptimal for handling the ksm
page and non-ksm page at the same time. For example:
- ksm page
1. Mostly just return if this ksm page is not migrated and this rmap_item
has been on the rmap hlist. Or we have to fix this rmap_item mapping.
2. But we absolutely don't need to checksum for this ksm page, since it
can't change.
- non-ksm page
1. First don't need to waste time searching stable tree if fast changing.
2. Should try to merge with zero page before search the stable tree.
3. Then search stable tree to find mergeable ksm page.
This patch optimizes the code flow so the handling differences between ksm
page and non-ksm page become clearer and more efficient too.
Link: https://lkml.kernel.org/r/20240621-b4-ksm-scan-optimize-v2-2-1c328aa9e30b@linux.dev
Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Stefan Roesch <shr@devkernel.io>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
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Chengming Zhou
|
ac90c56bbd |
mm/ksm: refactor out try_to_merge_with_zero_page()
Patch series "mm/ksm: cmp_and_merge_page() optimizations and cleanup", v2. This series mainly optimizes cmp_and_merge_page() to have more efficient separate code flow for ksm page and non-ksm anon page. - ksm page: don't need to calculate the checksum obviously. - anon page: don't need to search stable tree if changing fast and try to merge with zero page before searching ksm page on stable tree. Please see the patch-2 for details. Patch-3 is cleanup also a little optimization for the chain()/chain_prune interfaces, which made the stable_tree_search()/stable_tree_insert() over complex. I have done simple testing using "hackbench -g 1 -l 300000" (maybe I need to use a better workload) on my machine, have seen a little CPU usage decrease of ksmd and some improvements of cmp_and_merge_page() latency: We can see the latency of cmp_and_merge_page() when handling non-ksm anon pages has been improved. This patch (of 3): In preparation for later changes, refactor out a new function called try_to_merge_with_zero_page(), which tries to merge with zero page. Link: https://lkml.kernel.org/r/20240621-b4-ksm-scan-optimize-v2-0-1c328aa9e30b@linux.dev Link: https://lkml.kernel.org/r/20240621-b4-ksm-scan-optimize-v2-1-1c328aa9e30b@linux.dev Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Stefan Roesch <shr@devkernel.io> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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|
Kefeng Wang
|
aa1b94891c |
mm: ksm: drop KSM_KMEM_CACHE()
After commit
|
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|
Chengming Zhou
|
c2dc78b86e |
mm/ksm: fix ksm_zero_pages accounting
We normally ksm_zero_pages++ in ksmd when page is merged with zero page, but ksm_zero_pages-- is done from page tables side, where there is no any accessing protection of ksm_zero_pages. So we can read very exceptional value of ksm_zero_pages in rare cases, such as -1, which is very confusing to users. Fix it by changing to use atomic_long_t, and the same case with the mm->ksm_zero_pages. Link: https://lkml.kernel.org/r/20240528-b4-ksm-counters-v3-2-34bb358fdc13@linux.dev Fixes: |
||
|
Chengming Zhou
|
730cdc2c72 |
mm/ksm: fix ksm_pages_scanned accounting
Patch series "mm/ksm: fix some accounting problems", v3.
We encountered some abnormal ksm_pages_scanned and ksm_zero_pages during
some random tests.
1. ksm_pages_scanned unchanged even ksmd scanning has progress.
2. ksm_zero_pages maybe -1 in some rare cases.
This patch (of 2):
During testing, I found ksm_pages_scanned is unchanged although the
scan_get_next_rmap_item() did return valid rmap_item that is not NULL.
The reason is the scan_get_next_rmap_item() will return NULL after a full
scan, so ksm_do_scan() just return without accounting of the
ksm_pages_scanned.
Fix it by just putting ksm_pages_scanned accounting in that loop, and it
will be accounted more timely if that loop would last for a long time.
Link: https://lkml.kernel.org/r/20240528-b4-ksm-counters-v3-0-34bb358fdc13@linux.dev
Link: https://lkml.kernel.org/r/20240528-b4-ksm-counters-v3-1-34bb358fdc13@linux.dev
Fixes:
|
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|
Chengming Zhou
|
90e8234988 |
mm/ksm: fix possible UAF of stable_node
The commit |
||
|
Linus Torvalds
|
61307b7be4 |
The usual shower of singleton fixes and minor series all over MM,
documented (hopefully adequately) in the respective changelogs. Notable
series include:
- Lucas Stach has provided some page-mapping
cleanup/consolidation/maintainability work in the series "mm/treewide:
Remove pXd_huge() API".
- In the series "Allow migrate on protnone reference with
MPOL_PREFERRED_MANY policy", Donet Tom has optimized mempolicy's
MPOL_PREFERRED_MANY mode, yielding almost doubled performance in one
test.
- In their series "Memory allocation profiling" Kent Overstreet and
Suren Baghdasaryan have contributed a means of determining (via
/proc/allocinfo) whereabouts in the kernel memory is being allocated:
number of calls and amount of memory.
- Matthew Wilcox has provided the series "Various significant MM
patches" which does a number of rather unrelated things, but in largely
similar code sites.
- In his series "mm: page_alloc: freelist migratetype hygiene" Johannes
Weiner has fixed the page allocator's handling of migratetype requests,
with resulting improvements in compaction efficiency.
- In the series "make the hugetlb migration strategy consistent" Baolin
Wang has fixed a hugetlb migration issue, which should improve hugetlb
allocation reliability.
- Liu Shixin has hit an I/O meltdown caused by readahead in a
memory-tight memcg. Addressed in the series "Fix I/O high when memory
almost met memcg limit".
- In the series "mm/filemap: optimize folio adding and splitting" Kairui
Song has optimized pagecache insertion, yielding ~10% performance
improvement in one test.
- Baoquan He has cleaned up and consolidated the early zone
initialization code in the series "mm/mm_init.c: refactor
free_area_init_core()".
- Baoquan has also redone some MM initializatio code in the series
"mm/init: minor clean up and improvement".
- MM helper cleanups from Christoph Hellwig in his series "remove
follow_pfn".
- More cleanups from Matthew Wilcox in the series "Various page->flags
cleanups".
- Vlastimil Babka has contributed maintainability improvements in the
series "memcg_kmem hooks refactoring".
- More folio conversions and cleanups in Matthew Wilcox's series
"Convert huge_zero_page to huge_zero_folio"
"khugepaged folio conversions"
"Remove page_idle and page_young wrappers"
"Use folio APIs in procfs"
"Clean up __folio_put()"
"Some cleanups for memory-failure"
"Remove page_mapping()"
"More folio compat code removal"
- David Hildenbrand chipped in with "fs/proc/task_mmu: convert hugetlb
functions to work on folis".
- Code consolidation and cleanup work related to GUP's handling of
hugetlbs in Peter Xu's series "mm/gup: Unify hugetlb, part 2".
- Rick Edgecombe has developed some fixes to stack guard gaps in the
series "Cover a guard gap corner case".
- Jinjiang Tu has fixed KSM's behaviour after a fork+exec in the series
"mm/ksm: fix ksm exec support for prctl".
- Baolin Wang has implemented NUMA balancing for multi-size THPs. This
is a simple first-cut implementation for now. The series is "support
multi-size THP numa balancing".
- Cleanups to vma handling helper functions from Matthew Wilcox in the
series "Unify vma_address and vma_pgoff_address".
- Some selftests maintenance work from Dev Jain in the series
"selftests/mm: mremap_test: Optimizations and style fixes".
- Improvements to the swapping of multi-size THPs from Ryan Roberts in
the series "Swap-out mTHP without splitting".
- Kefeng Wang has significantly optimized the handling of arm64's
permission page faults in the series
"arch/mm/fault: accelerate pagefault when badaccess"
"mm: remove arch's private VM_FAULT_BADMAP/BADACCESS"
- GUP cleanups from David Hildenbrand in "mm/gup: consistently call it
GUP-fast".
- hugetlb fault code cleanups from Vishal Moola in "Hugetlb fault path to
use struct vm_fault".
- selftests build fixes from John Hubbard in the series "Fix
selftests/mm build without requiring "make headers"".
- Memory tiering fixes/improvements from Ho-Ren (Jack) Chuang in the
series "Improved Memory Tier Creation for CPUless NUMA Nodes". Fixes
the initialization code so that migration between different memory types
works as intended.
- David Hildenbrand has improved follow_pte() and fixed an errant driver
in the series "mm: follow_pte() improvements and acrn follow_pte()
fixes".
- David also did some cleanup work on large folio mapcounts in his
series "mm: mapcount for large folios + page_mapcount() cleanups".
- Folio conversions in KSM in Alex Shi's series "transfer page to folio
in KSM".
- Barry Song has added some sysfs stats for monitoring multi-size THP's
in the series "mm: add per-order mTHP alloc and swpout counters".
- Some zswap cleanups from Yosry Ahmed in the series "zswap same-filled
and limit checking cleanups".
- Matthew Wilcox has been looking at buffer_head code and found the
documentation to be lacking. The series is "Improve buffer head
documentation".
- Multi-size THPs get more work, this time from Lance Yang. His series
"mm/madvise: enhance lazyfreeing with mTHP in madvise_free" optimizes
the freeing of these things.
- Kemeng Shi has added more userspace-visible writeback instrumentation
in the series "Improve visibility of writeback".
- Kemeng Shi then sent some maintenance work on top in the series "Fix
and cleanups to page-writeback".
- Matthew Wilcox reduces mmap_lock traffic in the anon vma code in the
series "Improve anon_vma scalability for anon VMAs". Intel's test bot
reported an improbable 3x improvement in one test.
- SeongJae Park adds some DAMON feature work in the series
"mm/damon: add a DAMOS filter type for page granularity access recheck"
"selftests/damon: add DAMOS quota goal test"
- Also some maintenance work in the series
"mm/damon/paddr: simplify page level access re-check for pageout"
"mm/damon: misc fixes and improvements"
- David Hildenbrand has disabled some known-to-fail selftests ni the
series "selftests: mm: cow: flag vmsplice() hugetlb tests as XFAIL".
- memcg metadata storage optimizations from Shakeel Butt in "memcg:
reduce memory consumption by memcg stats".
- DAX fixes and maintenance work from Vishal Verma in the series
"dax/bus.c: Fixups for dax-bus locking".
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Merge tag 'mm-stable-2024-05-17-19-19' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull mm updates from Andrew Morton:
"The usual shower of singleton fixes and minor series all over MM,
documented (hopefully adequately) in the respective changelogs.
Notable series include:
- Lucas Stach has provided some page-mapping cleanup/consolidation/
maintainability work in the series "mm/treewide: Remove pXd_huge()
API".
- In the series "Allow migrate on protnone reference with
MPOL_PREFERRED_MANY policy", Donet Tom has optimized mempolicy's
MPOL_PREFERRED_MANY mode, yielding almost doubled performance in
one test.
- In their series "Memory allocation profiling" Kent Overstreet and
Suren Baghdasaryan have contributed a means of determining (via
/proc/allocinfo) whereabouts in the kernel memory is being
allocated: number of calls and amount of memory.
- Matthew Wilcox has provided the series "Various significant MM
patches" which does a number of rather unrelated things, but in
largely similar code sites.
- In his series "mm: page_alloc: freelist migratetype hygiene"
Johannes Weiner has fixed the page allocator's handling of
migratetype requests, with resulting improvements in compaction
efficiency.
- In the series "make the hugetlb migration strategy consistent"
Baolin Wang has fixed a hugetlb migration issue, which should
improve hugetlb allocation reliability.
- Liu Shixin has hit an I/O meltdown caused by readahead in a
memory-tight memcg. Addressed in the series "Fix I/O high when
memory almost met memcg limit".
- In the series "mm/filemap: optimize folio adding and splitting"
Kairui Song has optimized pagecache insertion, yielding ~10%
performance improvement in one test.
- Baoquan He has cleaned up and consolidated the early zone
initialization code in the series "mm/mm_init.c: refactor
free_area_init_core()".
- Baoquan has also redone some MM initializatio code in the series
"mm/init: minor clean up and improvement".
- MM helper cleanups from Christoph Hellwig in his series "remove
follow_pfn".
- More cleanups from Matthew Wilcox in the series "Various
page->flags cleanups".
- Vlastimil Babka has contributed maintainability improvements in the
series "memcg_kmem hooks refactoring".
- More folio conversions and cleanups in Matthew Wilcox's series:
"Convert huge_zero_page to huge_zero_folio"
"khugepaged folio conversions"
"Remove page_idle and page_young wrappers"
"Use folio APIs in procfs"
"Clean up __folio_put()"
"Some cleanups for memory-failure"
"Remove page_mapping()"
"More folio compat code removal"
- David Hildenbrand chipped in with "fs/proc/task_mmu: convert
hugetlb functions to work on folis".
- Code consolidation and cleanup work related to GUP's handling of
hugetlbs in Peter Xu's series "mm/gup: Unify hugetlb, part 2".
- Rick Edgecombe has developed some fixes to stack guard gaps in the
series "Cover a guard gap corner case".
- Jinjiang Tu has fixed KSM's behaviour after a fork+exec in the
series "mm/ksm: fix ksm exec support for prctl".
- Baolin Wang has implemented NUMA balancing for multi-size THPs.
This is a simple first-cut implementation for now. The series is
"support multi-size THP numa balancing".
- Cleanups to vma handling helper functions from Matthew Wilcox in
the series "Unify vma_address and vma_pgoff_address".
- Some selftests maintenance work from Dev Jain in the series
"selftests/mm: mremap_test: Optimizations and style fixes".
- Improvements to the swapping of multi-size THPs from Ryan Roberts
in the series "Swap-out mTHP without splitting".
- Kefeng Wang has significantly optimized the handling of arm64's
permission page faults in the series
"arch/mm/fault: accelerate pagefault when badaccess"
"mm: remove arch's private VM_FAULT_BADMAP/BADACCESS"
- GUP cleanups from David Hildenbrand in "mm/gup: consistently call
it GUP-fast".
- hugetlb fault code cleanups from Vishal Moola in "Hugetlb fault
path to use struct vm_fault".
- selftests build fixes from John Hubbard in the series "Fix
selftests/mm build without requiring "make headers"".
- Memory tiering fixes/improvements from Ho-Ren (Jack) Chuang in the
series "Improved Memory Tier Creation for CPUless NUMA Nodes".
Fixes the initialization code so that migration between different
memory types works as intended.
- David Hildenbrand has improved follow_pte() and fixed an errant
driver in the series "mm: follow_pte() improvements and acrn
follow_pte() fixes".
- David also did some cleanup work on large folio mapcounts in his
series "mm: mapcount for large folios + page_mapcount() cleanups".
- Folio conversions in KSM in Alex Shi's series "transfer page to
folio in KSM".
- Barry Song has added some sysfs stats for monitoring multi-size
THP's in the series "mm: add per-order mTHP alloc and swpout
counters".
- Some zswap cleanups from Yosry Ahmed in the series "zswap
same-filled and limit checking cleanups".
- Matthew Wilcox has been looking at buffer_head code and found the
documentation to be lacking. The series is "Improve buffer head
documentation".
- Multi-size THPs get more work, this time from Lance Yang. His
series "mm/madvise: enhance lazyfreeing with mTHP in madvise_free"
optimizes the freeing of these things.
- Kemeng Shi has added more userspace-visible writeback
instrumentation in the series "Improve visibility of writeback".
- Kemeng Shi then sent some maintenance work on top in the series
"Fix and cleanups to page-writeback".
- Matthew Wilcox reduces mmap_lock traffic in the anon vma code in
the series "Improve anon_vma scalability for anon VMAs". Intel's
test bot reported an improbable 3x improvement in one test.
- SeongJae Park adds some DAMON feature work in the series
"mm/damon: add a DAMOS filter type for page granularity access recheck"
"selftests/damon: add DAMOS quota goal test"
- Also some maintenance work in the series
"mm/damon/paddr: simplify page level access re-check for pageout"
"mm/damon: misc fixes and improvements"
- David Hildenbrand has disabled some known-to-fail selftests ni the
series "selftests: mm: cow: flag vmsplice() hugetlb tests as
XFAIL".
- memcg metadata storage optimizations from Shakeel Butt in "memcg:
reduce memory consumption by memcg stats".
- DAX fixes and maintenance work from Vishal Verma in the series
"dax/bus.c: Fixups for dax-bus locking""
* tag 'mm-stable-2024-05-17-19-19' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (426 commits)
memcg, oom: cleanup unused memcg_oom_gfp_mask and memcg_oom_order
selftests/mm: hugetlb_madv_vs_map: avoid test skipping by querying hugepage size at runtime
mm/hugetlb: add missing VM_FAULT_SET_HINDEX in hugetlb_wp
mm/hugetlb: add missing VM_FAULT_SET_HINDEX in hugetlb_fault
selftests: cgroup: add tests to verify the zswap writeback path
mm: memcg: make alloc_mem_cgroup_per_node_info() return bool
mm/damon/core: fix return value from damos_wmark_metric_value
mm: do not update memcg stats for NR_{FILE/SHMEM}_PMDMAPPED
selftests: cgroup: remove redundant enabling of memory controller
Docs/mm/damon/maintainer-profile: allow posting patches based on damon/next tree
Docs/mm/damon/maintainer-profile: change the maintainer's timezone from PST to PT
Docs/mm/damon/design: use a list for supported filters
Docs/admin-guide/mm/damon/usage: fix wrong schemes effective quota update command
Docs/admin-guide/mm/damon/usage: fix wrong example of DAMOS filter matching sysfs file
selftests/damon: classify tests for functionalities and regressions
selftests/damon/_damon_sysfs: use 'is' instead of '==' for 'None'
selftests/damon/_damon_sysfs: find sysfs mount point from /proc/mounts
selftests/damon/_damon_sysfs: check errors from nr_schemes file reads
mm/damon/core: initialize ->esz_bp from damos_quota_init_priv()
selftests/damon: add a test for DAMOS quota goal
...
|
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Matthew Wilcox (Oracle)
|
b650e1d2ae |
mm/memory-failure: pass the folio to collect_procs_ksm()
We've already calculated it, so pass it in instead of recalculating it in collect_procs_ksm(). Link: https://lkml.kernel.org/r/20240412193510.2356957-12-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Jane Chu <jane.chu@oracle.com> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Oscar Salvador <osalvador@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
2aa339120c |
mm/ksm: remove page_mapcount() usage in stable_tree_search()
We want to limit the use of page_mapcount() to the places where it is absolutely necessary. If our folio has a stable node, it is a (small) KSM folio -- see folio_stable_node(). Let's use folio_mapcount() in stable_tree_search() instead, which results in no functional change. The mapcount > 1 check is a bit confusing, because that's usually a check for page sharing. Looks like the reason is that we are guaranteed to not exceed ksm_max_page_sharing for the tree KSM folio when merging with that. Let's update the documentation to make that clearer. Link: https://lkml.kernel.org/r/20240416172533.663418-1-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Alex Shi <alexs@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Alex Shi (tencent)
|
452e862f43 |
mm/ksm: replace set_page_stable_node by folio_set_stable_node
Only single page could be reached where we set stable node after write protect, so use folio converted func to replace page's. And remove the unused func set_page_stable_node(). Link: https://lkml.kernel.org/r/20240411061713.1847574-11-alexs@kernel.org Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
85b67b0104 |
mm/ksm: rename get_ksm_page_flags to ksm_get_folio_flags
As we are removing get_ksm_page_flags(), make the flags match the new function name. Link: https://lkml.kernel.org/r/20240411061713.1847574-10-alexs@kernel.org Signed-off-by: David Hildenbrand <david@redhat.com> Signed-off-by: Alex Shi <alexs@kernel.org> Reviewed-by: Alex Shi <alexs@kernel.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Chris Wright <chrisw@sous-sol.org> Cc: Hugh Dickins <hughd@google.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Alex Shi (tencent)
|
79899cce33 |
mm/ksm: convert chain series funcs and replace get_ksm_page
In ksm stable tree all page are single, let's convert them to use and folios as well as stable_tree_insert/stable_tree_search funcs. And replace get_ksm_page() by ksm_get_folio() since there is no more needs. It could save a few compound_head calls. Link: https://lkml.kernel.org/r/20240411061713.1847574-9-alexs@kernel.org Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Cc: David Hildenbrand <david@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Alex Shi (tencent)
|
40d707f33d |
mm/ksm: use folio in write_protect_page
Compound page is checked and skipped before write_protect_page() called, use folio to save a few compound_head checks. Link: https://lkml.kernel.org/r/20240411061713.1847574-8-alexs@kernel.org Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Alex Shi (tencent)
|
72556a4c06 |
mm/ksm: use ksm_get_folio in scan_get_next_rmap_item
Save a compound_head call. Link: https://lkml.kernel.org/r/20240411061713.1847574-7-alexs@kernel.org Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Alex Shi (tencent)
|
6f528de298 |
mm/ksm: use folio in stable_node_dup
Use ksm_get_folio() and save 2 compound_head calls. Link: https://lkml.kernel.org/r/20240411061713.1847574-6-alexs@kernel.org Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Alex Shi (tencent)
|
9d5cc14093 |
mm/ksm: use folio in remove_stable_node
Pages in stable tree are all single normal page, so uses ksm_get_folio() and folio_set_stable_node(), also saves 3 calls to compound_head(). Link: https://lkml.kernel.org/r/20240411061713.1847574-5-alexs@kernel.org Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Alex Shi (tencent)
|
b8b0ff244d |
mm/ksm: add folio_set_stable_node
Turn set_page_stable_node() into a wrapper folio_set_stable_node, and then use it to replace the former. we will merge them together after all place converted to folio. Link: https://lkml.kernel.org/r/20240411061713.1847574-4-alexs@kernel.org Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Alex Shi (tencent)
|
f39b6e2dc1 |
mm/ksm: use folio in remove_rmap_item_from_tree
To save 2 compound_head calls. Link: https://lkml.kernel.org/r/20240411061713.1847574-3-alexs@kernel.org Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Alex Shi (tencent)
|
b91f94729d |
mm/ksm: add ksm_get_folio
Patch series "transfer page to folio in KSM". This is the first part of page to folio transfer on KSM. Since only single page could be stored in KSM, we could safely transfer stable tree pages to folios. This patchset could reduce ksm.o 57kbytes from 2541776 bytes on latest akpm/mm-stable branch with CONFIG_DEBUG_VM enabled. It pass the KSM testing in LTP and kernel selftest. Thanks for Matthew Wilcox and David Hildenbrand's suggestions and comments! This patch (of 10): The ksm only contains single pages, so we could add a new func ksm_get_folio for get_ksm_page to use folio instead of pages to save a couple of compound_head calls. After all caller replaced, get_ksm_page will be removed. Link: https://lkml.kernel.org/r/20240411061713.1847574-1-alexs@kernel.org Link: https://lkml.kernel.org/r/20240411061713.1847574-2-alexs@kernel.org Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Paolo Bonzini
|
f7842747d1 |
mm: replace set_pte_at_notify() with just set_pte_at()
With the demise of the .change_pte() MMU notifier callback, there is no notification happening in set_pte_at_notify(). It is a synonym of set_pte_at() and can be replaced with it. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Message-ID: <20240405115815.3226315-5-pbonzini@redhat.com> Acked-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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David Hildenbrand
|
e3b4b1374f |
mm: convert page_try_share_anon_rmap() to folio_try_share_anon_rmap_[pte|pmd]()
Let's convert it like we converted all the other rmap functions. Don't introduce folio_try_share_anon_rmap_ptes() for now, as we don't have a user that wants rmap batching in sight. Pretty easy to add later. All users are easy to convert -- only ksm.c doesn't use folios yet but that is left for future work -- so let's just do it in a single shot. While at it, turn the BUG_ON into a WARN_ON_ONCE. Note that page_try_share_anon_rmap() so far didn't care about pte/pmd mappings (no compound parameter). We're changing that so we can perform better sanity checks and make the code actually more readable/consistent. For example, __folio_rmap_sanity_checks() will make sure that a PMD range actually falls completely into the folio. Link: https://lkml.kernel.org/r/20231220224504.646757-39-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Peter Xu <peterx@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yin Fengwei <fengwei.yin@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
18e8612e56 |
mm/ksm: page_remove_rmap() -> folio_remove_rmap_pte()
Let's convert replace_page(). Link: https://lkml.kernel.org/r/20231220224504.646757-28-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Peter Xu <peterx@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yin Fengwei <fengwei.yin@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
977295349e |
mm/ksm: page_add_anon_rmap() -> folio_add_anon_rmap_pte()
Let's convert replace_page(). While at it, perform some folio conversion. Link: https://lkml.kernel.org/r/20231220224504.646757-19-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Peter Xu <peterx@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yin Fengwei <fengwei.yin@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Stefan Roesch
|
5088b49730 |
mm/ksm: add tracepoint for ksm advisor
This adds a new tracepoint for the ksm advisor. It reports the last scan time, the new setting of the pages_to_scan parameter and the average cpu percent usage of the ksmd background thread for the last scan. Link: https://lkml.kernel.org/r/20231218231054.1625219-4-shr@devkernel.io Signed-off-by: Stefan Roesch <shr@devkernel.io> Acked-by: David Hildenbrand <david@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Stefan Roesch
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66790e9a73 |
mm/ksm: add sysfs knobs for advisor
This adds four new knobs for the KSM advisor to influence its behaviour.
The knobs are:
- advisor_mode:
none: no advisor (default)
scan-time: scan time advisor
- advisor_max_cpu: 70 (default, cpu usage percent)
- advisor_min_pages_to_scan: 500 (default)
- advisor_max_pages_to_scan: 30000 (default)
- advisor_target_scan_time: 200 (default in seconds)
The new values will take effect on the next scan round.
Link: https://lkml.kernel.org/r/20231218231054.1625219-3-shr@devkernel.io
Signed-off-by: Stefan Roesch <shr@devkernel.io>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Stefan Roesch
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4e5fa4f5ef |
mm/ksm: add ksm advisor
Patch series "mm/ksm: Add ksm advisor", v5. What is the KSM advisor? ========================= The ksm advisor automatically manages the pages_to_scan setting to achieve a target scan time. The target scan time defines how many seconds it should take to scan all the candidate KSM pages. In other words the pages_to_scan rate is changed by the advisor to achieve the target scan time. Why do we need a KSM advisor? ============================== The number of candidate pages for KSM is dynamic. It can often be observed that during the startup of an application more candidate pages need to be processed. Without an advisor the pages_to_scan parameter needs to be sized for the maximum number of candidate pages. With the scan time advisor the pages_to_scan parameter based can be changed based on demand. Algorithm ========== The algorithm calculates the change value based on the target scan time and the previous scan time. To avoid pertubations an exponentially weighted moving average is applied. The algorithm has a max and min value to: - guarantee responsiveness to changes - to limit CPU resource consumption Parameters to influence the KSM scan advisor ============================================= The respective parameters are: - ksm_advisor_mode 0: None (default), 1: scan time advisor - ksm_advisor_target_scan_time how many seconds a scan should of all candidate pages take - ksm_advisor_max_cpu upper limit for the cpu usage in percent of the ksmd background thread The initial value and the max value for the pages_to_scan parameter can be limited with: - ksm_advisor_min_pages_to_scan minimum value for pages_to_scan per batch - ksm_advisor_max_pages_to_scan maximum value for pages_to_scan per batch The default settings for the above two parameters should be suitable for most workloads. The parameters are exposed as knobs in /sys/kernel/mm/ksm. By default the scan time advisor is disabled. Currently there are two advisors: - none and - scan-time. Resource savings ================= Tests with various workloads have shown considerable CPU savings. Most of the workloads I have investigated have more candidate pages during startup. Once the workload is stable in terms of memory, the number of candidate pages is reduced. Without the advisor, the pages_to_scan needs to be sized for the maximum number of candidate pages. So having this advisor definitely helps in reducing CPU consumption. For the instagram workload, the advisor achieves a 25% CPU reduction. Once the memory is stable, the pages_to_scan parameter gets reduced to about 40% of its max value. The new advisor works especially well if the smart scan feature is also enabled. How is defining a target scan time better? =========================================== For an administrator it is more logical to set a target scan time.. The administrator can determine how many pages are scanned on each scan. Therefore setting a target scan time makes more sense. In addition the administrator might have a good idea about the memory sizing of its respective workloads. Setting cpu limits is easier than setting The pages_to_scan parameter. The pages_to_scan parameter is per batch. For the administrator it is difficult to set the pages_to_scan parameter. Tracing ======= A new tracing event has been added for the scan time advisor. The new trace event is called ksm_advisor. It reports the scan time, the new pages_to_scan setting and the cpu usage of the ksmd background thread. Other approaches ================= Approach 1: Adapt pages_to_scan after processing each batch. If KSM merges pages, increase the scan rate, if less KSM pages, reduce the the pages_to_scan rate. This doesn't work too well. While it increases the pages_to_scan for a short period, but generally it ends up with a too low pages_to_scan rate. Approach 2: Adapt pages_to_scan after each scan. The problem with that approach is that the calculated scan rate tends to be high. The more aggressive KSM scans, the more pages it can de-duplicate. There have been earlier attempts at an advisor: propose auto-run mode of ksm and its tests (https://marc.info/?l=linux-mm&m=166029880214485&w=2) This patch (of 5): This adds the ksm advisor. The ksm advisor automatically manages the pages_to_scan setting to achieve a target scan time. The target scan time defines how many seconds it should take to scan all the candidate KSM pages. In other words the pages_to_scan rate is changed by the advisor to achieve the target scan time. The algorithm has a max and min value to: - guarantee responsiveness to changes - limit CPU resource consumption The respective parameters are: - ksm_advisor_target_scan_time (how many seconds a scan should take) - ksm_advisor_max_cpu (maximum value for cpu percent usage) - ksm_advisor_min_pages (minimum value for pages_to_scan per batch) - ksm_advisor_max_pages (maximum value for pages_to_scan per batch) The algorithm calculates the change value based on the target scan time and the previous scan time. To avoid pertubations an exponentially weighted moving average is applied. The advisor is managed by two main parameters: target scan time, cpu max time for the ksmd background thread. These parameters determine how aggresive ksmd scans. In addition there are min and max values for the pages_to_scan parameter to make sure that its initial and max values are not set too low or too high. This ensures that it is able to react to changes quickly enough. The default values are: - target scan time: 200 secs - max cpu: 70% - min pages: 500 - max pages: 30000 By default the advisor is disabled. Currently there are two advisors: none and scan-time. Tests with various workloads have shown considerable CPU savings. Most of the workloads I have investigated have more candidate pages during startup, once the workload is stable in terms of memory, the number of candidate pages is reduced. Without the advisor, the pages_to_scan needs to be sized for the maximum number of candidate pages. So having this advisor definitely helps in reducing CPU consumption. For the instagram workload, the advisor achieves a 25% CPU reduction. Once the memory is stable, the pages_to_scan parameter gets reduced to about 40% of its max value. Link: https://lkml.kernel.org/r/20231218231054.1625219-1-shr@devkernel.io Link: https://lkml.kernel.org/r/20231218231054.1625219-2-shr@devkernel.io Signed-off-by: Stefan Roesch <shr@devkernel.io> Acked-by: David Hildenbrand <david@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Rik van Riel <riel@surriel.com> Cc: Stefan Roesch <shr@devkernel.io> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Matthew Wilcox (Oracle)
|
96db66d9c8 |
mm: convert ksm_might_need_to_copy() to work on folios
Patch series "Finish two folio conversions". Most callers of page_add_new_anon_rmap() and lru_cache_add_inactive_or_unevictable() have been converted to their folio equivalents, but there are still a few stragglers. There's a bit of preparatory work in ksm and unuse_pte(), but after that it's pretty mechanical. This patch (of 9): Accept a folio as an argument and return a folio result. Removes a call to compound_head() in do_swap_page(), and prevents folio & page from getting out of sync in unuse_pte(). Reviewed-by: David Hildenbrand <david@redhat.com> [willy@infradead.org: fix smatch warning] Link: https://lkml.kernel.org/r/ZXnPtblC6A1IkyAB@casper.infradead.org [david@redhat.com: only adjust the page if the folio changed] Link: https://lkml.kernel.org/r/6a8f2110-fa91-4c10-9eae-88315309a6e3@redhat.com Link: https://lkml.kernel.org/r/20231211162214.2146080-1-willy@infradead.org Link: https://lkml.kernel.org/r/20231211162214.2146080-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: David Hildenbrand <david@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kevin Hao
|
f55afd954c |
mm: ksm: remove unnecessary try_to_freeze()
A freezable kernel thread can enter frozen state during freezing by either calling try_to_freeze() or using wait_event_freezable() and its variants. However, there is no need to use both methods simultaneously. Link: https://lkml.kernel.org/r/20231213090906.1070985-1-haokexin@gmail.com Signed-off-by: Kevin Hao <haokexin@gmail.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Pavel Machek <pavel@ucw.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kefeng Wang
|
1486fb5013 |
mm: ksm: use more folio api in ksm_might_need_to_copy()
Patch series "mm: cleanup and use more folio in page fault", v3. Rename page_copy_prealloc() to folio_prealloc(), which is used by more functions, also do more folio conversion in page fault. This patch (of 5): Since ksm only support normal page, no swapout/in for ksm large folio too, add large folio check in ksm_might_need_to_copy(), also convert page->index to folio->index as page->index is going away. Then convert ksm_might_need_to_copy() to use more folio api to save nine compound_head() calls, short 'address' to reduce max-line-length. Link: https://lkml.kernel.org/r/20231118023232.1409103-1-wangkefeng.wang@huawei.com Link: https://lkml.kernel.org/r/20231118023232.1409103-2-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: David Hildenbrand <david@redhat.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com> Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Fabio M. De Francesco
|
b335198966 |
mm/ksm: use kmap_local_page() in calc_checksum()
kmap_atomic() has been deprecated in favor of kmap_local_page(). Therefore, replace kmap_atomic() with kmap_local_page() in calc_checksum(). kmap_atomic() is implemented like a kmap_local_page() which also disables page-faults and preemption (the latter only in !PREEMPT_RT kernels). The kernel virtual addresses returned by these two API are only valid in the context of the callers (i.e., they cannot be handed to other threads). With kmap_local_page() the mappings are per thread and CPU local like in kmap_atomic(); however, they can handle page-faults and can be called from any context (including interrupts). The tasks that call kmap_local_page() can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. In calc_checksum(), the block of code between the mapping and un-mapping does not depend on the above-mentioned side effects of kmap_aatomic(), so that a mere replacements of the old API with the new one is all that is required (i.e., there is no need to explicitly call pagefault_disable() and/or preempt_disable()). Link: https://lkml.kernel.org/r/20231120141855.6761-1-fmdefrancesco@gmail.com Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com> Cc: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Ryan Roberts
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afccb0804f |
mm: more ptep_get() conversion
Commit
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Stefan Roesch
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e5a6899126 |
mm/ksm: add pages_skipped metric
This change adds the "pages skipped" metric. To be able to evaluate how successful smart page scanning is, the pages skipped metric can be compared to the pages scanned metric. The pages skipped metric is a cumulative counter. The counter is stored under /sys/kernel/mm/ksm/pages_skipped. Link: https://lkml.kernel.org/r/20230926040939.516161-3-shr@devkernel.io Signed-off-by: Stefan Roesch <shr@devkernel.io> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Stefan Roesch
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5e924ff54d |
mm/ksm: add "smart" page scanning mode
Patch series "Smart scanning mode for KSM", v3. This patch series adds "smart scanning" for KSM. What is smart scanning? ======================= KSM evaluates all the candidate pages for each scan. It does not use historic information from previous scans. This has the effect that candidate pages that couldn't be used for KSM de-duplication continue to be evaluated for each scan. The idea of "smart scanning" is to keep historic information. With the historic information we can temporarily skip the candidate page for one or several scans. Details: ======== "Smart scanning" is to keep two small counters to store if the page has been used for KSM. One counter stores how often we already tried to use the page for KSM and the other counter stores how often we skip a page. How often we skip the candidate page depends how often a page failed KSM de-duplication. The code skips a maximum of 8 times. During testing this has shown to be a good compromise for different workloads. New sysfs knob: =============== Smart scanning is not enabled by default. With /sys/kernel/mm/ksm/smart_scan smart scanning can be enabled. Monitoring: =========== To monitor how effective smart scanning is a new sysfs knob has been introduced. /sys/kernel/mm/pages_skipped report how many pages have been skipped by smart scanning. Results: ======== - Various workloads have shown a 20% - 25% reduction in page scans For the instagram workload for instance, the number of pages scanned has been reduced from over 20M pages per scan to less than 15M pages. - Less pages scans also resulted in an overall higher de-duplication rate as some shorter lived pages could be de-duplicated additionally - Less pages scanned allows to reduce the pages_to_scan parameter and this resulted in a 25% reduction in terms of CPU. - The improvements have been observed for workloads that enable KSM with madvise as well as prctl This patch (of 4): This change adds a "smart" page scanning mode for KSM. So far all the candidate pages are continuously scanned to find candidates for de-duplication. There are a considerably number of pages that cannot be de-duplicated. This is costly in terms of CPU. By using smart scanning considerable CPU savings can be achieved. This change takes the history of scanning pages into account and skips the page scanning of certain pages for a while if de-deduplication for this page has not been successful in the past. To do this it introduces two new fields in the ksm_rmap_item structure: age and remaining_skips. age, is the KSM age and remaining_skips determines how often scanning of this page is skipped. The age field is incremented each time the page is scanned and the page cannot be de- duplicated. age updated is capped at U8_MAX. How often a page is skipped is dependent how often de-duplication has been tried so far and the number of skips is currently limited to 8. This value has shown to be effective with different workloads. The feature is currently disable by default and can be enabled with the new smart_scan knob. The feature has shown to be very effective: upt to 25% of the page scans can be eliminated; the pages_to_scan rate can be reduced by 40 - 50% and a similar de-duplication rate can be maintained. [akpm@linux-foundation.org: make ksm_smart_scan default true, for testing] Link: https://lkml.kernel.org/r/20230926040939.516161-1-shr@devkernel.io Link: https://lkml.kernel.org/r/20230926040939.516161-2-shr@devkernel.io Signed-off-by: Stefan Roesch <shr@devkernel.io> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Rik van Riel <riel@surriel.com> Cc: Stefan Roesch <shr@devkernel.io> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Tong Tiangen
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d256d1cd8d |
mm: memory-failure: use rcu lock instead of tasklist_lock when collect_procs()
We found a softlock issue in our test, analyzed the logs, and found that
the relevant CPU call trace as follows:
CPU0:
_do_fork
-> copy_process()
-> write_lock_irq(&tasklist_lock) //Disable irq,waiting for
//tasklist_lock
CPU1:
wp_page_copy()
->pte_offset_map_lock()
-> spin_lock(&page->ptl); //Hold page->ptl
-> ptep_clear_flush()
-> flush_tlb_others() ...
-> smp_call_function_many()
-> arch_send_call_function_ipi_mask()
-> csd_lock_wait() //Waiting for other CPUs respond
//IPI
CPU2:
collect_procs_anon()
-> read_lock(&tasklist_lock) //Hold tasklist_lock
->for_each_process(tsk)
-> page_mapped_in_vma()
-> page_vma_mapped_walk()
-> map_pte()
->spin_lock(&page->ptl) //Waiting for page->ptl
We can see that CPU1 waiting for CPU0 respond IPI，CPU0 waiting for CPU2
unlock tasklist_lock, CPU2 waiting for CPU1 unlock page->ptl. As a result,
softlockup is triggered.
For collect_procs_anon(), what we're doing is task list iteration, during
the iteration, with the help of call_rcu(), the task_struct object is freed
only after one or more grace periods elapse. the logic as follows:
release_task()
-> __exit_signal()
-> __unhash_process()
-> list_del_rcu()
-> put_task_struct_rcu_user()
-> call_rcu(&task->rcu, delayed_put_task_struct)
delayed_put_task_struct()
-> put_task_struct()
-> if (refcount_sub_and_test())
__put_task_struct()
-> free_task()
Therefore, under the protection of the rcu lock, we can safely use
get_task_struct() to ensure a safe reference to task_struct during the
iteration.
By removing the use of tasklist_lock in task list iteration, we can break
the softlock chain above.
The same logic can also be applied to:
- collect_procs_file()
- collect_procs_fsdax()
- collect_procs_ksm()
Link: https://lkml.kernel.org/r/20230828022527.241693-1-tongtiangen@huawei.com
Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Andrew Morton
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5994eabf3b | merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes | ||
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Stefan Roesch
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b348b5fe2b |
mm/ksm: add pages scanned metric
ksm currently maintains several statistics, which let you determine how successful KSM is at sharing pages. However it does not contain a metric to determine how much work it does. This commit adds the pages scanned metric. This allows the administrator to determine how many pages have been scanned over a period of time. Link: https://lkml.kernel.org/r/20230811193655.2518943-1-shr@devkernel.io Signed-off-by: Stefan Roesch <shr@devkernel.io> Acked-by: David Hildenbrand <david@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Suren Baghdasaryan
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49b0638502 |
mm: enable page walking API to lock vmas during the walk
walk_page_range() and friends often operate under write-locked mmap_lock. With introduction of vma locks, the vmas have to be locked as well during such walks to prevent concurrent page faults in these areas. Add an additional member to mm_walk_ops to indicate locking requirements for the walk. The change ensures that page walks which prevent concurrent page faults by write-locking mmap_lock, operate correctly after introduction of per-vma locks. With per-vma locks page faults can be handled under vma lock without taking mmap_lock at all, so write locking mmap_lock would not stop them. The change ensures vmas are properly locked during such walks. A sample issue this solves is do_mbind() performing queue_pages_range() to queue pages for migration. Without this change a concurrent page can be faulted into the area and be left out of migration. Link: https://lkml.kernel.org/r/20230804152724.3090321-2-surenb@google.com Signed-off-by: Suren Baghdasaryan <surenb@google.com> Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org> Suggested-by: Jann Horn <jannh@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Laurent Dufour <ldufour@linux.ibm.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Michel Lespinasse <michel@lespinasse.org> Cc: Peter Xu <peterx@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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xu xin
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1a8e843057 |
ksm: consider KSM-placed zeropages when calculating KSM profit
When use_zero_pages is enabled, the calculation of ksm profit is not correct because ksm zero pages is not counted in. So update the calculation of KSM profit including the documentation. Link: https://lkml.kernel.org/r/20230613030942.186041-1-yang.yang29@zte.com.cn Signed-off-by: xu xin <xu.xin16@zte.com.cn> Acked-by: David Hildenbrand <david@redhat.com> Cc: Xiaokai Ran <ran.xiaokai@zte.com.cn> Cc: Yang Yang <yang.yang29@zte.com.cn> Cc: Jiang Xuexin <jiang.xuexin@zte.com.cn> Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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xu xin
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6080d19f07 |
ksm: add ksm zero pages for each process
As the number of ksm zero pages is not included in ksm_merging_pages per process when enabling use_zero_pages, it's unclear of how many actual pages are merged by KSM. To let users accurately estimate their memory demands when unsharing KSM zero-pages, it's necessary to show KSM zero- pages per process. In addition, it help users to know the actual KSM profit because KSM-placed zero pages are also benefit from KSM. since unsharing zero pages placed by KSM accurately is achieved, then tracking empty pages merging and unmerging is not a difficult thing any longer. Since we already have /proc/<pid>/ksm_stat, just add the information of 'ksm_zero_pages' in it. Link: https://lkml.kernel.org/r/20230613030938.185993-1-yang.yang29@zte.com.cn Signed-off-by: xu xin <xu.xin16@zte.com.cn> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn> Reviewed-by: Yang Yang <yang.yang29@zte.com.cn> Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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xu xin
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e2942062e0 |
ksm: count all zero pages placed by KSM
As pages_sharing and pages_shared don't include the number of zero pages merged by KSM, we cannot know how many pages are zero pages placed by KSM when enabling use_zero_pages, which leads to KSM not being transparent with all actual merged pages by KSM. In the early days of use_zero_pages, zero-pages was unable to get unshared by the ways like MADV_UNMERGEABLE so it's hard to count how many times one of those zeropages was then unmerged. But now, unsharing KSM-placed zero page accurately has been achieved, so we can easily count both how many times a page full of zeroes was merged with zero-page and how many times one of those pages was then unmerged. and so, it helps to estimate memory demands when each and every shared page could get unshared. So we add ksm_zero_pages under /sys/kernel/mm/ksm/ to show the number of all zero pages placed by KSM. Meanwhile, we update the Documentation. Link: https://lkml.kernel.org/r/20230613030934.185944-1-yang.yang29@zte.com.cn Signed-off-by: xu xin <xu.xin16@zte.com.cn> Acked-by: David Hildenbrand <david@redhat.com> Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn> Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn> Reviewed-by: Yang Yang <yang.yang29@zte.com.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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xu xin
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79271476b3 |
ksm: support unsharing KSM-placed zero pages
Patch series "ksm: support tracking KSM-placed zero-pages", v10. The core idea of this patch set is to enable users to perceive the number of any pages merged by KSM, regardless of whether use_zero_page switch has been turned on, so that users can know how much free memory increase is really due to their madvise(MERGEABLE) actions. But the problem is, when enabling use_zero_pages, all empty pages will be merged with kernel zero pages instead of with each other as use_zero_pages is disabled, and then these zero-pages are no longer monitored by KSM. The motivations to do this is seen at: https://lore.kernel.org/lkml/202302100915227721315@zte.com.cn/ In one word, we hope to implement the support for KSM-placed zero pages tracking without affecting the feature of use_zero_pages, so that app developer can also benefit from knowing the actual KSM profit by getting KSM-placed zero pages to optimize applications eventually when /sys/kernel/mm/ksm/use_zero_pages is enabled. This patch (of 5): When use_zero_pages of ksm is enabled, madvise(addr, len, MADV_UNMERGEABLE) and other ways (like write 2 to /sys/kernel/mm/ksm/run) to trigger unsharing will *not* actually unshare the shared zeropage as placed by KSM (which is against the MADV_UNMERGEABLE documentation). As these KSM-placed zero pages are out of the control of KSM, the related counts of ksm pages don't expose how many zero pages are placed by KSM (these special zero pages are different from those initially mapped zero pages, because the zero pages mapped to MADV_UNMERGEABLE areas are expected to be a complete and unshared page). To not blindly unshare all shared zero_pages in applicable VMAs, the patch use pte_mkdirty (related with architecture) to mark KSM-placed zero pages. Thus, MADV_UNMERGEABLE will only unshare those KSM-placed zero pages. In addition, we'll reuse this mechanism to reliably identify KSM-placed ZeroPages to properly account for them (e.g., calculating the KSM profit that includes zeropages) in the latter patches. The patch will not degrade the performance of use_zero_pages as it doesn't change the way of merging empty pages in use_zero_pages's feature. Link: https://lkml.kernel.org/r/202306131104554703428@zte.com.cn Link: https://lkml.kernel.org/r/20230613030928.185882-1-yang.yang29@zte.com.cn Signed-off-by: xu xin <xu.xin16@zte.com.cn> Acked-by: David Hildenbrand <david@redhat.com> Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn> Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn> Reviewed-by: Yang Yang <yang.yang29@zte.com.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Miaohe Lin
|
f985fc3220 |
mm/swapfile: fix wrong swap entry type for hwpoisoned swapcache page
Patch series "A few fixup patches for mm", v2.
This series contains a few fixup patches to fix potential unexpected
return value, fix wrong swap entry type for hwpoisoned swapcache page and
so on. More details can be found in the respective changelogs.
This patch (of 3):
Hwpoisoned dirty swap cache page is kept in the swap cache and there's
simple interception code in do_swap_page() to catch it. But when trying
to swapoff, unuse_pte() will wrongly install a general sense of "future
accesses are invalid" swap entry for hwpoisoned swap cache page due to
unaware of such type of page. The user will receive SIGBUS signal without
expected BUS_MCEERR_AR payload. BTW, typo 'hwposioned' is fixed.
Link: https://lkml.kernel.org/r/20230727115643.639741-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20230727115643.639741-2-linmiaohe@huawei.com
Fixes:
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Matthew Wilcox (Oracle)
|
1fec6890bf |
mm: remove references to pagevec
Most of these should just refer to the LRU cache rather than the data structure used to implement the LRU cache. Link: https://lkml.kernel.org/r/20230621164557.3510324-13-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Ryan Roberts
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c33c794828 |
mm: ptep_get() conversion
Convert all instances of direct pte_t* dereferencing to instead use ptep_get() helper. This means that by default, the accesses change from a C dereference to a READ_ONCE(). This is technically the correct thing to do since where pgtables are modified by HW (for access/dirty) they are volatile and therefore we should always ensure READ_ONCE() semantics. But more importantly, by always using the helper, it can be overridden by the architecture to fully encapsulate the contents of the pte. Arch code is deliberately not converted, as the arch code knows best. It is intended that arch code (arm64) will override the default with its own implementation that can (e.g.) hide certain bits from the core code, or determine young/dirty status by mixing in state from another source. Conversion was done using Coccinelle: ---- // $ make coccicheck \ // COCCI=ptepget.cocci \ // SPFLAGS="--include-headers" \ // MODE=patch virtual patch @ depends on patch @ pte_t *v; @@ - *v + ptep_get(v) ---- Then reviewed and hand-edited to avoid multiple unnecessary calls to ptep_get(), instead opting to store the result of a single call in a variable, where it is correct to do so. This aims to negate any cost of READ_ONCE() and will benefit arch-overrides that may be more complex. Included is a fix for an issue in an earlier version of this patch that was pointed out by kernel test robot. The issue arose because config MMU=n elides definition of the ptep helper functions, including ptep_get(). HUGETLB_PAGE=n configs still define a simple huge_ptep_clear_flush() for linking purposes, which dereferences the ptep. So when both configs are disabled, this caused a build error because ptep_get() is not defined. Fix by continuing to do a direct dereference when MMU=n. This is safe because for this config the arch code cannot be trying to virtualize the ptes because none of the ptep helpers are defined. Link: https://lkml.kernel.org/r/20230612151545.3317766-4-ryan.roberts@arm.com Reported-by: kernel test robot <lkp@intel.com> Link: https://lore.kernel.org/oe-kbuild-all/202305120142.yXsNEo6H-lkp@intel.com/ Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Potapenko <glider@google.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Dave Airlie <airlied@gmail.com> Cc: Dimitri Sivanich <dimitri.sivanich@hpe.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Ian Rogers <irogers@google.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: SeongJae Park <sj@kernel.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Yu Zhao <yuzhao@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Hugh Dickins
|
04dee9e85c |
mm/various: give up if pte_offset_map[_lock]() fails
Following the examples of nearby code, various functions can just give up if pte_offset_map() or pte_offset_map_lock() fails. And there's no need for a preliminary pmd_trans_unstable() or other such check, since such cases are now safely handled inside. Link: https://lkml.kernel.org/r/7b9bd85d-1652-cbf2-159d-f503b45e5b@google.com Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Christoph Hellwig <hch@infradead.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Qi Zheng <zhengqi.arch@bytedance.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: SeongJae Park <sj@kernel.org> Cc: Song Liu <song@kernel.org> Cc: Steven Price <steven.price@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Cc: Will Deacon <will@kernel.org> Cc: Yang Shi <shy828301@gmail.com> Cc: Yu Zhao <yuzhao@google.com> Cc: Zack Rusin <zackr@vmware.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Hugh Dickins
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26e1a0c327 |
mm: use pmdp_get_lockless() without surplus barrier()
Patch series "mm: allow pte_offset_map[_lock]() to fail", v2. What is it all about? Some mmap_lock avoidance i.e. latency reduction. Initially just for the case of collapsing shmem or file pages to THPs; but likely to be relied upon later in other contexts e.g. freeing of empty page tables (but that's not work I'm doing). mmap_write_lock avoidance when collapsing to anon THPs? Perhaps, but again that's not work I've done: a quick attempt was not as easy as the shmem/file case. I would much prefer not to have to make these small but wide-ranging changes for such a niche case; but failed to find another way, and have heard that shmem MADV_COLLAPSE's usefulness is being limited by that mmap_write_lock it currently requires. These changes (though of course not these exact patches) have been in Google's data centre kernel for three years now: we do rely upon them. What is this preparatory series about? The current mmap locking will not be enough to guard against that tricky transition between pmd entry pointing to page table, and empty pmd entry, and pmd entry pointing to huge page: pte_offset_map() will have to validate the pmd entry for itself, returning NULL if no page table is there. What to do about that varies: sometimes nearby error handling indicates just to skip it; but in many cases an ACTION_AGAIN or "goto again" is appropriate (and if that risks an infinite loop, then there must have been an oops, or pfn 0 mistaken for page table, before). Given the likely extension to freeing empty page tables, I have not limited this set of changes to a THP config; and it has been easier, and sets a better example, if each site is given appropriate handling: even where deeper study might prove that failure could only happen if the pmd table were corrupted. Several of the patches are, or include, cleanup on the way; and by the end, pmd_trans_unstable() and suchlike are deleted: pte_offset_map() and pte_offset_map_lock() then handle those original races and more. Most uses of pte_lockptr() are deprecated, with pte_offset_map_nolock() taking its place. This patch (of 32): Use pmdp_get_lockless() in preference to READ_ONCE(*pmdp), to get a more reliable result with PAE (or READ_ONCE as before without PAE); and remove the unnecessary extra barrier()s which got left behind in its callers. HOWEVER: Note the small print in linux/pgtable.h, where it was designed specifically for fast GUP, and depends on interrupts being disabled for its full guarantee: most callers which have been added (here and before) do NOT have interrupts disabled, so there is still some need for caution. Link: https://lkml.kernel.org/r/f35279a9-9ac0-de22-d245-591afbfb4dc@google.com Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Yu Zhao <yuzhao@google.com> Acked-by: Peter Xu <peterx@redhat.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Christoph Hellwig <hch@infradead.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Qi Zheng <zhengqi.arch@bytedance.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: SeongJae Park <sj@kernel.org> Cc: Song Liu <song@kernel.org> Cc: Steven Price <steven.price@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Cc: Will Deacon <will@kernel.org> Cc: Yang Shi <shy828301@gmail.com> Cc: Zack Rusin <zackr@vmware.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |