Instead of declaring a struct page_vma_mapped_walk directly,
use these helpers to allow us to transition to a PFN approach in the
following patches.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
DAMON's virtual address spaces monitoring primitive uses 'struct pid *'
of the target process as its monitoring target id. The kernel address
is exposed as-is to the user space via the DAMON tracepoint,
'damon_aggregated'.
Though primarily only privileged users are allowed to access that, it
would be better to avoid unnecessarily exposing kernel pointers so.
Because the trace result is only required to be able to distinguish each
target, we aren't need to use the pointer as-is.
This makes the tracepoint to use the index of the target in the
context's targets list as its id in the tracepoint, to hide the kernel
space address.
Link: https://lkml.kernel.org/r/20211229131016.23641-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Usually, inline function is declared static since it should sit between
storage and type. And implement it in a header file if used by multiple
files.
And this change also fixes compile issue when backport damon to 5.10.
mm/damon/vaddr.c: In function `damon_va_evenly_split_region':
./include/linux/damon.h:425:13: error: inlining failed in call to `always_inline' `damon_insert_region': function body not available
425 | inline void damon_insert_region(struct damon_region *r,
| ^~~~~~~~~~~~~~~~~~~
mm/damon/vaddr.c:86:3: note: called from here
86 | damon_insert_region(n, r, next, t);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Link: https://lkml.kernel.org/r/20211223085703.6142-1-guoqing.jiang@linux.dev
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The process's VMAs can be mapped by hugetlb page, but now the DAMON did
not implement the access checking for hugetlb pte, so we can not get the
actual access count like below if a process VMAs were mapped by hugetlb.
damon_aggregated: target_id=18446614368406014464 nr_regions=12 4194304-5476352: 0 545
damon_aggregated: target_id=18446614368406014464 nr_regions=12 140662370467840-140662372970496: 0 545
damon_aggregated: target_id=18446614368406014464 nr_regions=12 140662372970496-140662375460864: 0 545
damon_aggregated: target_id=18446614368406014464 nr_regions=12 140662375460864-140662377951232: 0 545
damon_aggregated: target_id=18446614368406014464 nr_regions=12 140662377951232-140662380449792: 0 545
damon_aggregated: target_id=18446614368406014464 nr_regions=12 140662380449792-140662382944256: 0 545
......
Thus this patch adds hugetlb access checking support, with this patch we
can see below VMA mapped by hugetlb access count.
damon_aggregated: target_id=18446613056935405824 nr_regions=12 140296486649856-140296489914368: 1 3
damon_aggregated: target_id=18446613056935405824 nr_regions=12 140296489914368-140296492978176: 1 3
damon_aggregated: target_id=18446613056935405824 nr_regions=12 140296492978176-140296495439872: 1 3
damon_aggregated: target_id=18446613056935405824 nr_regions=12 140296495439872-140296498311168: 1 3
damon_aggregated: target_id=18446613056935405824 nr_regions=12 140296498311168-140296501198848: 1 3
damon_aggregated: target_id=18446613056935405824 nr_regions=12 140296501198848-140296504320000: 1 3
damon_aggregated: target_id=18446613056935405824 nr_regions=12 140296504320000-140296507568128: 1 2
......
[baolin.wang@linux.alibaba.com: fix unused var warning]
Link: https://lkml.kernel.org/r/1aaf9c11-0d8e-b92d-5c92-46e50a6e8d4e@linux.alibaba.com
[baolin.wang@linux.alibaba.com: v3]
Link: https://lkml.kernel.org/r/486927ecaaaecf2e3a7fbe0378ec6e1c58b50747.1640852276.git.baolin.wang@linux.alibaba.com
Link: https://lkml.kernel.org/r/6afcbd1fda5f9c7c24f320d26a98188c727ceec3.1639623751.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If the time/space quotas of a given DAMON-based operation scheme is too
small, the scheme could show unexpectedly slow progress. However, there
is no good way to notice the case in runtime. This commit extends the
DAMOS stat to provide how many times the quota limits exceeded so that
the users can easily notice the case and tune the scheme.
Link: https://lkml.kernel.org/r/20211210150016.35349-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm/damon/schemes: Extend stats for better online analysis and tuning".
To help online access pattern analysis and tuning of DAMON-based
Operation Schemes (DAMOS), DAMOS provides simple statistics for each
scheme. Introduction of DAMOS time/space quota further made the tuning
easier by making the risk management easier. However, that also made
understanding of the working schemes a little bit more difficult.
For an example, progress of a given scheme can now be throttled by not
only the aggressiveness of the target access pattern, but also the
time/space quotas. So, when a scheme is showing unexpectedly slow
progress, it's difficult to know by what the progress of the scheme is
throttled, with currently provided statistics.
This patchset extends the statistics to contain some metrics that can be
helpful for such online schemes analysis and tuning (patches 1-2),
exports those to users (patches 3 and 5), and add documents (patches 4
and 6).
This patch (of 6):
DAMON-based operation schemes (DAMOS) stats provide only the number and
the amount of regions that the action of the scheme has tried to be
applied. Because the action could be failed for some reasons, the
currently provided information is sometimes not useful or convenient
enough for schemes profiling and tuning. To improve this situation,
this commit extends the DAMOS stats to provide the number and the amount
of regions that the action has successfully applied.
Link: https://lkml.kernel.org/r/20211210150016.35349-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211210150016.35349-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm/damon: Do some small changes", v4.
This patch (of 4):
In damon/paddr.c file, two functions names start with underscore,
static void __damon_pa_prepare_access_check(struct damon_ctx *ctx,
struct damon_region *r)
static void __damon_pa_prepare_access_check(struct damon_ctx *ctx,
struct damon_region *r)
In damon/vaddr.c file, there are also two functions with the same function,
static void damon_va_prepare_access_check(struct damon_ctx *ctx,
struct mm_struct *mm, struct damon_region *r)
static void damon_va_check_access(struct damon_ctx *ctx,
struct mm_struct *mm, struct damon_region *r)
It makes sense to keep consistent, and it is not easy to be confused with
the function that call them.
Link: https://lkml.kernel.org/r/cover.1636989871.git.xhao@linux.alibaba.com
Link: https://lkml.kernel.org/r/529054aed932a42b9c09fc9977ad4574b9e7b0bd.1636989871.git.xhao@linux.alibaba.com
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DAMON debugfs interface increases the reference counts of 'struct pid's
for targets from the 'target_ids' file write callback
('dbgfs_target_ids_write()'), but decreases the counts only in DAMON
monitoring termination callback ('dbgfs_before_terminate()').
Therefore, when 'target_ids' file is repeatedly written without DAMON
monitoring start/termination, the reference count is not decreased and
therefore memory for the 'struct pid' cannot be freed. This commit
fixes this issue by decreasing the reference counts when 'target_ids' is
written.
Link: https://lkml.kernel.org/r/20211229124029.23348-1-sj@kernel.org
Fixes: 4bc05954d0 ("mm/damon: implement a debugfs-based user space interface")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> [5.15+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DAMON debugfs interface iterates current monitoring targets in
'dbgfs_target_ids_read()' while holding the corresponding
'kdamond_lock'. However, it also destructs the monitoring targets in
'dbgfs_before_terminate()' without holding the lock. This can result in
a use_after_free bug. This commit avoids the race by protecting the
destruction with the corresponding 'kdamond_lock'.
Link: https://lkml.kernel.org/r/20211221094447.2241-1-sj@kernel.org
Reported-by: Sangwoo Bae <sangwoob@amazon.com>
Fixes: 4bc05954d0 ("mm/damon: implement a debugfs-based user space interface")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> [5.15.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DAMON core prints error messages when damon_target object creation is
failed or wrong monitoring attributes are given. Because appropriate
error code is returned for each case, the messages are not essential.
Also, because the code path can be triggered with user-specified input,
this could result in kernel log mistakenly being messy. To avoid the
case, this commit removes the messages.
Link: https://lkml.kernel.org/r/20211201150440.1088-4-sj@kernel.org
Fixes: 4bc05954d0 ("mm/damon: implement a debugfs-based user space interface")
Fixes: b9a6ac4e4e ("mm/damon: adaptively adjust regions")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When wrong scheme action is requested via the debugfs interface, DAMON
prints an error message. Because the function returns error code, this
is not really needed. Because the code path is triggered by the user
specified input, this can result in kernel log mistakenly being messy.
To avoid the case, this commit removes the message.
Link: https://lkml.kernel.org/r/20211201150440.1088-3-sj@kernel.org
Fixes: af122dd8f3 ("mm/damon/dbgfs: support DAMON-based Operation Schemes")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm/damon: Trivial fixups and improvements".
This patchset contains trivial fixups and improvements for DAMON and its
kunit/kselftest tests.
This patch (of 11):
DAMON is using hrtimer if requested sleep time is <=100ms, while the
suggested threshold[1] is <=20ms. This commit applies the threshold.
[1] Documentation/timers/timers-howto.rst
Link: https://lkml.kernel.org/r/20211201150440.1088-2-sj@kernel.org
Fixes: ee801b7dd7 ("mm/damon/schemes: activate schemes based on a watermarks mechanism")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Daniel Borkmann says:
====================
bpf 2021-12-08
We've added 12 non-merge commits during the last 22 day(s) which contain
a total of 29 files changed, 659 insertions(+), 80 deletions(-).
The main changes are:
1) Fix an off-by-two error in packet range markings and also add a batch of
new tests for coverage of these corner cases, from Maxim Mikityanskiy.
2) Fix a compilation issue on MIPS JIT for R10000 CPUs, from Johan Almbladh.
3) Fix two functional regressions and a build warning related to BTF kfunc
for modules, from Kumar Kartikeya Dwivedi.
4) Fix outdated code and docs regarding BPF's migrate_disable() use on non-
PREEMPT_RT kernels, from Sebastian Andrzej Siewior.
5) Add missing includes in order to be able to detangle cgroup vs bpf header
dependencies, from Jakub Kicinski.
6) Fix regression in BPF sockmap tests caused by missing detachment of progs
from sockets when they are removed from the map, from John Fastabend.
7) Fix a missing "no previous prototype" warning in x86 JIT caused by BPF
dispatcher, from Björn Töpel.
* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
bpf: Add selftests to cover packet access corner cases
bpf: Fix the off-by-two error in range markings
treewide: Add missing includes masked by cgroup -> bpf dependency
tools/resolve_btfids: Skip unresolved symbol warning for empty BTF sets
bpf: Fix bpf_check_mod_kfunc_call for built-in modules
bpf: Make CONFIG_DEBUG_INFO_BTF depend upon CONFIG_BPF_SYSCALL
mips, bpf: Fix reference to non-existing Kconfig symbol
bpf: Make sure bpf_disable_instrumentation() is safe vs preemption.
Documentation/locking/locktypes: Update migrate_disable() bits.
bpf, sockmap: Re-evaluate proto ops when psock is removed from sockmap
bpf, sockmap: Attach map progs to psock early for feature probes
bpf, x86: Fix "no previous prototype" warning
====================
Link: https://lore.kernel.org/r/20211208155125.11826-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Patch series "DAMON fixes".
This patch (of 2):
DAMON users can trigger below warning in '__alloc_pages()' by invoking
write() to some DAMON debugfs files with arbitrarily high count
argument, because DAMON debugfs interface allocates some buffers based
on the user-specified 'count'.
if (unlikely(order >= MAX_ORDER)) {
WARN_ON_ONCE(!(gfp & __GFP_NOWARN));
return NULL;
}
Because the DAMON debugfs interface code checks failure of the
'kmalloc()', this commit simply suppresses the warnings by adding
'__GFP_NOWARN' flag.
Link: https://lkml.kernel.org/r/20211110145758.16558-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211110145758.16558-2-sj@kernel.org
Fixes: 4bc05954d0 ("mm/damon: implement a debugfs-based user space interface")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When the ctx->adaptive_targets list is empty, I did some test on
monitor_on interface like this.
# cat /sys/kernel/debug/damon/target_ids
#
# echo on > /sys/kernel/debug/damon/monitor_on
# damon: kdamond (5390) starts
Though the ctx->adaptive_targets list is empty, but the kthread_run
still be called, and the kdamond.x thread still be created, this is
meaningless.
So there adds a judgment in 'dbgfs_monitor_on_write', if the
ctx->adaptive_targets list is empty, return -EINVAL.
Link: https://lkml.kernel.org/r/0a60a6e8ec9d71989e0848a4dc3311996ca3b5d4.1634720326.git.xhao@linux.alibaba.com
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DAMON-based operation schemes need to be manually turned on and off. In
some use cases, however, the condition for turning a scheme on and off
would depend on the system's situation. For example, schemes for
proactive pages reclamation would need to be turned on when some memory
pressure is detected, and turned off when the system has enough free
memory.
For easier control of schemes activation based on the system situation,
this introduces a watermarks-based mechanism. The client can describe
the watermark metric (e.g., amount of free memory in the system),
watermark check interval, and three watermarks, namely high, mid, and
low. If the scheme is deactivated, it only gets the metric and compare
that to the three watermarks for every check interval. If the metric is
higher than the high watermark, the scheme is deactivated. If the
metric is between the mid watermark and the low watermark, the scheme is
activated. If the metric is lower than the low watermark, the scheme is
deactivated again. This is to allow users fall back to traditional
page-granularity mechanisms.
Link: https://lkml.kernel.org/r/20211019150731.16699-12-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Introduction
============
This patchset 1) makes the engine for general data access
pattern-oriented memory management (DAMOS) be more useful for production
environments, and 2) implements a static kernel module for lightweight
proactive reclamation using the engine.
Proactive Reclamation
---------------------
On general memory over-committed systems, proactively reclaiming cold
pages helps saving memory and reducing latency spikes that incurred by
the direct reclaim or the CPU consumption of kswapd, while incurring
only minimal performance degradation[2].
A Free Pages Reporting[8] based memory over-commit virtualization system
would be one more specific use case. In the system, the guest VMs
reports their free memory to host, and the host reallocates the reported
memory to other guests. As a result, the system's memory utilization
can be maximized. However, the guests could be not so memory-frugal,
because some kernel subsystems and user-space applications are designed
to use as much memory as available. Then, guests would report only
small amount of free memory to host, results in poor memory utilization.
Running the proactive reclamation in such guests could help mitigating
this problem.
Google has also implemented this idea and using it in their data center.
They further proposed upstreaming it in LSFMM'19, and "the general
consensus was that, while this sort of proactive reclaim would be useful
for a number of users, the cost of this particular solution was too high
to consider merging it upstream"[3]. The cost mainly comes from the
coldness tracking. Roughly speaking, the implementation periodically
scans the 'Accessed' bit of each page. For the reason, the overhead
linearly increases as the size of the memory and the scanning frequency
grows. As a result, Google is known to dedicating one CPU for the work.
That's a reasonable option to someone like Google, but it wouldn't be so
to some others.
DAMON and DAMOS: An engine for data access pattern-oriented memory management
-----------------------------------------------------------------------------
DAMON[4] is a framework for general data access monitoring. Its
adaptive monitoring overhead control feature minimizes its monitoring
overhead. It also let the upper-bound of the overhead be configurable
by clients, regardless of the size of the monitoring target memory.
While monitoring 70 GiB memory of a production system every 5
milliseconds, it consumes less than 1% single CPU time. For this, it
could sacrify some of the quality of the monitoring results.
Nevertheless, the lower-bound of the quality is configurable, and it
uses a best-effort algorithm for better quality. Our test results[5]
show the quality is practical enough. From the production system
monitoring, we were able to find a 4 KiB region in the 70 GiB memory
that shows highest access frequency.
We normally don't monitor the data access pattern just for fun but to
improve something like memory management. Proactive reclamation is one
such usage. For such general cases, DAMON provides a feature called
DAMon-based Operation Schemes (DAMOS)[6]. It makes DAMON an engine for
general data access pattern oriented memory management. Using this,
clients can ask DAMON to find memory regions of specific data access
pattern and apply some memory management action (e.g., page out, move to
head of the LRU list, use huge page, ...). We call the request
'scheme'.
Proactive Reclamation on top of DAMON/DAMOS
-------------------------------------------
Therefore, by using DAMON for the cold pages detection, the proactive
reclamation's monitoring overhead issue can be solved. Actually, we
previously implemented a version of proactive reclamation using DAMOS
and achieved noticeable improvements with our evaluation setup[5].
Nevertheless, it more for a proof-of-concept, rather than production
uses. It supports only virtual address spaces of processes, and require
additional tuning efforts for given workloads and the hardware. For the
tuning, we introduced a simple auto-tuning user space tool[8]. Google
is also known to using a ML-based similar approach for their fleets[2].
But, making it just works with intuitive knobs in the kernel would be
helpful for general users.
To this end, this patchset improves DAMOS to be ready for such
production usages, and implements another version of the proactive
reclamation, namely DAMON_RECLAIM, on top of it.
DAMOS Improvements: Aggressiveness Control, Prioritization, and Watermarks
--------------------------------------------------------------------------
First of all, the current version of DAMOS supports only virtual address
spaces. This patchset makes it supports the physical address space for
the page out action.
Next major problem of the current version of DAMOS is the lack of the
aggressiveness control, which can results in arbitrary overhead. For
example, if huge memory regions having the data access pattern of
interest are found, applying the requested action to all of the regions
could incur significant overhead. It can be controlled by tuning the
target data access pattern with manual or automated approaches[2,7].
But, some people would prefer the kernel to just work with only
intuitive tuning or default values.
For such cases, this patchset implements a safeguard, namely time/size
quota. Using this, the clients can specify up to how much time can be
used for applying the action, and/or up to how much memory regions the
action can be applied within a user-specified time duration. A followup
question is, to which memory regions should the action applied within
the limits? We implement a simple regions prioritization mechanism for
each action and make DAMOS to apply the action to high priority regions
first. It also allows clients tune the prioritization mechanism to use
different weights for size, access frequency, and age of memory regions.
This means we could use not only LRU but also LFU or some fancy
algorithms like CAR[9] with lightweight overhead.
Though DAMON is lightweight, someone would want to remove even the cold
pages monitoring overhead when it is unnecessary. Currently, it should
manually turned on and off by clients, but some clients would simply
want to turn it on and off based on some metrics like free memory ratio
or memory fragmentation. For such cases, this patchset implements a
watermarks-based automatic activation feature. It allows the clients
configure the metric of their interest, and three watermarks of the
metric. If the metric is higher than the high watermark or lower than
the low watermark, the scheme is deactivated. If the metric is lower
than the mid watermark but higher than the low watermark, the scheme is
activated.
DAMON-based Reclaim
-------------------
Using the improved version of DAMOS, this patchset implements a static
kernel module called 'damon_reclaim'. It finds memory regions that
didn't accessed for specific time duration and page out. Consuming too
much CPU for the paging out operations, or doing pageout too frequently
can be critical for systems configuring their swap devices with
software-defined in-memory block devices like zram/zswap or total number
of writes limited devices like SSDs, respectively. To avoid the
problems, the time/size quotas can be configured. Under the quotas, it
pages out memory regions that didn't accessed longer first. Also, to
remove the monitoring overhead under peaceful situation, and to fall
back to the LRU-list based page granularity reclamation when it doesn't
make progress, the three watermarks based activation mechanism is used,
with the free memory ratio as the watermark metric.
For convenient configurations, it provides several module parameters.
Using these, sysadmins can enable/disable it, and tune its parameters
including the coldness identification time threshold, the time/size
quotas and the three watermarks.
Evaluation
==========
In short, DAMON_RECLAIM with 50ms/s time quota and regions
prioritization on v5.15-rc5 Linux kernel with ZRAM swap device achieves
38.58% memory saving with only 1.94% runtime overhead. For this,
DAMON_RECLAIM consumes only 4.97% of single CPU time.
Setup
-----
We evaluate DAMON_RECLAIM to show how each of the DAMOS improvements
make effect. For this, we measure DAMON_RECLAIM's CPU consumption,
entire system memory footprint, total number of major page faults, and
runtime of 24 realistic workloads in PARSEC3 and SPLASH-2X benchmark
suites on my QEMU/KVM based virtual machine. The virtual machine runs
on an i3.metal AWS instance, has 130GiB memory, and runs a linux kernel
built on latest -mm tree[1] plus this patchset. It also utilizes a 4
GiB ZRAM swap device. We repeats the measurement 5 times and use
averages.
[1] https://github.com/hnaz/linux-mm/tree/v5.15-rc5-mmots-2021-10-13-19-55
Detailed Results
----------------
The results are summarized in the below table.
With coldness identification threshold of 5 seconds, DAMON_RECLAIM
without the time quota-based speed limit achieves 47.21% memory saving,
but incur 4.59% runtime slowdown to the workloads on average. For this,
DAMON_RECLAIM consumes about 11.28% single CPU time.
Applying time quotas of 200ms/s, 50ms/s, and 10ms/s without the regions
prioritization reduces the slowdown to 4.89%, 2.65%, and 1.5%,
respectively. Time quota of 200ms/s (20%) makes no real change compared
to the quota unapplied version, because the quota unapplied version
consumes only 11.28% CPU time. DAMON_RECLAIM's CPU utilization also
similarly reduced: 11.24%, 5.51%, and 2.01% of single CPU time. That
is, the overhead is proportional to the speed limit. Nevertheless, it
also reduces the memory saving because it becomes less aggressive. In
detail, the three variants show 48.76%, 37.83%, and 7.85% memory saving,
respectively.
Applying the regions prioritization (page out regions that not accessed
longer first within the time quota) further reduces the performance
degradation. Runtime slowdowns and total number of major page faults
increase has been 4.89%/218,690% -> 4.39%/166,136% (200ms/s),
2.65%/111,886% -> 1.94%/59,053% (50ms/s), and 1.5%/34,973.40% ->
2.08%/8,781.75% (10ms/s). The runtime under 10ms/s time quota has
increased with prioritization, but apparently that's under the margin of
error.
time quota prioritization memory_saving cpu_util slowdown pgmajfaults overhead
N N 47.21% 11.28% 4.59% 194,802%
200ms/s N 48.76% 11.24% 4.89% 218,690%
50ms/s N 37.83% 5.51% 2.65% 111,886%
10ms/s N 7.85% 2.01% 1.5% 34,793.40%
200ms/s Y 50.08% 10.38% 4.39% 166,136%
50ms/s Y 38.58% 4.97% 1.94% 59,053%
10ms/s Y 3.63% 1.73% 2.08% 8,781.75%
Baseline and Complete Git Trees
===============================
The patches are based on the latest -mm tree
(v5.15-rc5-mmots-2021-10-13-19-55). You can also clone the complete git tree
from:
$ git clone git://github.com/sjp38/linux -b damon_reclaim/patches/v1
The web is also available:
https://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git/tag/?h=damon_reclaim/patches/v1
Sequence Of Patches
===================
The first patch makes DAMOS support the physical address space for the
page out action. Following five patches (patches 2-6) implement the
time/size quotas. Next four patches (patches 7-10) implement the memory
regions prioritization within the limit. Then, three following patches
(patches 11-13) implement the watermarks-based schemes activation.
Finally, the last two patches (patches 14-15) implement and document the
DAMON-based reclamation using the advanced DAMOS.
[1] https://www.kernel.org/doc/html/v5.15-rc1/vm/damon/index.html
[2] https://research.google/pubs/pub48551/
[3] https://lwn.net/Articles/787611/
[4] https://damonitor.github.io
[5] https://damonitor.github.io/doc/html/latest/vm/damon/eval.html
[6] https://lore.kernel.org/linux-mm/20211001125604.29660-1-sj@kernel.org/
[7] https://github.com/awslabs/damoos
[8] https://www.kernel.org/doc/html/latest/vm/free_page_reporting.html
[9] https://www.usenix.org/conference/fast-04/car-clock-adaptive-replacement
This patch (of 15):
This makes the DAMON primitives for physical address space support the
pageout action for DAMON-based Operation Schemes. With this commit,
hence, users can easily implement system-level data access-aware
reclamations using DAMOS.
[sj@kernel.org: fix missing-prototype build warning]
Link: https://lkml.kernel.org/r/20211025064220.13904-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211019150731.16699-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211019150731.16699-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Marco Elver <elver@google.com>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Greg Thelen <gthelen@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
