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mm/thp: check and bail out if page in deferred queue already

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Kernel build regression with LLVM was reported here:
https://lore.kernel.org/all/Y1GCYXGtEVZbcv%2F5@dev-arch.thelio-3990X/ with
commit f35b5d7d67 ("mm: align larger anonymous mappings on THP
boundaries").  And the commit f35b5d7d67 was reverted.

It turned out the regression is related with madvise(MADV_DONTNEED)
was used by ld.lld. But with none PMD_SIZE aligned parameter len.
trace-bpfcc captured:
531607  531732  ld.lld          do_madvise.part.0 start: 0x7feca9000000, len: 0x7fb000, behavior: 0x4
531607  531793  ld.lld          do_madvise.part.0 start: 0x7fec86a00000, len: 0x7fb000, behavior: 0x4

If the underneath physical page is THP, the madvise(MADV_DONTNEED) can
trigger split_queue_lock contention raised significantly. perf showed
following data:
    14.85%     0.00%  ld.lld           [kernel.kallsyms]           [k]
       entry_SYSCALL_64_after_hwframe
           11.52%
                entry_SYSCALL_64_after_hwframe
                do_syscall_64
                __x64_sys_madvise
                do_madvise.part.0
                zap_page_range
                unmap_single_vma
                unmap_page_range
                page_remove_rmap
                deferred_split_huge_page
                __lock_text_start
                native_queued_spin_lock_slowpath

If THP can't be removed from rmap as whole THP, partial THP will be
removed from rmap by removing sub-pages from rmap.  Even the THP head page
is added to deferred queue already, the split_queue_lock will be acquired
and check whether the THP head page is in the queue already.  Thus, the
contention of split_queue_lock is raised.

Before acquire split_queue_lock, check and bail out early if the THP
head page is in the queue already. The checking without holding
split_queue_lock could race with deferred_split_scan, but it doesn't
impact the correctness here.

Test result of building kernel with ld.lld:
commit 7b5a0b664e (parent commit of f35b5d7d67):
time -f "\t%E real,\t%U user,\t%S sys" make LD=ld.lld -skj96 allmodconfig all
        6:07.99 real,   26367.77 user,  5063.35 sys

commit f35b5d7d67:
time -f "\t%E real,\t%U user,\t%S sys" make LD=ld.lld -skj96 allmodconfig all
        7:22.15 real,   26235.03 user,  12504.55 sys

commit f35b5d7d67 with the fixing patch:
time -f "\t%E real,\t%U user,\t%S sys" make LD=ld.lld -skj96 allmodconfig all
        6:08.49 real,   26520.15 user,  5047.91 sys

Link: https://lkml.kernel.org/r/20221223135207.2275317-1-fengwei.yin@intel.com
Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Yin Fengwei 2022-12-23 21:52:07 +08:00 committed by Andrew Morton
parent 01b5022f0a
commit 81e506bec9
1 changed files with 3 additions and 0 deletions
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3
mm/huge_memory.c
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@ -2835,6 +2835,9 @@ void deferred_split_huge_page(struct page *page)
if (PageSwapCache(page))
return;
if (!list_empty(page_deferred_list(page)))
return;
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
if (list_empty(page_deferred_list(page))) {
count_vm_event(THP_DEFERRED_SPLIT_PAGE);