summaryrefslogtreecommitdiff
path: root/mm/mmap.c
diff options
context:
space:
mode:
authorSuren Baghdasaryan <surenb@google.com>2022-06-01 01:30:59 +0300
committerAndrew Morton <akpm@linux-foundation.org>2022-09-27 05:46:27 +0300
commitbf3980c85212fc71512d27a46f5aab66f46ca284 (patch)
treecb7ceb429fc3cfa774209cf6fbdda40d292ff2a6 /mm/mmap.c
parent66071896cdfe096fcd4aef55a5efbd5216fa15de (diff)
downloadlinux-bf3980c85212fc71512d27a46f5aab66f46ca284.tar.xz
mm: drop oom code from exit_mmap
The primary reason to invoke the oom reaper from the exit_mmap path used to be a prevention of an excessive oom killing if the oom victim exit races with the oom reaper (see [1] for more details). The invocation has moved around since then because of the interaction with the munlock logic but the underlying reason has remained the same (see [2]). Munlock code is no longer a problem since [3] and there shouldn't be any blocking operation before the memory is unmapped by exit_mmap so the oom reaper invocation can be dropped. The unmapping part can be done with the non-exclusive mmap_sem and the exclusive one is only required when page tables are freed. Remove the oom_reaper from exit_mmap which will make the code easier to read. This is really unlikely to make any observable difference although some microbenchmarks could benefit from one less branch that needs to be evaluated even though it almost never is true. [1] 212925802454 ("mm: oom: let oom_reap_task and exit_mmap run concurrently") [2] 27ae357fa82b ("mm, oom: fix concurrent munlock and oom reaper unmap, v3") [3] a213e5cf71cb ("mm/munlock: delete munlock_vma_pages_all(), allow oomreap") [akpm@linux-foundation.org: restore Suren's mmap_read_lock() optimization] Link: https://lkml.kernel.org/r/20220531223100.510392-1-surenb@google.com Signed-off-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Brauner (Microsoft) <brauner@kernel.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Jann Horn <jannh@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: John Hubbard <jhubbard@nvidia.com> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Xu <peterx@redhat.com> Cc: Roman Gushchin <guro@fb.com> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c30
1 files changed, 11 insertions, 19 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index fbe8b52a90a3..be111bbe8075 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3085,30 +3085,13 @@ void exit_mmap(struct mm_struct *mm)
/* mm's last user has gone, and its about to be pulled down */
mmu_notifier_release(mm);
- if (unlikely(mm_is_oom_victim(mm))) {
- /*
- * Manually reap the mm to free as much memory as possible.
- * Then, as the oom reaper does, set MMF_OOM_SKIP to disregard
- * this mm from further consideration. Taking mm->mmap_lock for
- * write after setting MMF_OOM_SKIP will guarantee that the oom
- * reaper will not run on this mm again after mmap_lock is
- * dropped.
- *
- * Nothing can be holding mm->mmap_lock here and the above call
- * to mmu_notifier_release(mm) ensures mmu notifier callbacks in
- * __oom_reap_task_mm() will not block.
- */
- (void)__oom_reap_task_mm(mm);
- set_bit(MMF_OOM_SKIP, &mm->flags);
- }
-
- mmap_write_lock(mm);
+ mmap_read_lock(mm);
arch_exit_mmap(mm);
vma = mas_find(&mas, ULONG_MAX);
if (!vma) {
/* Can happen if dup_mmap() received an OOM */
- mmap_write_unlock(mm);
+ mmap_read_unlock(mm);
return;
}
@@ -3118,6 +3101,15 @@ void exit_mmap(struct mm_struct *mm)
/* update_hiwater_rss(mm) here? but nobody should be looking */
/* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */
unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX);
+ mmap_read_unlock(mm);
+
+ /*
+ * Set MMF_OOM_SKIP to hide this task from the oom killer/reaper
+ * because the memory has been already freed. Do not bother checking
+ * mm_is_oom_victim because setting a bit unconditionally is cheaper.
+ */
+ set_bit(MMF_OOM_SKIP, &mm->flags);
+ mmap_write_lock(mm);
free_pgtables(&tlb, &mm->mm_mt, vma, FIRST_USER_ADDRESS,
USER_PGTABLES_CEILING);
tlb_finish_mmu(&tlb);