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Subject[patch v2 2/2] mm, oom: avoid reaping only for mm's with blockable invalidate callbacks
This uses the new annotation to determine if an mm has mmu notifiers with
blockable invalidate range callbacks to avoid oom reaping. Otherwise, the
callbacks are used around unmap_page_range().

Signed-off-by: David Rientjes <rientjes@google.com>
---
mm/oom_kill.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -514,15 +514,12 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
}

/*
- * If the mm has notifiers then we would need to invalidate them around
- * unmap_page_range and that is risky because notifiers can sleep and
- * what they do is basically undeterministic. So let's have a short
+ * If the mm has invalidate_{start,end}() notifiers that could block,
* sleep to give the oom victim some more time.
* TODO: we really want to get rid of this ugly hack and make sure that
- * notifiers cannot block for unbounded amount of time and add
- * mmu_notifier_invalidate_range_{start,end} around unmap_page_range
+ * notifiers cannot block for unbounded amount of time
*/
- if (mm_has_notifiers(mm)) {
+ if (mm_has_blockable_invalidate_notifiers(mm)) {
up_read(&mm->mmap_sem);
schedule_timeout_idle(HZ);
goto unlock_oom;
@@ -565,10 +562,14 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
* count elevated without a good reason.
*/
if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
- tlb_gather_mmu(&tlb, mm, vma->vm_start, vma->vm_end);
- unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
- NULL);
- tlb_finish_mmu(&tlb, vma->vm_start, vma->vm_end);
+ const unsigned long start = vma->vm_start;
+ const unsigned long end = vma->vm_end;
+
+ tlb_gather_mmu(&tlb, mm, start, end);
+ mmu_notifier_invalidate_range_start(mm, start, end);
+ unmap_page_range(&tlb, vma, start, end, NULL);
+ mmu_notifier_invalidate_range_end(mm, start, end);
+ tlb_finish_mmu(&tlb, start, end);
}
}
pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
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