From d44248a41337731a111374822d7d4451b64e73e4 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Wed, 4 Sep 2019 14:46:18 -0700 Subject: perf/core: Rework memory accounting in perf_mmap() perf_mmap() always increases user->locked_vm. As a result, "extra" could grow bigger than "user_extra", which doesn't make sense. Here is an example case: (Note: Assume "user_lock_limit" is very small.) | # of perf_mmap calls |vma->vm_mm->pinned_vm|user->locked_vm| | 0 | 0 | 0 | | 1 | user_extra | user_extra | | 2 | 3 * user_extra | 2 * user_extra| | 3 | 6 * user_extra | 3 * user_extra| | 4 | 10 * user_extra | 4 * user_extra| Fix this by maintaining proper user_extra and extra. Reviewed-By: Hechao Li Reported-by: Hechao Li Signed-off-by: Song Liu Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Jie Meng Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20190904214618.3795672-1-songliubraving@fb.com Signed-off-by: Ingo Molnar --- kernel/events/core.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/events/core.c b/kernel/events/core.c index f953dd16a5e2..2b8265ad7bf5 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5668,7 +5668,8 @@ again: * undo the VM accounting. */ - atomic_long_sub((size >> PAGE_SHIFT) + 1, &mmap_user->locked_vm); + atomic_long_sub((size >> PAGE_SHIFT) + 1 - mmap_locked, + &mmap_user->locked_vm); atomic64_sub(mmap_locked, &vma->vm_mm->pinned_vm); free_uid(mmap_user); @@ -5812,8 +5813,20 @@ accounting: user_locked = atomic_long_read(&user->locked_vm) + user_extra; - if (user_locked > user_lock_limit) + if (user_locked <= user_lock_limit) { + /* charge all to locked_vm */ + } else if (atomic_long_read(&user->locked_vm) >= user_lock_limit) { + /* charge all to pinned_vm */ + extra = user_extra; + user_extra = 0; + } else { + /* + * charge locked_vm until it hits user_lock_limit; + * charge the rest from pinned_vm + */ extra = user_locked - user_lock_limit; + user_extra -= extra; + } lock_limit = rlimit(RLIMIT_MEMLOCK); lock_limit >>= PAGE_SHIFT; -- cgit v1.2.3