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perf/core: Rework memory accounting in perf_mmap()

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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 <[email protected]>
Reported-by: Hechao Li <[email protected]>
Signed-off-by: Song Liu <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: <[email protected]>
Cc: Jie Meng <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Song Liu authored and Ingo Molnar committed 2019-10-09 12:44:12 +02:00
1 parent f733c6b508
commit d44248a413
1 file changed
+15 -2
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kernel/events/core.c
+15 -2
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@@ -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;