I believe the patch should be accepted. While the race condition might be rare in simple workloads, it can become significant in containerized systems or Android devices. The proposed solution is simple, low-risk, and directly addresses the identified problem with minimal code changes.

On August 15, 2025 3:09:14 AM GMT+04:00, Andrew Morton <akpm@linux-foundation.org> wrote:

On Thu, 14 Aug 2025 21:55:55 +0800 <zhongjinji@honor.com> wrote:

When a process is OOM killed, if the OOM reaper and the thread running
exit_mmap() execute at the same time, both will traverse the vma's maple
tree along the same path. They may easily unmap the same vma, causing them
to compete for the pte spinlock. This increases unnecessary load, causing
the execution time of the OOM reaper and the thread running exit_mmap() to
increase.

Please tell me what I'm missing here.

OOM kills are a rare event.  And this race sounds like it will rarely
occur even if an oom-killing is happening.  And the delay will be
relatively short.

If I'm correct then we're addressing rare*rare*small, so why bother?

When a process exits, exit_mmap() traverses the vma's maple tree from low to high
address. To reduce the chance of unmapping the same vma simultaneously,
the OOM reaper should traverse vma's tree from high to low address. This reduces
lock contention when unmapping the same vma.

Sharing some before-and-after runtime measurements would be useful.  Or
at least, detailed anecdotes.