On Thu, Apr 8, 2021 at 7:31 AM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > When the unsigned page_counter underflows, even just by a few pages, a > cgroup will not be able to run anything afterwards and trigger the OOM > killer in a loop. > > Underflows shouldn't happen, but when they do in practice, we may just > be off by a small amount that doesn't interfere with the normal > operation - consequences don't need to be that dire. > > Reset the page_counter to 0 upon underflow. We'll issue a warning that > the accounting will be off and then try to keep limping along. > > [ We used to do this with the original res_counter, where it was a > more straight-forward correction inside the spinlock section. I > didn't carry it forward into the lockless page counters for > simplicity, but it turns out this is quite useful in practice. ] > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
