On Mon, Apr 14, 2025 at 03:55:39PM +0200, Michal Koutný wrote:
On Mon, Apr 14, 2025 at 09:15:57AM -0400, Waiman Long llong@redhat.com wrote:
I did see some low event in the no usage case because of the ">=" comparison used in mem_cgroup_below_min().
Do you refer to A/B/E or A/B/F from the test? It's OK to see some events if there was non-zero usage initially.
Nevertheless, which situation this patch changes that is not handled by mem_cgroup_below_min() already?
It's not a functional change to the protection semantics or the reclaim behavior.
The problem is if we go into low_reclaim and encounter an empty group, we'll issue "low-protected group is being reclaimed" events, which is kind of absurd (nothing will be reclaimed) and thus confusing to users (I didn't even configure any protection!)
I suggested, instead of redefining the protection definitions for that special case, to bypass all the checks and the scan count calculations when we already know the group is empty and none of this applies.
https://lore.kernel.org/linux-mm/20250404181308.GA300138@cmpxchg.org/