On Wed, May 11, 2022 at 01:53:05PM -0400, Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > Can you indeed elaborate on the problem you see with low events? My mistake. I realized I was testing on a system without memory_recursiveprot enabled. Therefore I saw no events in children with memory.low=0. However, it also means that my previous evaluation of the "simple" fix (dropping the SWAP_CLUSTER_MAX rounding) was incorrect and it actually doesn't resolve the problem of two differently active siblings I posted earlier. > So your proposed patch looks like the right thing to do to me. And I > would ack it, but please do explain your concerns around low event > reporting after it. I retract it (at least for now), it doesn't really help. It can be seen (after application) [1] that once (low) protected memory is opened for reclaim, the sibling proportions change suddenly (neither sibling is protected during sc->memcg_low_reclaim, however, the formerly protected suddenly provides good supply of reclaimable pages). OTOH, without memory_recursiveprot [2], the elow growth of the victim sibling is absent and situation stabilizes with only partial reclaim from the (explicitly) protected sibling. In both variants (recursive/non-recursive) the parent ends up with same amount of unreclaimed memory, however, the gradual tranfer of elow with the recursive protection is undesired. (I'm only thinking how to solve it simply.) Michal [1] https://bugzilla.suse.com/attachment.cgi?id=858869 [2] https://bugzilla.suse.com/attachment.cgi?id=858870
