Re: [PATCH 3/3] mm: Fix missing mem cgroup soft limit tree updates
From: Johannes Weiner <hidden>
Date: 2021-02-10 01:13:10
Also in:
linux-mm, lkml
Hello Tim, On Tue, Feb 09, 2021 at 12:29:47PM -0800, Tim Chen wrote:
quoted hunk ↗ jump to hunk
@@ -6849,7 +6850,9 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug) * exclusive access to the page. */ - if (ug->memcg != page_memcg(page)) { + if (ug->memcg != page_memcg(page) || + /* uncharge batch update soft limit tree on a node basis */ + (ug->dummy_page && ug->nid != page_to_nid(page))) {
The fix makes sense to me. However, unconditionally breaking up the batch by node can unnecessarily regress workloads in cgroups that do not have a soft limit configured, and cgroup2 which doesn't have soft limits at all. Consider an interleaving allocation policy for example. Can you please further gate on memcg->soft_limit != PAGE_COUNTER_MAX, or at least on !cgroup_subsys_on_dfl(memory_cgrp_subsys)? Thanks