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Date: Fri, 22 Mar 2019 22:49:46 +0000 From: Chris Down <chris@...isdown.name> To: Roman Gushchin <guro@...com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, Tejun Heo <tj@...nel.org>, Dennis Zhou <dennis@...nel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, Kernel Team <Kernel-team@...com> Subject: Re: [PATCH REBASED] mm, memcg: Make scan aggression always exclude protection Roman Gushchin writes: >I've noticed that the old version is just wrong: if cgroup_size is way smaller >than max(min, low), scan will be set to -lruvec_size. >Given that it's unsigned long, we'll end up with scanning the whole list >(due to clamp() below). Are you certain? If so, I don't see what you mean. This is how the code looks in Linus' tree after the fixups: unsigned long cgroup_size = mem_cgroup_size(memcg); unsigned long baseline = 0; if (!sc->memcg_low_reclaim) baseline = lruvec_size; scan = lruvec_size * cgroup_size / protection - baseline; This works correctly as far as I can tell: low reclaim case: In [1]: cgroup_size=50; lruvec_size=10; protection=2000; baseline=0; lruvec_size * cgroup_size // protection - baseline Out[1]: 0 normal case: In [2]: cgroup_size=3000; lruvec_size=10; protection=2000; baseline=lruvec_size; lruvec_size * cgroup_size // protection - baseline Out[2]: 5
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