From: Roman Gushchin <guro@fb.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Michal Hocko <mhocko@suse.com>,
<linux-mm@kvack.org>, <cgroups@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <kernel-team@fb.com>
Subject: Re: [PATCH 1/7] mm: memcontrol: fix cpuhotplug statistics flushing
Date: Tue, 2 Feb 2021 15:07:47 -0800 [thread overview]
Message-ID: <20210202230747.GA1812008@carbon.dhcp.thefacebook.com> (raw)
In-Reply-To: <20210202184746.119084-2-hannes@cmpxchg.org>
On Tue, Feb 02, 2021 at 01:47:40PM -0500, Johannes Weiner wrote:
> The memcg hotunplug callback erroneously flushes counts on the local
> CPU, not the counts of the CPU going away; those counts will be lost.
>
> Flush the CPU that is actually going away.
>
> Also simplify the code a bit by using mod_memcg_state() and
> count_memcg_events() instead of open-coding the upward flush - this is
> comparable to how vmstat.c handles hotunplug flushing.
To the whole series: it's really nice to have an accurate stats at
non-leaf levels. Just as an illustration: if there are 32 CPUs and
1000 sub-cgroups (which is an absolutely realistic number, because
often there are many dying generations of each cgroup), the error
margin is 3.9GB. It makes all numbers pretty much random and all
possible tests extremely flaky.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
To this patch:
Reviewed-by: Roman Gushchin <guro@fb.com>
Thanks!
WARNING: multiple messages have this Message-ID (diff)
From: Roman Gushchin <guro@fb.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Michal Hocko <mhocko@suse.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 1/7] mm: memcontrol: fix cpuhotplug statistics flushing
Date: Tue, 2 Feb 2021 15:07:47 -0800 [thread overview]
Message-ID: <20210202230747.GA1812008@carbon.dhcp.thefacebook.com> (raw)
In-Reply-To: <20210202184746.119084-2-hannes@cmpxchg.org>
On Tue, Feb 02, 2021 at 01:47:40PM -0500, Johannes Weiner wrote:
> The memcg hotunplug callback erroneously flushes counts on the local
> CPU, not the counts of the CPU going away; those counts will be lost.
>
> Flush the CPU that is actually going away.
>
> Also simplify the code a bit by using mod_memcg_state() and
> count_memcg_events() instead of open-coding the upward flush - this is
> comparable to how vmstat.c handles hotunplug flushing.
To the whole series: it's really nice to have an accurate stats at
non-leaf levels. Just as an illustration: if there are 32 CPUs and
1000 sub-cgroups (which is an absolutely realistic number, because
often there are many dying generations of each cgroup), the error
margin is 3.9GB. It makes all numbers pretty much random and all
possible tests extremely flaky.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
To this patch:
Reviewed-by: Roman Gushchin <guro@fb.com>
Thanks!
next prev parent reply other threads:[~2021-02-02 23:09 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-02 18:47 [PATCH 0/7]: mm: memcontrol: switch to rstat Johannes Weiner
2021-02-02 18:47 ` Johannes Weiner
2021-02-02 18:47 ` [PATCH 1/7] mm: memcontrol: fix cpuhotplug statistics flushing Johannes Weiner
2021-02-02 18:47 ` Johannes Weiner
2021-02-02 22:23 ` Shakeel Butt
2021-02-02 22:23 ` Shakeel Butt
2021-02-02 22:23 ` Shakeel Butt
2021-02-02 23:07 ` Roman Gushchin [this message]
2021-02-02 23:07 ` Roman Gushchin
2021-02-03 2:28 ` Roman Gushchin
2021-02-03 2:28 ` Roman Gushchin
2021-02-04 19:29 ` Johannes Weiner
2021-02-04 19:29 ` Johannes Weiner
2021-02-04 19:34 ` Roman Gushchin
2021-02-04 19:34 ` Roman Gushchin
2021-02-05 17:50 ` Johannes Weiner
2021-02-05 17:50 ` Johannes Weiner
2021-02-04 13:28 ` Michal Hocko
2021-02-04 13:28 ` Michal Hocko
2021-02-02 18:47 ` [PATCH 2/7] mm: memcontrol: kill mem_cgroup_nodeinfo() Johannes Weiner
2021-02-02 18:47 ` Johannes Weiner
2021-02-02 22:24 ` Shakeel Butt
2021-02-02 22:24 ` Shakeel Butt
2021-02-02 22:24 ` Shakeel Butt
2021-02-02 23:13 ` Roman Gushchin
2021-02-02 23:13 ` Roman Gushchin
2021-02-04 13:29 ` Michal Hocko
2021-02-04 13:29 ` Michal Hocko
2021-02-02 18:47 ` [PATCH 3/7] mm: memcontrol: privatize memcg_page_state query functions Johannes Weiner
2021-02-02 18:47 ` Johannes Weiner
2021-02-02 22:26 ` Shakeel Butt
2021-02-02 22:26 ` Shakeel Butt
2021-02-02 23:17 ` Roman Gushchin
2021-02-02 23:17 ` Roman Gushchin
2021-02-04 13:30 ` Michal Hocko
2021-02-04 13:30 ` Michal Hocko
2021-02-02 18:47 ` [PATCH 4/7] cgroup: rstat: support cgroup1 Johannes Weiner
2021-02-02 18:47 ` Johannes Weiner
2021-02-03 1:16 ` Roman Gushchin
2021-02-03 1:16 ` Roman Gushchin
2021-02-04 13:39 ` Michal Hocko
2021-02-04 13:39 ` Michal Hocko
2021-02-04 16:01 ` Johannes Weiner
2021-02-04 16:01 ` Johannes Weiner
2021-02-04 16:42 ` Michal Hocko
2021-02-04 16:42 ` Michal Hocko
2021-02-02 18:47 ` [PATCH 5/7] cgroup: rstat: punt root-level optimization to individual controllers Johannes Weiner
2021-02-02 18:47 ` Johannes Weiner
2021-02-02 18:47 ` [PATCH 6/7] mm: memcontrol: switch to rstat Johannes Weiner
2021-02-02 18:47 ` Johannes Weiner
2021-02-03 1:47 ` Roman Gushchin
2021-02-03 1:47 ` Roman Gushchin
2021-02-04 16:26 ` Johannes Weiner
2021-02-04 16:26 ` Johannes Weiner
2021-02-04 18:45 ` Roman Gushchin
2021-02-04 18:45 ` Roman Gushchin
2021-02-04 20:05 ` Johannes Weiner
2021-02-04 20:05 ` Johannes Weiner
2021-02-04 14:19 ` Michal Hocko
2021-02-04 14:19 ` Michal Hocko
2021-02-04 16:15 ` Johannes Weiner
2021-02-04 16:44 ` Michal Hocko
2021-02-04 16:44 ` Michal Hocko
2021-02-04 20:28 ` Johannes Weiner
2021-02-04 20:28 ` Johannes Weiner
2021-02-05 15:05 ` Michal Hocko
2021-02-05 15:05 ` Michal Hocko
2021-02-05 16:34 ` Johannes Weiner
2021-02-05 16:34 ` Johannes Weiner
2021-02-08 14:07 ` Michal Hocko
2021-02-08 14:07 ` Michal Hocko
2021-02-02 18:47 ` [PATCH 7/7] mm: memcontrol: consolidate lruvec stat flushing Johannes Weiner
2021-02-03 2:25 ` Roman Gushchin
2021-02-03 2:25 ` Roman Gushchin
2021-02-04 21:44 ` Johannes Weiner
2021-02-04 21:44 ` Johannes Weiner
2021-02-04 21:47 ` Roman Gushchin
2021-02-04 21:47 ` Roman Gushchin
2021-02-05 15:17 ` Michal Hocko
2021-02-05 15:17 ` Michal Hocko
2021-02-05 17:10 ` Johannes Weiner
2021-02-05 17:10 ` Johannes Weiner
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