linux-kernel - Re: [PATCH 3/3] memcg: reduce size of memcg vmstats structures

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Yxko0AxuVO6oiN5M@P9FQF9L96D.corp.robot.car>
Date:   Wed, 7 Sep 2022 16:27:12 -0700
From:   Roman Gushchin <roman.gushchin@...ux.dev>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] memcg: reduce size of memcg vmstats structures

On Wed, Sep 07, 2022 at 04:35:37AM +0000, Shakeel Butt wrote:
> The struct memcg_vmstats and struct memcg_vmstats_percpu contains two
> arrays each for events of size NR_VM_EVENT_ITEMS which can be as large
> as 110. However the memcg v1 only uses 4 of those while memcg v2 uses
> 15. The union of both is 17. On a 64 bit system, we are wasting
> approximately ((110 - 17) * 8 * 2) * (nr_cpus + 1) bytes which is
> significant on large machines.
> 
> This patch reduces the size of the given structures by adding one
> indirection and only stores array of events which are actually used by
> the memcg code. With this patch, the size of memcg_vmstats has reduced
> from 2544 bytes to 1056 bytes while the size of memcg_vmstats_percpu has
> reduced from 2568 bytes to 1080 bytes.

This is pretty impressive!

Thank you, Shakeel!

Acked-by: Roman Gushchin <roman.gushchin@...ux.dev>
for the series.

Thanks!