linux-kernel - Re: [PATCH 4/4] mm/memcg: refine mem_cgroup_threshold_ary->current

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: <Yd3LLalWzPy17PmR@carbon.dhcp.thefacebook.com>
Date:   Tue, 11 Jan 2022 10:23:41 -0800
From:   Roman Gushchin <guro@...com>
To:     Wei Yang <richard.weiyang@...il.com>
CC:     <hannes@...xchg.org>, <mhocko@...nel.org>,
        <vdavydov.dev@...il.com>, <akpm@...ux-foundation.org>,
        <shakeelb@...gle.com>, <vbabka@...e.cz>, <willy@...radead.org>,
        <songmuchun@...edance.com>, <shy828301@...il.com>,
        <surenb@...gle.com>, <linux-kernel@...r.kernel.org>,
        <cgroups@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH 4/4] mm/memcg: refine
 mem_cgroup_threshold_ary->current_threshold calculation

On Tue, Jan 11, 2022 at 01:03:02AM +0000, Wei Yang wrote:
> mem_cgroup_threshold_ary->current_threshold points to the last entry
> who's threshold is less or equal to usage.
> 
> Instead of iterating entries to get the correct index, we can leverage
> primary->current_threshold to get it. If the threshold added is less or
> equal to usage, current_threshold should increase by one. Otherwise, it
> doesn't change.

How big is usually an array of thresholds? If it's not huge, likely
any savings won't be really noticeable (it's not a hot path and there
is an rc_synchronize() below).

So I agree with Michal that a better justification is really needed.

Thanks!