linux-kernel - Re: [RFC PATCH] mm, thp: make deferred_split

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: <20171020071250.ftqn2d356yekkp5k@dhcp22.suse.cz>
Date:   Fri, 20 Oct 2017 09:12:50 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Neha Agarwal <nehaagarwal@...gle.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Rientjes <rientjes@...gle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Kemi Wang <kemi.wang@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Shaohua Li <shli@...com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, cgroups@...r.kernel.org
Subject: Re: [RFC PATCH] mm, thp: make deferred_split_shrinker memcg-aware

On Thu 19-10-17 13:03:23, Neha Agarwal wrote:
> deferred_split_shrinker is NUMA aware. Making it memcg-aware if
> CONFIG_MEMCG is enabled to prevent shrinking memory of memcg(s) that are
> not under memory pressure. This change isolates memory pressure across
> memcgs from deferred_split_shrinker perspective, by not prematurely
> splitting huge pages for the memcg that is not under memory pressure.

Why do we need this? THP pages are usually not shared between memcgs. Or
do you have a real world example where this is not the case? Your patch
is adding quite a lot of (and to be really honest very ugly) code so
there better should be a _very_ good reason to justify it. I haven't
looked very closely to the code, at least all those ifdefs in the code
are too ugly to live.
-- 
Michal Hocko
SUSE Labs