linux-kernel - Re: [PATCH] mm: fadvise: avoid expensive remote LRU cache draining after FADV

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 for Android: free password hash cracker in your pocket

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

Date:   Mon, 12 Dec 2016 09:51:24 +0000
From:   Mel Gorman <mgorman@...e.de>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH] mm: fadvise: avoid expensive remote LRU cache draining
 after FADV_DONTNEED

On Sat, Dec 10, 2016 at 12:26:58PM -0500, Johannes Weiner wrote:
> When FADV_DONTNEED cannot drop all pages in the range, it observes
> that some pages might still be on per-cpu LRU caches after recent
> instantiation and so initiates remote calls to all CPUs to flush their
> local caches. However, in most cases, the fadvise happens from the
> same context that instantiated the pages, and any pre-LRU pages in the
> specified range are most likely sitting on the local CPU's LRU cache,
> and so in many cases this results in unnecessary remote calls, which,
> in a loaded system, can hold up the fadvise() call significantly.
> 
> Try to avoid the remote call by flushing the local LRU cache before
> even attempting to invalidate anything. It's a cheap operation, and
> the local LRU cache is the most likely to hold any pre-LRU pages in
> the specified fadvise range.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs