linux-kernel - Re: [PATCH] Reduce vm_stat cacheline contention in __vm_enough

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: <20111013135032.7c2c54cd.akpm@linux-foundation.org>
Date:	Thu, 13 Oct 2011 13:50:32 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Christoph Lameter <cl@...two.org>
Cc:	Dimitri Sivanich <sivanich@....com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH] Reduce vm_stat cacheline contention in
 __vm_enough_memory

On Thu, 13 Oct 2011 10:54:30 -0500 (CDT)
Christoph Lameter <cl@...two.org> wrote:

> On Thu, 13 Oct 2011, Dimitri Sivanich wrote:
> 
> > > increase the allowed delta per zone if frequent updates occur via the
> > > overflow checks in vmstat.c. See calculate_*_threshold there.
> >
> > I tried changing the threshold in both directions, with slower throughput in
> > both cases.
> 
> If that is the case check for the vm_stat cacheline being shared with
> another hot kernel variable variable. Maybe that causes cacheline
> eviction.

yup.  `nm -n vmlinux'.

> If there are no updates occurring for a while (due to increased deltas
> and/or vmstat updates) then the vm_stat cacheline should be able to stay
> in shared mode in multiple processors and the performance should increase.
> 

We could cacheline align vm_stat[].  But the thing is pretty small - we
couild put each entry in its own cacheline.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/