From: David Rientjes <rientjes@google.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Dimitri Sivanich <sivanich@sgi.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Christoph Lameter <cl@gentwo.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mel@csn.ul.ie>
Subject: Re: [PATCH] Reduce vm_stat cacheline contention in __vm_enough_memory
Date: Tue, 18 Oct 2011 18:16:21 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1110181806570.12850@chino.kir.corp.google.com> (raw)
In-Reply-To: <m2mxcyz4f7.fsf@firstfloor.org>
On Tue, 18 Oct 2011, Andi Kleen wrote:
> > Would it make sense to have the ZVC delta be tuneable (via /proc/sys/vm?), keeping the
> > same default behavior as what we currently have?
>
> Tunable is bad. We don't really want a "hundreds of lines magic shell script to
> make large systems perform". Please find a way to auto tune.
>
Agreed, and I think even if we had a tunable that it would result in
potentially erradic VM performance because some areas depend on "fairly
accurate" ZVCs and it wouldn't be clear that you're trading other unknown
VM issues that will affect your workload because you've increased the
deltas. Let's try to avoid having to ask "what is your ZVC delta tunable
set at?" when someone reports a bug about reclaim stopping preemptively.
That said, perhaps we need higher deltas by default and then hints in key
areas in the form of sync_stats_if_delta_above(x) calls that would do
zone_page_state_add() only when that kind of precision is actually needed.
For public interfaces, that would be very easy to audit to see what the
level of precision is when parsing the data.
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next prev parent reply other threads:[~2011-10-19 1:16 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20111012160202.GA18666@sgi.com>
2011-10-12 19:01 ` Andrew Morton
2011-10-12 19:57 ` Christoph Lameter
2011-10-13 15:06 ` Mel Gorman
2011-10-13 15:59 ` Andi Kleen
2011-10-13 15:23 ` Dimitri Sivanich
2011-10-13 15:54 ` Christoph Lameter
2011-10-13 20:50 ` Andrew Morton
2011-10-13 21:02 ` Christoph Lameter
2011-10-13 21:24 ` Andrew Morton
2011-10-14 12:25 ` Dimitri Sivanich
2011-10-14 13:50 ` Dimitri Sivanich
2011-10-14 13:57 ` Christoph Lameter
2011-10-14 14:19 ` Dimitri Sivanich
2011-10-14 14:34 ` Christoph Lameter
2011-10-14 15:18 ` Christoph Lameter
2011-10-14 16:16 ` Dimitri Sivanich
2011-10-18 13:48 ` Dimitri Sivanich
2011-10-18 14:36 ` Christoph Lameter
2011-10-18 15:48 ` Andi Kleen
2011-10-19 1:16 ` David Rientjes [this message]
2011-10-19 14:54 ` Dimitri Sivanich
2011-10-19 15:31 ` Christoph Lameter
2011-10-24 14:59 ` Dimitri Sivanich
[not found] ` <CADE8fzrdMOBF1RyyEpMVi8aKcgOVKRQSKi0=c1Qvh3p6hHcXRA@mail.gmail.com>
2011-10-13 0:07 ` Tim Chen
2011-10-13 14:15 ` Christoph Lameter
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