From: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Lameter <cl@linux.com>
Cc: npiggin@kernel.dk, Pekka Enberg <penberg@cs.helsinki.fi>,
David Rientjes <rientjes@google.com>,
linux-mm@kvack.org, Andi Kleen <andi@firstfloor.org>
Subject: Re: vmscan: Do not run shrinkers for zones other than ZONE_NORMAL
Date: Thu, 21 Oct 2010 13:59:04 -0700 [thread overview]
Message-ID: <20101021135904.48a9c479.akpm@linux-foundation.org> (raw)
In-Reply-To: <alpine.DEB.2.00.1010211547120.32674@router.home>
On Thu, 21 Oct 2010 15:49:33 -0500 (CDT)
Christoph Lameter <cl@linux.com> wrote:
> On Thu, 21 Oct 2010, Andrew Morton wrote:
>
> > On Thu, 21 Oct 2010 15:28:35 -0500 (CDT)
> > Christoph Lameter <cl@linux.com> wrote:
> >
> > > On Thu, 21 Oct 2010, Andrew Morton wrote:
> > >
> > > > The patch changes balance_pgdat() to not shrink slab when inspecting
> > > > the highmem zone. It will therefore change zone balancing behaviour on
> > > > a humble 1G laptop, will it not?
> > >
> > > It will avoid a slab shrink call on the HIGHMEM zone that will put useless
> > > pressure on the cache objects in ZONE_NORMAL and ZONE_DMA. There will have
> > > been already shrinker calls for ZONE_DMA and ZONE_NORMAL before. This is
> > > going to be the third round....
> > >
> >
> > Right, it changes behaviour for modest machines. Apparently accidentally.
> >
> > Is the new behaviour better, or worse?
>
> Its bad given that direct reclaim does one call per scan over all zones.
>
> And it also seems to be useless since all reclaim operates on the same
> data right now. So the call for each zone does the same...
>
> With the per node patch we may be able to get some more finegrained slab
> reclaim in the future. But the subsystems are still not distinguishing
> caches per zone since slab allocations always occur from ZONE_NORMAL. So
> what is the point of the additional calls?
>
In other words, you don't know!
Theoretical design arguments are all well and good. But practical,
empirical results rule, and we don't know the practical, empirical
effects of this change upon our users.
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next prev parent reply other threads:[~2010-10-21 20:59 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-21 17:59 vmscan: Do not run shrinkers for zones other than ZONE_NORMAL Christoph Lameter
2010-10-21 18:00 ` shrinkers: Add node to indicate where to target shrinking Christoph Lameter
2010-10-21 18:12 ` Andi Kleen
2010-10-21 20:57 ` David Rientjes
2010-10-21 21:07 ` Christoph Lameter
2010-10-22 13:27 ` Andi Kleen
2010-10-21 23:58 ` Nick Piggin
2010-10-22 12:12 ` Andi Kleen
2010-10-22 15:55 ` Christoph Hellwig
2010-10-22 16:32 ` Christoph Lameter
2010-10-24 1:42 ` Nick Piggin
2010-10-25 0:57 ` KOSAKI Motohiro
2010-10-25 14:59 ` Christoph Lameter
2010-11-09 4:03 ` Nick Piggin
2010-10-22 16:46 ` Andi Kleen
2010-10-24 1:31 ` Nick Piggin
2010-11-14 2:26 ` Michel Lespinasse
2010-11-14 7:10 ` KOSAKI Motohiro
2010-11-14 11:05 ` Michel Lespinasse
2010-11-15 0:29 ` KOSAKI Motohiro
2010-10-21 18:13 ` vmscan: Do not run shrinkers for zones other than ZONE_NORMAL Andi Kleen
2010-10-21 18:22 ` Christoph Lameter
2010-10-21 18:27 ` Christoph Lameter
2010-10-21 18:33 ` Andi Kleen
2010-10-21 20:48 ` David Rientjes
2010-10-21 20:54 ` Christoph Lameter
2010-10-21 19:40 ` Andrew Morton
2010-10-21 20:03 ` Christoph Lameter
2010-10-21 20:14 ` Andrew Morton
2010-10-21 20:28 ` Christoph Lameter
2010-10-21 20:36 ` Andrew Morton
2010-10-21 20:49 ` Christoph Lameter
2010-10-21 20:59 ` Andrew Morton [this message]
2010-10-21 21:13 ` Christoph Lameter
2010-10-21 21:21 ` Andrew Morton
2010-10-21 23:04 ` Christoph Lameter
2010-10-21 23:56 ` Nick Piggin
2010-10-22 1:37 ` KOSAKI Motohiro
2010-10-22 14:06 ` Christoph Lameter
2010-10-24 1:37 ` Nick Piggin
2010-10-25 1:22 ` KOSAKI Motohiro
2010-10-25 15:07 ` Christoph Lameter
2010-10-26 2:52 ` KOSAKI Motohiro
2010-10-26 12:42 ` KOSAKI Motohiro
2010-10-26 13:10 ` Christoph Lameter
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