From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, npiggin@kernel.dk,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cl@linux.com,
kamezawa.hiroyu@jp.fujitsu.com, Mel Gorman <mel@csn.ul.ie>,
Minchan Kim <minchan.kim@gmail.com>
Subject: Re: [PATCH 0/3] Unmapped page cache control (v5)
Date: Fri, 1 Apr 2011 23:34:55 +0530 [thread overview]
Message-ID: <20110401180455.GU2879@balbir.in.ibm.com> (raw)
In-Reply-To: <20110401222250.A894.A69D9226@jp.fujitsu.com>
* KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2011-04-01 22:21:26]:
> > * KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2011-04-01 16:56:57]:
> >
> > > Hi
> > >
> > > > > 1) zone reclaim doesn't work if the system has multiple node and the
> > > > > workload is file cache oriented (eg file server, web server, mail server, et al).
> > > > > because zone recliam make some much free pages than zone->pages_min and
> > > > > then new page cache request consume nearest node memory and then it
> > > > > bring next zone reclaim. Then, memory utilization is reduced and
> > > > > unnecessary LRU discard is increased dramatically.
> > > > >
> > > > > SGI folks added CPUSET specific solution in past. (cpuset.memory_spread_page)
> > > > > But global recliam still have its issue. zone recliam is HPC workload specific
> > > > > feature and HPC folks has no motivation to don't use CPUSET.
> > > >
> > > > I am afraid you misread the patches and the intent. The intent to
> > > > explictly enable control of unmapped pages and has nothing
> > > > specifically to do with multiple nodes at this point. The control is
> > > > system wide and carefully enabled by the administrator.
> > >
> > > Hm. OK, I may misread.
> > > Can you please explain the reason why de-duplication feature need to selectable and
> > > disabled by defaut. "explicity enable" mean this feature want to spot corner case issue??
> >
> > Yes, because given a selection of choices (including what you
> > mentioned in the review), it would be nice to have
> > this selectable.
>
> It's no good answer. :-/
I am afraid I cannot please you with my answers
> Who need the feature and who shouldn't use it? It this enough valuable for enough large
> people? That's my question point.
>
You can see the use cases documented, including when running Linux as
a guest under other hypervisors, today we have a choice of not using
host page cache with cache=none, but nothing the other way round.
There are other use cases for embedded folks (in terms of controlling
unmapped page cache), please see previous discussions.
--
Three Cheers,
Balbir
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next prev parent reply other threads:[~2011-04-01 18:06 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-30 5:30 [PATCH 0/3] Unmapped page cache control (v5) Balbir Singh
2011-03-30 5:31 ` [PATCH 1/3] Move zone_reclaim() outside of CONFIG_NUMA (v5) Balbir Singh
2011-03-30 5:31 ` [PATCH 2/3] Refactor zone_reclaim code (v5) Balbir Singh
2011-03-30 5:32 ` [PATCH 3/3] Provide control over unmapped pages (v5) Balbir Singh
2011-03-30 23:35 ` Andrew Morton
2011-03-31 5:52 ` Balbir Singh
2011-03-30 23:36 ` [PATCH 0/3] Unmapped page cache control (v5) Andrew Morton
2011-03-31 5:27 ` Balbir Singh
2011-03-31 5:32 ` Andrew Morton
2011-04-01 17:31 ` Balbir Singh
2011-03-31 5:40 ` KOSAKI Motohiro
2011-03-31 8:28 ` Balbir Singh
2011-04-01 7:56 ` KOSAKI Motohiro
2011-04-01 13:12 ` Balbir Singh
2011-04-01 13:21 ` KOSAKI Motohiro
2011-04-01 18:04 ` Balbir Singh [this message]
2011-04-03 9:39 ` KOSAKI Motohiro
2011-03-31 20:13 ` Christoph Lameter
2011-04-01 13:17 ` KOSAKI Motohiro
2011-04-01 14:50 ` Christoph Lameter
2011-04-03 9:44 ` KOSAKI Motohiro
2011-04-03 18:45 ` Christoph Lameter
2011-04-01 23:10 ` Satoru Moriya
2011-04-02 1:10 ` Dave Chinner
2011-04-03 9:32 ` KOSAKI Motohiro
2011-04-04 0:19 ` Dave Chinner
2011-04-04 12:05 ` KOSAKI Motohiro
2011-04-03 18:41 ` Christoph Lameter
2011-03-31 21:40 ` Dave Chinner
2011-04-01 3:08 ` Balbir Singh
2011-04-01 5:31 ` Dave Chinner
2011-04-01 3:18 ` KOSAKI Motohiro
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