From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: kosaki.motohiro@jp.fujitsu.com, Shaohua Li <shaohua.li@intel.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"cl@linux.com" <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [experimental][PATCH] mm,vmstat: per cpu stat flush too when per cpu page cache flushed
Date: Tue, 19 Oct 2010 10:34:13 +0900 (JST) [thread overview]
Message-ID: <20101019102428.A1BF.A69D9226@jp.fujitsu.com> (raw)
In-Reply-To: <20101018110829.GZ30667@csn.ul.ie>
> > Initial variable ZVC commit (df9ecaba3f1) says
> >
> > > [PATCH] ZVC: Scale thresholds depending on the size of the system
> > >
> > > The ZVC counter update threshold is currently set to a fixed value of 32.
> > > This patch sets up the threshold depending on the number of processors and
> > > the sizes of the zones in the system.
> > >
> > > With the current threshold of 32, I was able to observe slight contention
> > > when more than 130-140 processors concurrently updated the counters. The
> > > contention vanished when I either increased the threshold to 64 or used
> > > Andrew's idea of overstepping the interval (see ZVC overstep patch).
> > >
> > > However, we saw contention again at 220-230 processors. So we need higher
> > > values for larger systems.
> >
> > So, I'm worry about your patch reintroduce old cache contention issue that Christoph
> > observed when run 128-256cpus system. May I ask how do you think this issue?
>
> It only reintroduces the overhead while kswapd is awake and the system is in danger
> of accidentally allocating all of its pages. Yes, it's slower but it's
> less risky.
When we have rich storage and running IO intensive workload, kswapd are almost
always awake ;)
However, yes, your approach is less risky.
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next prev parent reply other threads:[~2010-10-19 1:34 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-28 5:08 zone state overhead Shaohua Li
2010-09-28 12:39 ` Christoph Lameter
2010-09-28 13:30 ` Mel Gorman
2010-09-28 13:40 ` Christoph Lameter
2010-09-28 13:51 ` Mel Gorman
2010-09-28 14:08 ` Christoph Lameter
2010-09-29 3:02 ` Shaohua Li
2010-09-29 4:02 ` David Rientjes
2010-09-29 4:47 ` Shaohua Li
2010-09-29 5:06 ` David Rientjes
2010-09-29 10:03 ` Mel Gorman
2010-09-29 14:12 ` Christoph Lameter
2010-09-29 14:17 ` Mel Gorman
2010-09-29 14:34 ` Christoph Lameter
2010-09-29 14:41 ` Mel Gorman
2010-09-29 14:45 ` Mel Gorman
2010-09-29 14:54 ` Christoph Lameter
2010-09-29 14:52 ` Christoph Lameter
2010-09-29 19:44 ` David Rientjes
2010-10-08 15:29 ` Mel Gorman
2010-10-09 0:58 ` Shaohua Li
2010-10-11 8:56 ` Mel Gorman
2010-10-12 1:05 ` Shaohua Li
2010-10-12 16:25 ` Mel Gorman
2010-10-13 2:41 ` Shaohua Li
2010-10-13 12:09 ` Mel Gorman
2010-10-13 3:36 ` KOSAKI Motohiro
2010-10-13 6:25 ` [RFC][PATCH 0/3] mm: reserve max drift pages at boot time instead using zone_page_state_snapshot() KOSAKI Motohiro
2010-10-13 6:27 ` [RFC][PATCH 1/3] mm, mem-hotplug: recalculate lowmem_reserve when memory hotplug occur KOSAKI Motohiro
2010-10-13 6:39 ` KAMEZAWA Hiroyuki
2010-10-13 12:59 ` Mel Gorman
2010-10-14 2:44 ` KOSAKI Motohiro
2010-10-13 6:28 ` [RFC][PATCH 2/3] mm: update pcp->stat_threshold " KOSAKI Motohiro
2010-10-13 6:40 ` KAMEZAWA Hiroyuki
2010-10-13 13:02 ` Mel Gorman
2010-10-13 6:32 ` [RFC][PATCH 3/3] mm: reserve max drift pages at boot time instead using zone_page_state_snapshot() KOSAKI Motohiro
2010-10-13 13:19 ` Mel Gorman
2010-10-14 2:39 ` KOSAKI Motohiro
2010-10-18 10:43 ` Mel Gorman
2010-10-13 7:10 ` [experimental][PATCH] mm,vmstat: per cpu stat flush too when per cpu page cache flushed KOSAKI Motohiro
2010-10-13 7:16 ` KAMEZAWA Hiroyuki
2010-10-13 13:22 ` Mel Gorman
2010-10-14 2:50 ` KOSAKI Motohiro
2010-10-15 17:31 ` Christoph Lameter
2010-10-18 9:27 ` KOSAKI Motohiro
2010-10-18 15:44 ` Christoph Lameter
2010-10-19 1:10 ` KOSAKI Motohiro
2010-10-18 11:08 ` Mel Gorman
2010-10-19 1:34 ` KOSAKI Motohiro [this message]
2010-10-19 9:06 ` Mel Gorman
2010-10-18 15:51 ` Christoph Lameter
2010-10-19 0:43 ` KOSAKI Motohiro
2010-10-13 11:24 ` zone state overhead Mel Gorman
2010-10-14 3:07 ` KOSAKI Motohiro
2010-10-18 10:39 ` Mel Gorman
2010-10-19 1:16 ` KOSAKI Motohiro
2010-10-19 9:08 ` Mel Gorman
2010-10-22 14:12 ` Mel Gorman
2010-10-22 15:23 ` Christoph Lameter
2010-10-22 18:45 ` Mel Gorman
2010-10-22 15:27 ` Christoph Lameter
2010-10-22 18:46 ` Mel Gorman
2010-10-22 20:01 ` Christoph Lameter
2010-10-25 4:46 ` KOSAKI Motohiro
2010-10-27 8:19 ` Mel Gorman
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