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From: Christoph Lameter <cl@linux.com>
To: Bron Gondwana <brong@fastmail.fm>
Cc: Robert Mueller <robm@fastmail.fm>,
	Shaohua Li <shaohua.li@intel.com>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>, Mel Gorman <mel@csn.ul.ie>
Subject: Re: Default zone_reclaim_mode = 1 on NUMA kernel is bad for file/email/web servers
Date: Fri, 17 Sep 2010 09:22:00 -0500 (CDT)	[thread overview]
Message-ID: <alpine.DEB.2.00.1009170916130.11900@router.home> (raw)
In-Reply-To: <20100917140916.GA8474@brong.net>

On Sat, 18 Sep 2010, Bron Gondwana wrote:

> > From the first look that seems to be the problem. You do not need to be
> > bound to a particular cpu, the scheduler will just leave a single process
> > on the same cpu by default. If you then allocate all memory only from this
> > process then you get the scenario that you described.
>
> Huh?  Which bit of forking server makes you think one process is allocating
> lots of memory?  They're opening and reading from files.  Unless you're
> calling the kernel a "single process".

I have no idea what your app does. The data that I glanced over looks as
if most allocations happen for a particular memory node and since the
memory is optimized to be local to that node other memory is not used
intensively. This can occur because of allocations through one process /
thread that is always running on the same cpu and therefore always
allocates from the memory node local to that cpu.

It can also happen f.e. if a driver always allocates memory local to the
I/O bus that it is using.


WARNING: multiple messages have this Message-ID (diff)
From: Christoph Lameter <cl@linux.com>
To: Bron Gondwana <brong@fastmail.fm>
Cc: Robert Mueller <robm@fastmail.fm>,
	Shaohua Li <shaohua.li@intel.com>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>, Mel Gorman <mel@csn.ul.ie>
Subject: Re: Default zone_reclaim_mode = 1 on NUMA kernel is bad for file/email/web servers
Date: Fri, 17 Sep 2010 09:22:00 -0500 (CDT)	[thread overview]
Message-ID: <alpine.DEB.2.00.1009170916130.11900@router.home> (raw)
In-Reply-To: <20100917140916.GA8474@brong.net>

On Sat, 18 Sep 2010, Bron Gondwana wrote:

> > From the first look that seems to be the problem. You do not need to be
> > bound to a particular cpu, the scheduler will just leave a single process
> > on the same cpu by default. If you then allocate all memory only from this
> > process then you get the scenario that you described.
>
> Huh?  Which bit of forking server makes you think one process is allocating
> lots of memory?  They're opening and reading from files.  Unless you're
> calling the kernel a "single process".

I have no idea what your app does. The data that I glanced over looks as
if most allocations happen for a particular memory node and since the
memory is optimized to be local to that node other memory is not used
intensively. This can occur because of allocations through one process /
thread that is always running on the same cpu and therefore always
allocates from the memory node local to that cpu.

It can also happen f.e. if a driver always allocates memory local to the
I/O bus that it is using.

--
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  reply	other threads:[~2010-09-17 14:22 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-13  3:39 Default zone_reclaim_mode = 1 on NUMA kernel is bad for file/email/web servers Robert Mueller
2010-09-16 10:01 ` KOSAKI Motohiro
2010-09-16 10:01   ` KOSAKI Motohiro
2010-09-16 17:06   ` Christoph Lameter
2010-09-16 17:06     ` Christoph Lameter
2010-09-17  0:50     ` Robert Mueller
2010-09-17  0:50       ` Robert Mueller
2010-09-17  6:01       ` Shaohua Li
2010-09-17  6:01         ` Shaohua Li
2010-09-17  7:32         ` Robert Mueller
2010-09-17  7:32           ` Robert Mueller
2010-09-17 13:56           ` Christoph Lameter
2010-09-17 13:56             ` Christoph Lameter
2010-09-17 14:09             ` Bron Gondwana
2010-09-17 14:09               ` Bron Gondwana
2010-09-17 14:22               ` Christoph Lameter [this message]
2010-09-17 14:22                 ` Christoph Lameter
2010-09-17 23:01                 ` Bron Gondwana
2010-09-17 23:01                   ` Bron Gondwana
2010-09-20  9:34   ` Mel Gorman
2010-09-20  9:34     ` Mel Gorman
2010-09-20 23:41     ` Default zone_reclaim_mode = 1 on NUMA kernel is bad forfile/email/web servers Rob Mueller
2010-09-20 23:41       ` Rob Mueller
2010-09-21  9:04       ` Mel Gorman
2010-09-21  9:04         ` Mel Gorman
2010-09-21 14:14         ` Christoph Lameter
2010-09-21 14:14           ` Christoph Lameter
2010-09-22  3:44           ` Rob Mueller
2010-09-22  3:44             ` Rob Mueller
2010-09-27  2:01         ` KOSAKI Motohiro
2010-09-27  2:01           ` KOSAKI Motohiro
2010-09-27 13:53           ` Christoph Lameter
2010-09-27 13:53             ` Christoph Lameter
2010-09-27 23:17             ` Robert Mueller
2010-09-27 23:17               ` Robert Mueller
2010-09-28 12:35               ` Christoph Lameter
2010-09-28 12:35                 ` Christoph Lameter
2010-09-28 12:42                 ` Bron Gondwana
2010-09-28 12:42                   ` Bron Gondwana
2010-09-28 12:49                   ` Christoph Lameter
2010-09-28 12:49                     ` Christoph Lameter
2010-09-30  7:05             ` Andi Kleen
2010-09-30  7:05               ` Andi Kleen
2010-10-04 12:45             ` KOSAKI Motohiro
2010-10-04 12:45               ` KOSAKI Motohiro
2010-10-04 13:07               ` Christoph Lameter
2010-10-04 13:07                 ` Christoph Lameter
2010-10-05  5:32                 ` KOSAKI Motohiro
2010-10-05  5:32                   ` KOSAKI Motohiro
2010-10-04 19:43               ` David Rientjes
2010-10-04 19:43                 ` David Rientjes
2010-09-21  1:05   ` Default zone_reclaim_mode = 1 on NUMA kernel is bad for file/email/web servers KAMEZAWA Hiroyuki
2010-09-21  1:05     ` KAMEZAWA Hiroyuki
2010-09-27  2:04     ` KOSAKI Motohiro
2010-09-27  2:04       ` KOSAKI Motohiro
2010-09-27  2:06       ` KAMEZAWA Hiroyuki
2010-09-27  2:06         ` KAMEZAWA Hiroyuki
2010-09-23 11:44   ` Balbir Singh
2010-09-23 11:44     ` Balbir Singh
2010-09-30  8:38   ` Bron Gondwana
2010-09-30  8:38     ` Bron Gondwana

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