From: Christoph Hellwig <hch@lst.de>
To: Avi Kivity <avi@redhat.com>
Cc: Chris Webb <chris@arachsys.com>,
balbir@linux.vnet.ibm.com,
KVM development list <kvm@vger.kernel.org>,
Rik van Riel <riel@surriel.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>, Kevin Wolf <kwolf@redhat.com>
Subject: Re: [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter
Date: Wed, 17 Mar 2010 17:52:29 +0100 [thread overview]
Message-ID: <20100317165229.GA29548@lst.de> (raw)
In-Reply-To: <4BA101C5.9040406@redhat.com>
On Wed, Mar 17, 2010 at 06:22:29PM +0200, Avi Kivity wrote:
> They should be reorderable. Otherwise host filesystems on several
> volumes would suffer the same problems.
They are reordable, just not as extremly as the the page cache.
Remember that the request queue really is just a relatively small queue
of outstanding I/O, and that is absolutely intentional. Large scale
_caching_ is done by the VM in the pagecache, with all the usual aging,
pressure, etc algorithms applied to it. The block devices have a
relatively small fixed size request queue associated with it to
facilitate request merging and limited reordering and having fully
set up I/O requests for the device.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Avi Kivity <avi@redhat.com>
Cc: Chris Webb <chris@arachsys.com>,
balbir@linux.vnet.ibm.com,
KVM development list <kvm@vger.kernel.org>,
Rik van Riel <riel@surriel.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>, Kevin Wolf <kwolf@redhat.com>
Subject: Re: [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter
Date: Wed, 17 Mar 2010 17:52:29 +0100 [thread overview]
Message-ID: <20100317165229.GA29548@lst.de> (raw)
In-Reply-To: <4BA101C5.9040406@redhat.com>
On Wed, Mar 17, 2010 at 06:22:29PM +0200, Avi Kivity wrote:
> They should be reorderable. Otherwise host filesystems on several
> volumes would suffer the same problems.
They are reordable, just not as extremly as the the page cache.
Remember that the request queue really is just a relatively small queue
of outstanding I/O, and that is absolutely intentional. Large scale
_caching_ is done by the VM in the pagecache, with all the usual aging,
pressure, etc algorithms applied to it. The block devices have a
relatively small fixed size request queue associated with it to
facilitate request merging and limited reordering and having fully
set up I/O requests for the device.
--
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next prev parent reply other threads:[~2010-03-17 16:53 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-15 7:22 [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter Balbir Singh
2010-03-15 7:22 ` Balbir Singh
2010-03-15 7:48 ` Avi Kivity
2010-03-15 7:48 ` Avi Kivity
2010-03-15 8:07 ` Balbir Singh
2010-03-15 8:07 ` Balbir Singh
2010-03-15 8:27 ` Avi Kivity
2010-03-15 8:27 ` Avi Kivity
2010-03-15 9:17 ` Balbir Singh
2010-03-15 9:17 ` Balbir Singh
2010-03-15 9:27 ` Avi Kivity
2010-03-15 9:27 ` Avi Kivity
2010-03-15 10:45 ` Balbir Singh
2010-03-15 10:45 ` Balbir Singh
2010-03-15 18:48 ` Anthony Liguori
2010-03-15 18:48 ` Anthony Liguori
2010-03-16 9:05 ` Avi Kivity
2010-03-16 9:05 ` Avi Kivity
2010-03-19 7:23 ` Dave Hansen
2010-03-19 7:23 ` Dave Hansen
2010-03-15 20:23 ` Chris Webb
2010-03-15 20:23 ` Chris Webb
2010-03-15 23:43 ` Anthony Liguori
2010-03-15 23:43 ` Anthony Liguori
2010-03-16 0:43 ` Christoph Hellwig
2010-03-16 0:43 ` Christoph Hellwig
2010-03-16 1:27 ` Anthony Liguori
2010-03-16 1:27 ` Anthony Liguori
2010-03-16 8:19 ` Christoph Hellwig
2010-03-16 8:19 ` Christoph Hellwig
2010-03-17 15:14 ` Chris Webb
2010-03-17 15:14 ` Chris Webb
2010-03-17 15:55 ` Anthony Liguori
2010-03-17 15:55 ` Anthony Liguori
2010-03-17 16:27 ` Chris Webb
2010-03-17 16:27 ` Chris Webb
2010-03-22 21:04 ` Chris Webb
2010-03-22 21:04 ` Chris Webb
2010-03-22 21:07 ` Avi Kivity
2010-03-22 21:07 ` Avi Kivity
2010-03-22 21:10 ` Chris Webb
2010-03-22 21:10 ` Chris Webb
2010-03-17 16:27 ` Balbir Singh
2010-03-17 16:27 ` Balbir Singh
2010-03-17 17:05 ` Vivek Goyal
2010-03-17 17:05 ` Vivek Goyal
2010-03-17 19:11 ` Chris Webb
2010-03-17 19:11 ` Chris Webb
2010-03-16 3:16 ` Balbir Singh
2010-03-16 3:16 ` Balbir Singh
2010-03-16 9:17 ` Avi Kivity
2010-03-16 9:17 ` Avi Kivity
2010-03-16 9:54 ` Kevin Wolf
2010-03-16 9:54 ` Kevin Wolf
2010-03-16 10:16 ` Avi Kivity
2010-03-16 10:16 ` Avi Kivity
2010-03-16 10:26 ` Christoph Hellwig
2010-03-16 10:26 ` Christoph Hellwig
2010-03-16 10:36 ` Avi Kivity
2010-03-16 10:36 ` Avi Kivity
2010-03-16 10:44 ` Christoph Hellwig
2010-03-16 10:44 ` Christoph Hellwig
2010-03-16 11:08 ` Avi Kivity
2010-03-16 11:08 ` Avi Kivity
2010-03-16 14:27 ` Balbir Singh
2010-03-16 14:27 ` Balbir Singh
2010-03-16 15:59 ` Avi Kivity
2010-03-16 15:59 ` Avi Kivity
2010-03-17 8:49 ` Christoph Hellwig
2010-03-17 8:49 ` Christoph Hellwig
2010-03-17 9:10 ` Avi Kivity
2010-03-17 9:10 ` Avi Kivity
2010-03-17 15:24 ` Chris Webb
2010-03-17 15:24 ` Chris Webb
2010-03-17 16:22 ` Avi Kivity
2010-03-17 16:22 ` Avi Kivity
2010-03-17 16:40 ` Avi Kivity
2010-03-17 16:40 ` Avi Kivity
2010-03-17 16:47 ` Chris Webb
2010-03-17 16:47 ` Chris Webb
2010-03-17 16:53 ` Avi Kivity
2010-03-17 16:53 ` Avi Kivity
2010-03-17 16:58 ` Christoph Hellwig
2010-03-17 16:58 ` Christoph Hellwig
2010-03-17 17:03 ` Avi Kivity
2010-03-17 17:03 ` Avi Kivity
2010-03-17 16:57 ` Christoph Hellwig
2010-03-17 16:57 ` Christoph Hellwig
2010-03-17 17:06 ` Avi Kivity
2010-03-17 17:06 ` Avi Kivity
2010-03-17 16:52 ` Christoph Hellwig [this message]
2010-03-17 16:52 ` Christoph Hellwig
2010-03-17 17:02 ` Avi Kivity
2010-03-17 17:02 ` Avi Kivity
2010-03-15 15:46 ` Randy Dunlap
2010-03-15 15:46 ` Randy Dunlap
2010-03-16 3:21 ` Balbir Singh
2010-03-16 3:21 ` Balbir Singh
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