From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff Moyer <jmoyer@redhat.com>
Subject: Re: [dm-devel] [Lsf-pc] [LSF/MM TOPIC] a few storage topics
Date: Tue, 24 Jan 2012 14:11:55 -0500
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Cc: Andreas Dilger <adilger@dilger.ca>,
	Chris Mason <chris.mason@oracle.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Jan Kara <jack@suse.cz>, Boaz Harrosh <bharrosh@panasas.com>,
	Mike Snitzer <snitzer@redhat.com>,
	"linux-scsi\@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"neilb\@suse.de" <neilb@suse.de>,
	"dm-devel\@redhat.com" <dm-devel@redhat.com>,
	"linux-fsdevel\@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"lsf-pc\@lists.linux-foundation.org"
	<lsf-pc@lists.linux-foundation.org>,
	"Darrick J.Wong" <djwong@us.ibm.com>
To: Christoph Hellwig <hch@infradead.org>
Return-path: <linux-scsi-owner@vger.kernel.org>
In-Reply-To: <20120124184054.GA23227@infradead.org> (Christoph Hellwig's
	message of "Tue, 24 Jan 2012 13:40:54 -0500")
Sender: linux-scsi-owner@vger.kernel.org
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Christoph Hellwig <hch@infradead.org> writes:

> All three filesystems use the generic mpages code for reads, so they
> all get the same (bad) I/O patterns.  Looks like we need to fix this up
> ASAP.

Actually, in discussing this with Vivek, he mentioned that read ahead
might be involved.  Sure enough, after bumping read_ahead_kb, 1MB I/Os
are sent down to the storage (for xfs anyway).

Cheers,
Jeff