From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wu Fengguang <fengguang.wu@gmail.com>
Subject: Re: [Lsf-pc] [dm-devel]  [LSF/MM TOPIC] a few storage topics
Date: Fri, 27 Jan 2012 11:27:34 +0800
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Cc: Vivek Goyal <vgoyal@redhat.com>,
	Andreas Dilger <adilger@dilger.ca>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Jan Kara <jack@suse.cz>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	Mike Snitzer <snitzer@redhat.com>,
	"neilb@suse.de" <neilb@suse.de>,
	"dm-devel@redhat.com" <dm-devel@redhat.com>,
	Christoph Hellwig <hch@infradead.org>,
	Jeff Moyer <jmoyer@redhat.com>,
	Boaz Harrosh <bharrosh@panasas.com>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"lsf-pc@lists.linux-foundation.org"
	<lsf-pc@lists.linux-foundation.org>,
	Chris Mason <chris.mason@oracle.com>,
	"Darrick J.Wong" <djwong@us.ibm.com>
To: Dave Chinner <david@fromorbit.com>
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On Fri, Jan 27, 2012 at 09:34:49AM +1100, Dave Chinner wrote:
> On Thu, Jan 26, 2012 at 11:25:56AM -0500, Vivek Goyal wrote:
> > On Wed, Jan 25, 2012 at 02:35:52PM +0800, Wu Fengguang wrote:
> > > > It would also be
> > > > possible to trigger on the size of the device so that the 32MB USB stick
> > > > doesn't sit busy for a minute with readahead that is useless.
> > > 
> > > Yeah, I do have a patch for shrinking readahead size based on device size.
> > 
> > Should it be a udev rule to change read_ahead_kb on device based on device
> > size, instead of a kernel patch?
> 
> That's effectively what vendors like SGI have been doing since udev
> was first introduced, though more often the rules are based on device
> type rather than size. e.g. a 64GB device might be a USB flash drive
> now, but a 40GB device might be a really fast SSD....

Fair enough. I'll drop this kernel policy patch 

        block: limit default readahead size for small devices
        https://lkml.org/lkml/2011/12/19/89

Thanks,
Fengguang