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: Wed, 25 Jan 2012 11:29:32 +0800
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Cc: Jeff Moyer <jmoyer@redhat.com>, Andreas Dilger <adilger@dilger.ca>,
	Andrea Arcangeli <aarcange@redhat.com>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	Mike Snitzer <snitzer@redhat.com>,
	"neilb@suse.de" <neilb@suse.de>,
	Christoph Hellwig <hch@infradead.org>,
	"dm-devel@redhat.com" <dm-devel@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: Jan Kara <jack@suse.cz>
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On Tue, Jan 24, 2012 at 09:39:36PM +0100, Jan Kara wrote:
> On Tue 24-01-12 15:13:40, Jeff Moyer wrote:
[snip]
> > > Maybe 128 KB is a too small default these days but OTOH noone prevents you
> > > from raising it (e.g. SLES uses 1 MB as a default).
> > 
> > For some reason, I thought it had been bumped to 512KB by default.  Must
> > be that overactive imagination I have...  Anyway, if all of the distros
> > start bumping the default, don't you think it's time to consider bumping
> > it upstream, too?  I thought there was a lot of work put into not being
> > too aggressive on readahead, so the downside of having a larger
> > read_ahead_kb setting was fairly small.
>   Yeah, I believe 512KB should be pretty safe these days except for
> embedded world. OTOH average desktop user doesn't really care so it's
> mostly servers with beefy storage that care... (note that I wrote we raised
> the read_ahead_kb for SLES but not for openSUSE or SLED (desktop enterprise
> distro)).

Maybe we don't need to care much about the embedded world when raising
the default readahead size? Because even the current 128KB is too much
for them, and I see Android setting the readahead size to 4KB...

Some time ago I posted a series for raising the default readahead size
to 512KB. But I'm open to use 1MB now (shall we vote on it?).

Thanks,
Fengguang