linux-kernel - Re: 2.6.24-rc1: First impressions

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Date:	Fri, 26 Oct 2007 22:59:51 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, spamtrap@...bisoft.de,
	linux-kernel@...r.kernel.org, a.p.zijlstra@...llo.nl,
	wfg@...l.ustc.edu.cn, torvalds@...ux-foundation.org,
	riel@...hat.com
Subject: Re: 2.6.24-rc1: First impressions

On Fri, 26 Oct 2007 22:46:57 -0700 Arjan van de Ven <arjan@...radead.org> wrote:

> > > > dd1 - copy 16 GB from /dev/zero to local FS
> > > > dd1-dir - same, but using O_DIRECT for output
> > > > dd2/dd2-dir - copy 2x7.6 GB in parallel from /dev/zero to local FS
> > > > dd3/dd3-dir - copy 3x5.2 GB in parallel from /dev/zero lo local FS
> > > > net1 - copy 5.2 GB from NFS3 share to local FS
> > > > mix3 - copy 3x5.2 GB from /dev/zero to local disk and two NFS3
> > > > shares
> > > > 
> > > >  I did the numbers for 2.6.19.2, 2.6.22.6 and 2.6.24-rc1. All
> > > > units are MB/sec.
> > > > 
> > > > test           2.6.19.2     2.6.22.6    2.6.24.-rc1
> > > > ----------------------------------------------------------------
> > > > dd1                  28           50             96
> > > > dd1-dir              88           88             86
> > > > dd2              2x16.5         2x11         2x44.5
> > > > dd2-dir            2x44         2x44           2x43
> > > > dd3               3x9.8        3x8.7           3x30
> > > > dd3-dir          3x29.5       3x29.5         3x28.5
> > > > net1              30-33        50-55          37-52
> > > > mix3              17/32        25/50          96/35
> > > > (disk/combined-network)
> > > 
> > > wow, really nice results!
> > 
> > Those changes seem suspiciously large to me.  I wonder if there's less
> > physical IO happening during the timed run, and correspondingly more
> > afterwards.
> > 
> 
> another option... this is ext2.. didn't the ext2 reservation stuff get
> merged into -rc1? for ext3 that gave a 4x or so speed boost (much
> better sequential allocation pattern)
> 

Yes, one would expect that to make a large difference in dd2/dd2-dir and
dd3/dd3-dir - but only on SMP.  On UP there's not enough concurrency in the
fs block allocator for any damage to occur.

Reservations won't affect dd1 though, and that went faster too.
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