Re: 2.6.24-rc1: First impressions

From: Andrew Morton
Date: Sat Oct 27 2007 - 02:00:52 EST

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