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SubjectRe: 2.6.24-rc1: First impressions
----- Original Message ----
> From: Ingo Molnar <mingo@elte.hu>
> To: Andrew Morton <akpm@linux-foundation.org>
> Cc: spamtrap@knobisoft.de; linux-kernel@vger.kernel.org; a.p.zijlstra@chello.nl; wfg@mail.ustc.edu.cn; torvalds@linux-foundation.org; riel@redhat.com
> Sent: Friday, October 26, 2007 9:33:40 PM
> Subject: Re: 2.6.24-rc1: First impressions
>
> * Andrew Morton 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.
>
> so a final 'sync' should be added to the test too, and the time
> it
>
takes
> factored into the bandwidth numbers?
>

One of the reasons I do 15 GB transfers is to make sure that I am well above the possible page cache size. And of course I am doing a final sync to finish the runs :-) The sync is also running faster in 2.6.24-rc1.

If I factor it in the results for dd1/dd3 are:

test 2.6.19.2 2.6.22.6 2.6.24-rc1
sync time 18sec 19sec 6sec
dd1 27.5 47.5 92
dd3 3x9.1 3x8.5 3x29

So basically including the sync time make 2.6.24-rc1 even more promosing. Now, I know that my benchmarks numbers are crude and show only a very small aspect of system performance. But - it is an aspect I care about a lot. And those benchmarks match my use-case pretty good.

Cheers
Martin





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