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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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