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    SubjectRe: 2.6.24-rc1: First impressions
    On Fri, 26 Oct 2007 12:21:55 -0700
    Andrew Morton <akpm@linux-foundation.org> wrote:

    > On Fri, 26 Oct 2007 17:22:21 +0200
    > Ingo Molnar <mingo@elte.hu> wrote:
    >
    > >
    > > * Martin Knoblauch <spamtrap@knobisoft.de> wrote:
    > >
    > > > Hi ,
    > > >
    > > > just to give some feedback on 2.6.24-rc1. For some time I am
    > > > tracking IO/writeback problems that hurt system responsiveness
    > > > big-time. I tested Peters stuff together with Fenguangs additions
    > > > and it looked promising. Therefore I was very happy to see Peters
    > > > stuff going into 2.6.24 and waited eagerly for rc1. In short, I
    > > > am impressed. This really looks good. IO throughput is great and
    > > > I could not reproduce the responsiveness problems so far.
    > > >
    > > > Below are a some numbers of my brute-force I/O tests that I can
    > > > use to bring responsiveness down. My platform is a HP/DL380g4,
    > > > dual CPUs, HT-enabled, 8 GB Memory, SmartaArray6i controller with
    > > > 4x72GB SCSI disks as RAID5 (battery protected writeback cahe
    > > > enabled) and gigabit networking (tg3). User space is 64-bit
    > > > RHEL4.3
    > > >
    > > > I am basically doing copies using "dd" with 1MB blocksize. Local
    > > > Filesystem ist ext2 (noatime). IO-Scheduler is dealine, as it
    > > > tends to give best results. NFS3 Server is a Sun/T2000/Solaris10.
    > > > The tests are:
    > > >
    > > > 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)

    (or maybe I'm just wrong)
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