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    SubjectRe: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28
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    Date
    On Wed, 2008-09-17 at 15:57 +0200, Mike Galbraith wrote:
    > On Wed, 2008-09-17 at 16:36 +0300, Ilpo Järvinen wrote:
    > > On Wed, 17 Sep 2008, Mike Galbraith wrote:
    > >
    > > > On Wed, 2008-09-17 at 14:49 +0200, Ingo Molnar wrote:
    > > >
    > > > > git log --pretty=format:"%h: %s" 2069f45..847106f | grep -viE \
    > > > > 'block|alsa|pcmcia|sound|Merge|iosched|blk|DAC960|scsi|s390|paride|pktcdvd|filter|cdrom|drm'
    > > > >
    > > > > gives us:
    > > > >
    > > > > 7daf705: Start using the new '%pS' infrastructure to print symbols
    > > > > 6f0f0fd: security: remove register_security hook
    > > > > 93cbace: security: remove dummy module fix
    > > > > 5915eb5: security: remove dummy module
    > > > > b478a9f: security: remove unused sb_get_mnt_opts hook
    > > > > 32502b8: splice: fix generic_file_splice_read() race with page invalidation
    > > > > 8b3d356: ramfs: enable splice write
    > > > > a144ff0: xen: Avoid allocations causing swap activity on the resume path
    > > > >
    > > > > which really only leaves that security commit your bisection fingered.
    > > > > Which _slightly_ raises its likelyhood of being implicated. Structure
    > > > > size changes can move two formerly far-apart netperf-relevant symbols on
    > > > > the same cacheline, which can start cache ping-pong-ing badly.
    > > >
    > > > I sure hope it's something like ping-pong, it's driving me NUTS.
    > >
    > > How about dividing the problem to smaller blocks then by restoring
    > > parts of the change...
    >
    > Well, what I've done is check out the "bad" tree, reverted every darn
    > commit between there and the "good" tree, and then reverted the reverts
    > so I have a nice merge-free line and don't have to remember to think
    > backward. (probably sounds silly to git-foo masters) I'll try
    > bisecting that in the a.m. and see what happens.

    It bisected to 1c9ce52. Reverting that in 27.git had the expected
    result, nada. Full bisection/test log below - you can jump straight to
    post run sanity checks. I'm torn between building a straight line tree
    from v2.6.26 through git.today and bisecting that sucker, or exorcising
    netperf from my box and swearing a sacred oath to never download the
    damned thing again. Nuking netperf is most attractive option.

    1e65e841bb5584136ed6047c55cf77532afbbb55 is first bad commit
    commit 1e65e841bb5584136ed6047c55cf77532afbbb55
    Author: Mike Galbraith <efault@gmx.de>
    Date: Wed Sep 17 14:55:50 2008 +0200

    Revert "Revert "block: export "ro" attribute""

    This reverts commit 2c8803af5c1bf41200167f29349f7f1396683a51.

    :040000 040000 08ca8ba7ff3f9506a5462b4122256356cae28ceb bef679485bc924ad1dc867858ebda1b68196b5a8 M block


    git bisect start
    # good: [7804ad865f7d0cd9bdc51da601772ce4d2e252ca] Revert "[ALSA] soc - tlv320aic3x - revisit clock setup"
    git bisect good 7804ad865f7d0cd9bdc51da601772ce4d2e252ca
    # bad: [2846693a63a34ac6d582dd55a7e00605b49b1cec] Revert "Revert "[S390] sclp_tty: Fix scheduling while atomic bug.""
    git bisect bad 2846693a63a34ac6d582dd55a7e00605b49b1cec
    # bad: [70477f86f63640be2dd1d8968aeb47870a5c21c6] Revert "Revert "xen/blkfront: Make sure we don't use bounce buffers, we don't need them.""
    git bisect bad 70477f86f63640be2dd1d8968aeb47870a5c21c6
    # good: [7c6ccb520424939deff0a50f3fae621c6477dbbe] Revert "Revert "ALSA: hda - Add bdl_pos_adj option""
    git bisect good 7c6ccb520424939deff0a50f3fae621c6477dbbe
    # good: [66036beae94f043f99044e285935486126a9c4bd] Revert "Revert "pcmcia: fix Alchemy warnings""
    git bisect good 66036beae94f043f99044e285935486126a9c4bd
    # good: [6b7b5ef18871c8f7c15eedc6eb53270eaf8bc613] Revert "Revert "ALSA: hda - Added SSID for 'Fujitsu Siemens Amilo M1451G' laptop""
    git bisect good 6b7b5ef18871c8f7c15eedc6eb53270eaf8bc613
    # good: [024905ea4b2d1ab5d6b845ba84ddfc0857fb2d2a] Revert "Revert "ALSA: hda - Add MacBook 3.1 support""
    git bisect good 024905ea4b2d1ab5d6b845ba84ddfc0857fb2d2a
    # good: [4bbe3501e06eddaa4900894efa519f1167cb8624] Revert "Revert "as-iosched: properly protect ioc_gone and ioc count""
    git bisect good 4bbe3501e06eddaa4900894efa519f1167cb8624
    # good: [e124683c1cd5c73c494f9ea6cee8a71e68bb70ca] Revert "Revert "Added in user-injected messages into blk traces""
    git bisect good e124683c1cd5c73c494f9ea6cee8a71e68bb70ca
    # bad: [f148fae0bc009aa23122c5762368a1a16bb55b86] Revert "Revert "block: kill request_queue_t""
    git bisect bad f148fae0bc009aa23122c5762368a1a16bb55b86
    # bad: [1e65e841bb5584136ed6047c55cf77532afbbb55] Revert "Revert "block: export "ro" attribute""
    git bisect bad 1e65e841bb5584136ed6047c55cf77532afbbb55


    v2.6.26-974-g2846693 (847106f)
    16384 87380 1 1 60.00 94350.45
    16384 87380 1 1 60.01 95857.25
    16384 87380 1 1 60.00 95334.84
    16384 87380 1 1 60.00 95052.11

    v2.6.26-659-g7804ad8 (2069f45)
    16384 87380 1 1 60.00 98630.64
    16384 87380 1 1 60.00 98653.14
    16384 87380 1 1 60.00 99162.65
    16384 87380 1 1 60.00 98652.38

    v2.6.26-816-g70477f8 (call it bad)
    16384 87380 1 1 60.00 95532.19
    16384 87380 1 1 60.01 96211.39
    16384 87380 1 1 60.01 96246.73
    16384 87380 1 1 60.01 96286.40

    v2.6.26-737-g7c6ccb5
    16384 87380 1 1 60.00 98478.00
    16384 87380 1 1 60.00 99221.33
    16384 87380 1 1 60.00 98930.70
    16384 87380 1 1 60.00 98958.73

    v2.6.26-776-g66036be
    16384 87380 1 1 60.00 97958.10
    16384 87380 1 1 60.01 98683.80
    16384 87380 1 1 60.01 98515.34
    16384 87380 1 1 60.00 98396.11

    v2.6.26-796-g6b7b5ef
    16384 87380 1 1 60.00 99047.21
    16384 87380 1 1 60.00 98095.23
    16384 87380 1 1 60.00 99811.18
    16384 87380 1 1 60.00 98651.32

    v2.6.26-806-g024905e
    16384 87380 1 1 60.00 98823.46
    16384 87380 1 1 60.00 98959.11
    16384 87380 1 1 60.00 98709.95
    16384 87380 1 1 60.00 99042.13

    v2.6.26-811-g4bbe350
    16384 87380 1 1 60.00 98144.99
    16384 87380 1 1 60.01 99023.30
    16384 87380 1 1 60.01 98685.45
    16384 87380 1 1 60.01 98606.18

    v2.6.26-813-ge124683
    16384 87380 1 1 60.00 98458.18
    16384 87380 1 1 60.00 98163.92
    16384 87380 1 1 60.00 98115.62
    16384 87380 1 1 60.00 98633.62

    v2.6.26-815-gf148fae
    16384 87380 1 1 60.00 95649.91
    16384 87380 1 1 60.00 96292.34
    16384 87380 1 1 60.00 96043.82
    16384 87380 1 1 60.00 96093.81

    v2.6.26-814-g1e65e84
    16384 87380 1 1 60.00 94906.81
    16384 87380 1 1 60.00 95445.05
    16384 87380 1 1 60.01 94698.68
    16384 87380 1 1 60.00 94938.65

    Post bisection checkouts
    ------------------------------------------------
    v2.6.26-rc8-208-g02c6230
    16384 87380 1 1 60.00 98392.94
    16384 87380 1 1 60.00 98199.96
    16384 87380 1 1 60.00 98534.27
    16384 87380 1 1 60.00 98501.02

    v2.6.26-rc8-209-g1c9ce52
    16384 87380 1 1 60.00 97583.88
    16384 87380 1 1 60.00 97326.23
    16384 87380 1 1 60.00 97582.80
    16384 87380 1 1 60.00 97568.63

    v2.6.26-814-g1e65e84
    16384 87380 1 1 60.00 94856.33
    16384 87380 1 1 60.00 94594.03
    16384 87380 1 1 60.00 94751.74
    16384 87380 1 1 60.01 96825.28

    v2.6.26-813-ge124683
    16384 87380 1 1 60.00 97550.64
    16384 87380 1 1 60.00 98024.28
    16384 87380 1 1 60.00 98486.85
    16384 87380 1 1 60.00 98493.41


    marge:..git/linux-2.6 # git rev-list v2.6.26-813-ge124683..v2.6.26-814-g1e65e84
    1e65e841bb5584136ed6047c55cf77532afbbb55
    marge:..git/linux-2.6 # git show 1e65e841bb5584136ed6047c55cf77532afbbb55

    commit 1e65e841bb5584136ed6047c55cf77532afbbb55
    Author: Mike Galbraith <efault@gmx.de>
    Date: Wed Sep 17 14:55:50 2008 +0200

    Revert "Revert "block: export "ro" attribute""

    This reverts commit 2c8803af5c1bf41200167f29349f7f1396683a51.

    diff --git a/block/genhd.c b/block/genhd.c
    index b922d48..43e468e 100644
    --- a/block/genhd.c
    +++ b/block/genhd.c
    @@ -400,6 +400,14 @@ static ssize_t disk_removable_show(struct device *dev,
    (disk->flags & GENHD_FL_REMOVABLE ? 1 : 0));
    }

    +static ssize_t disk_ro_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + struct gendisk *disk = dev_to_disk(dev);
    +
    + return sprintf(buf, "%d\n", disk->policy ? 1 : 0);
    +}
    +
    static ssize_t disk_size_show(struct device *dev,
    struct device_attribute *attr, char *buf)
    {
    @@ -472,6 +480,7 @@ static ssize_t disk_fail_store(struct device *dev,

    static DEVICE_ATTR(range, S_IRUGO, disk_range_show, NULL);
    static DEVICE_ATTR(removable, S_IRUGO, disk_removable_show, NULL);
    +static DEVICE_ATTR(ro, S_IRUGO, disk_ro_show, NULL);
    static DEVICE_ATTR(size, S_IRUGO, disk_size_show, NULL);
    static DEVICE_ATTR(capability, S_IRUGO, disk_capability_show, NULL);
    static DEVICE_ATTR(stat, S_IRUGO, disk_stat_show, NULL);
    @@ -483,6 +492,7 @@ static struct device_attribute dev_attr_fail =
    static struct attribute *disk_attrs[] = {
    &dev_attr_range.attr,
    &dev_attr_removable.attr,
    + &dev_attr_ro.attr,
    &dev_attr_size.attr,
    &dev_attr_capability.attr,
    &dev_attr_stat.attr,

    --
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