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    Subject40% IDE performance regression going from FC3 to FC5 with same kernel
    I'll be filing a FC5 performance bug for this but would like an opinion
    from the IDE kernel people just in case this has already been seen...

    I just upgraded my home K7-800, 512MB RAM box from FC3 to FC5
    and noticed a disk performance slowdown while copying files around.

    System has two 160GB disks, a Samsung SP1604N 2MB cache and
    a Maxtor 6Y160P0 8MB cache; both disks appear to be almost 2x
    slower both on hdparm -t tests (17-19MB/s against 33/35 MB/s) and
    on dd tests, like this:

    FC3
    [root@donkey tmp]# time dd if=/dev/hda of=/dev/null skip=200 bs=1024k count=200
    200+0 records in
    200+0 records out

    real 0m4.623s
    user 0m0.004s
    sys 0m1.308s

    FC5
    [root@donkey tmp]# time dd if=/dev/hda of=/dev/null skip=200 bs=1024k count=200
    200+0 records in
    200+0 records out
    209715200 bytes (210 MB) copied, 9.67808 seconds, 21.7 MB/s

    real 0m9.683s
    user 0m0.008s
    sys 0m1.400s


    The initial tests were my last FC3 self-compiled kernel (2.6.16-rc5-git8)
    vs FC5's 2.6.16-1.2080_FC5 kernel; so just to be sure, I copied over
    from my FC3 partition the 2.6.16-rc5-git8 kernel and its config file,
    and rebuilt it under FC5, with just a few differences for the new USB
    2.0 disk I added to a PCI controller I just put in, namely

    [root@donkey linux-2.6.16-rc5-git8]# diff .config
    /fc3/usr/src/linux-2.6.16-rc5-git8/.config
    4c4
    < # Fri Apr 7 03:58:23 2006
    ---
    > # Mon Mar 6 22:49:32 2006
    1110,1112c1110
    < CONFIG_USB_EHCI_HCD=m
    < CONFIG_USB_EHCI_SPLIT_ISO=y
    < CONFIG_USB_EHCI_ROOT_HUB_TT=y
    ---
    > # CONFIG_USB_EHCI_HCD is not set
    1115c1113
    < CONFIG_USB_UHCI_HCD=m
    ---
    > CONFIG_USB_UHCI_HCD=y
    1218d1215
    < # CONFIG_USB_SISUSBVGA is not set

    The result is unexpected - performance delta is still there. Concatenating
    output from hdparm -i /dev/hda and hdparm /dev/hda for the same kernel
    under FC3 and FC5, the only difference is

    [root@donkey ~]# diff /tmp/hdparm.out.2616rc2git8-fc5
    /tmp/hdparm.out.2616rc2git8
    14c14
    < Drive conforms to: (null): ATA/ATAPI-1 ATA/ATAPI-2 ATA/ATAPI-3
    ATA/ATAPI-4 ATA/ATAPI-5 ATA/ATAPI-6 ATA/ATAPI-7
    ---
    > Drive conforms to: (null):
    27c27
    < geometry = 19457/255/63, sectors = 312581808, start = 0
    ---
    > geometry = 19457/255/63, sectors = 160041885696, start = 0

    I'll try now and rebuild a 2.6.16-rc5-git8 kernel under FC5 with the
    FC3 GCC and see whether that is responsible for the performance
    drop... of course if anyone has any idea about what's going on, I
    will be happy to try out stuff. Attaching hdparm output from the FC5
    2.6.16-rc5-git8 just to show that there is DMA etc. all configured fine.


    Thanks in advance, ciao,

    --alessandro

    "Dreamer ? Each one of us is a dreamer. We just push it down deep because
    we are repeatedly told that we are not allowed to dream in real life"
    (Reinhold Ziegler)
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