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    SubjectRe: Strange IDE performance change in 2.6.1-rc1 (again)


    I do not see this behavior and i'm using the same ide chipset driver
    (though not the same ide chipset). btw, readahead for all my other
    drives is set to 8192 during these tests but changing them showed no
    effect on my numbers.



    /dev/hda:

    Model=Maxtor 6Y120P0, FwRev=YAR41VW0, SerialNo=Y40D924E
    Config={ Fixed }
    RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=57
    BuffType=DualPortCache, BuffSize=7936kB, MaxMultSect=16, MultSect=16
    CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=240121728
    IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
    PIO modes: pio0 pio1 pio2 pio3 pio4
    DMA modes: mdma0 mdma1 mdma2
    UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5 udma6
    AdvancedPM=yes: disabled (255) WriteCache=enabled
    Drive conforms to: (null):

    00:07.1 IDE interface: VIA Technologies, Inc.
    VT82C586A/B/VT82C686/A/B/VT8233/A/C/VT8235 PIPC Bus Master IDE (rev 06)

    it's a vt82C686A

    128
    /dev/hda:
    Timing buffered disk reads: 130 MB in 3.05 seconds = 42.69 MB/sec

    256
    /dev/hda:
    Timing buffered disk reads: 134 MB in 3.03 seconds = 44.27 MB/sec

    512
    /dev/hda:
    Timing buffered disk reads: 136 MB in 3.00 seconds = 45.33 MB/sec

    8192
    /dev/hda:
    Timing buffered disk reads: 140 MB in 3.03 seconds = 46.24 MB/sec




    Note, sometimes when moving backwards back to a lower readhead my speed
    does not decrease to the values you see here. readahead on my system
    always goes up (on avg) with higher readahead numbers, maxing at 8192.
    No matter the buffer size or speed or position the ide drive is in.

    hdparm -t is difficult to get really accurate, which is why they suggest
    running it multiple times. I see differences of 4MB/sec on subsequent
    runs without changing anything. run hdparm -t at least 3-4 times for
    each readahead value.

    I suggest trying 128, 256,512,8192 as values for readahead and skip all
    those crap numbers in between.


    if you still see on avg lower numbers on the top end, try nicing hdparm
    to -20. Also, update to a newer hdparm. hdparm v5.4, you seem to be
    using an older one.

    Paolo Ornati wrote:
    > As I have already said I have noticed a strange IDE performance change
    > upgrading from 2.6.0 to 2.6.1-rc1.
    >
    > Now I have more data (and a graph) to show: the test is done using
    > "hdparm -t dev/hda" at various readahead (form 0 to 512).
    >
    > o SCRIPT
    >
    > #!/bin/bash
    >
    > MIN=0
    > MAX=512
    >
    > ra=$MIN
    > while test $ra -le $MAX; do
    > hdparm -a $ra /dev/hda > /dev/null;
    > echo -n $ra$'\t';
    > s1=`hdparm -t /dev/hda | grep 'Timing' | cut -d'=' -f2| cut -d' ' -f2`;
    > s2=`hdparm -t /dev/hda | grep 'Timing' | cut -d'=' -f2| cut -d' ' -f2`;
    > s=`echo "scale=2; ($s1+$s2)/2" | bc`;
    > echo $s;
    > ra=$(($ra+16));
    > done
    >
    >
    > o RESULTS for 2.6.0 (readahead / speed)
    >
    > 0 13.30
    > 16 13.52
    > 32 13.76
    > 48 31.81
    > 64 31.83
    > 80 31.90
    > 96 31.86
    > 112 31.82
    > 128 31.89
    > 144 31.93
    > 160 31.89
    > 176 31.86
    > 192 31.93
    > 208 31.91
    > 224 31.87
    > 240 31.18
    > 256 26.41
    > 272 27.52
    > 288 31.74
    > 304 27.29
    > 320 27.23
    > 336 25.44
    > 352 27.59
    > 368 27.32
    > 384 31.84
    > 400 28.03
    > 416 28.07
    > 432 20.46
    > 448 28.59
    > 464 28.63
    > 480 23.95
    > 496 27.21
    > 512 22.38
    >
    >
    > o RESULTS for 2.6.1-rc1 (readahead / speed)
    >
    > 0 13.34
    > 16 25.86
    > 32 26.27
    > 48 24.81
    > 64 26.26
    > 80 24.88
    > 96 27.09
    > 112 24.88
    > 128 26.31
    > 144 24.79
    > 160 26.31
    > 176 24.51
    > 192 25.86
    > 208 24.35
    > 224 26.48
    > 240 24.82
    > 256 26.38
    > 272 24.60
    > 288 31.15
    > 304 24.61
    > 320 26.69
    > 336 24.54
    > 352 26.23
    > 368 24.87
    > 384 25.91
    > 400 25.74
    > 416 26.45
    > 432 23.61
    > 448 26.44
    > 464 24.36
    > 480 26.80
    > 496 24.60
    > 512 26.49
    >
    >
    > The graph is attached. (x = readahead && y = MB/s)
    >
    > The kernel config for 2.6.0 is attached (for 2.6.1-rc1 I have just used
    > "make oldconfig").
    >
    > INFO on my HD:
    >
    > /dev/hda:
    >
    > Model=WDC WD200BB-53AUA1, FwRev=18.20D18, SerialNo=WD-WMA6Y1501425
    > Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
    > RawCHS=16383/16/63, TrkSize=57600, SectSize=600, ECCbytes=40
    > BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
    > CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=39102336
    > IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
    > PIO modes: pio0 pio1 pio2 pio3 pio4
    > DMA modes: mdma0 mdma1 mdma2
    > UDMA modes: udma0 udma1 udma2 udma3 *udma4 udma5
    > AdvancedPM=no WriteCache=enabled
    > Drive conforms to: device does not report version: 1 2 3 4 5
    >
    > INFO on my IDE controller:
    >
    > 00:04.1 IDE interface: VIA Technologies, Inc. VT82C586/B/686A/B PIPC Bus
    > Master IDE (rev 10)
    >
    >
    > Comments are welcomed.
    >
    > Bye,
    >
    >

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