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    SubjectRe: Linux 2.6.6 "IDE cache-flush at shutdown fixes"
    Bartlomiej Zolnierkiewicz wrote:

    >>Vanilla 2.6.6:
    >>
    >>rene@7ixe4:~/cache$ grep wcache settings-2.6.6
    >>wcache 1 0 1 rw
    >>
    >>2.6.6 with the de{flush,spin}ification patches:
    >>
    >>rene@7ixe4:~/cache$ grep wcache settings-2.6.6-hackedup
    >>wcache 0 0 1 rw
    >>
    >>Hrmpf. 0?
    >
    > Very interesting, can you try vanilla 2.6.5 (or some other 2.6.x)?

    2.4.26 : wcache = 0, 0, 1
    2.6.6-rc3-mm2 : wcache = 0, 0, 1
    2.6.6 : wcache = 1, 0, 1
    2.6.6-hackedup : wcache = 0, 0, 1

    (on none of these hdparm -W0/1 has any effect, by the way)

    > We are getting close to the real problem.

    Indeed. I have attached two "tiobench" seq. write results, one for
    vanilla 2.6.6, and one for 2.6.6-hackedup (your changes). I remember the
    result for the latter are the normal ones I got with previous kernels as
    well. The differences are very interesting.

    2.6.6-vanilla (ie, the one showing wcache=1): +/- 10MB/s
    2.6.6-hackedup (ie, shows wcache=0) : +/- 46MB/s

    As said, that 46 is the expected value. Is this a logic inversion bug in
    either driver (but then both 2.4.26 and 2.6) or drive firmware?

    Rene.

    Sequential Writes
    File Blk Num Avg Maximum Lat% Lat% CPU
    Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
    ---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
    2.6.6 1534 4096 1 10.74 9.440% 0.298 2641.08 0.00102 0.00000 114
    2.6.6 1534 4096 2 10.64 9.999% 0.586 7005.74 0.00331 0.00000 106
    2.6.6 1534 4096 4 10.64 9.730% 1.129 17964.34 0.02550 0.00025 109
    2.6.6 1534 4096 8 10.12 9.423% 2.099 28425.08 0.04065 0.00256 107
    Sequential Writes
    File Blk Num Avg Maximum Lat% Lat% CPU
    Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
    ---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
    2.6.6 1534 4096 1 46.59 57.01% 0.069 598.21 0.00000 0.00000 82
    2.6.6 1534 4096 2 42.44 50.34% 0.155 1951.60 0.00000 0.00000 84
    2.6.6 1534 4096 4 44.65 52.23% 0.267 1336.76 0.00000 0.00000 85
    2.6.6 1534 4096 8 37.78 41.34% 0.604 6720.81 0.00307 0.00000 91
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