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    SubjectRe: Very poor performance with 2.6.4
    Chris Mason wrote:
    > On Mon, 2004-03-29 at 01:16, Andreas Hartmann wrote:
    >> Andrew Morton wrote:
    >> > Andreas Hartmann <andihartmann@freenet.de> wrote:
    >> >>
    >> >> I tested kernel 2.6.4. While compiling kdelibs and kdebase, I felt, that
    >> >> kernel 2.6 seems to be slower than 2.4.25.
    >> >>
    >> >> So I did some tests to compare the performance directly. Therefore I
    >> >> rebooted for everey test in init 2 (no X).
    >> >>
    >> >> I locally compiled 2.6.5rc2 3 times under 2.6.4 and under 2.4.25 on a
    >> >> reiserfs LVM partition, which resides onto a IDE HD (using DMA) and got
    >> >> the following result:
    >> >>
    >> >> In the middle, compiling under kernel 2.6.4 tooks 9.3% more real time than
    >> >> under 2.4.25.
    >> >> The user-processortime is about the same, but the system-processortime is
    >> >> under 2.6.4 32.9% higher than under 2.4.25.
    >> >
    >> > Try mounting your reiserfs filesystems with the `-o nolargeio=1' option.
    >>
    >> This didn't help.
    >>
    >> >
    >> > If that doesn't help, please run a comparative kernel profile. See
    >> > Documentation/basic_profiling.txt.
    >>
    >> I'll do this next.
    >
    > You might also want to try 2.6.5-rc2 which has a set of reiserfs fixes
    > from 2.4.x. I'm hoping those will clean things up for you.

    Ok, here is the result for 2.6.5-rc2 (3 times middle, with preemption),
    compared to 2.4.25.

    The result is, the performancedifference to 2.4.25 is the same as for
    2.6.4 as described above.
    Nearly means: The real processing time is about 1% faster than under
    2.6.4, but 8.3% slower than with 2.4.25. The system-processortime is 1.2%
    faster than under 2.6.4 but 31,7% more than under 2.4.25. The times for
    the user-processortime is unchanged.

    But I'm not shure if these values are really significant, because the
    values for the real time meassured each try differ a lot under 2.6.

    For example 2.6.5rc2:
    between 9.07 min and 8.37 min for real time.
    Under 2.4.25, the differences are a lot of smaller: between 8.06 min and
    8.15 min for real time.
    The values for user and system time are nearly constant with 6.49 min and
    36 sec (kernel 2.6) and 6.43 min / 27 sec for 2.4.25.


    Regards,
    Andreas Hartmann
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