Re: Very poor performance with 2.6.4

From: Andreas Hartmann
Date: Mon Mar 29 2004 - 14:37:10 EST

Chris Mason wrote:
On Mon, 2004-03-29 at 01:16, Andreas Hartmann wrote:
Andrew Morton wrote:
> Andreas Hartmann <andihartmann@xxxxxxxxxx> 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.

Andreas Hartmann
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