Jens Axboe wrote:
> On Tue, Jul 05 2005, Ondrej Zary wrote:
> 
>>Jens Axboe wrote:
>>
>>>On Tue, 2005-07-05 at 15:02 +0200, Ondrej Zary wrote:
>>>
>>>
>>>>>Ok, looks alright for both. Your machine is quite slow, perhaps that is
>>>>>showing the slower performance. Can you try and make HZ 100 in 2.6 and
>>>>>test again? 2.6.13-recent has it as a config option, otherwise edit
>>>>>include/asm/param.h appropriately.
>>>>>
>>>>
>>>>I forgot to write that my 2.6.12 kernel is already compiled with HZ 100 
>>>>(it makes the system more responsive).
>>>>I've just tried 2.6.8.1 with HZ 1000 and there is no difference in HDD 
>>>>performance comparing to 2.6.12.
>>>
>>>
>>>OK, interesting. You could try and boot with profile=2 and do
>>>
>>># readprofile -r
>>># dd if=/dev/hda of=/dev/null bs=128k 
>>># readprofile > prof_output
>>>
>>>for each kernel and post it here, so we can see if anything sticks out.
>>>
>>
>>Here are the profiles (used dd with count=4096) from 2.4.26 and 2.6.12 
>>(nothing from 2.6.8.1 because I don't have the .map file anymore).
> 
> 
> Looks interesting, 2.6 spends oodles of times copying to user space.
> Lets check if raw reads perform ok, please try and time this app in 2.4
> and 2.6 as well.
> 
> # gcc -Wall -O2 -o oread oread.c
> # time ./oread /dev/hda
> 
oread is faster than dd, but still not as fast as 2.4. In 2.6.12, HDD 
led is blinking, in 2.4 it's solid on during the read.

2.6.12:
root@pentium:/home/rainbow# time ./oread /dev/hda

real    0m25.082s
user    0m0.000s
sys     0m0.680s

2.4.26:
root@pentium:/home/rainbow# time ./oread /dev/hda

real    0m23.513s
user    0m0.000s
sys     0m2.360s

-- 
Ondrej Zary