On Tue, Jul 05 2005, Ondrej Zary wrote: > 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: > [EMAIL PROTECTED]:/home/rainbow# time ./oread /dev/hda > > real 0m25.082s > user 0m0.000s > sys 0m0.680s > > 2.4.26: > [EMAIL PROTECTED]:/home/rainbow# time ./oread /dev/hda > > real 0m23.513s > user 0m0.000s > sys 0m2.360s
Hmm, still not as fast, not so good. 2.6 shows more idle time than 2.4, about 20% more. I seem to remember Ken Chen saying that 2.6 direct io was still a little slower than 2.4, your really slow hardware could be showing this to a much greater effect. I'll try and play with this tomorrow! -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/