Messages in this thread | | | Date | Tue, 05 Jul 2005 01:25:33 +0200 | From | André Tomt <> | Subject | Re: [git patches] IDE update |
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Al Boldi wrote: > Bartlomiej Zolnierkiewicz wrote: { > >>>>On 7/4/05, Al Boldi <a1426z@gawab.com> wrote: >>>>Hdparm -tT gives 38mb/s in 2.4.31 >>>>Cat /dev/hda > /dev/null gives 2% user 33% sys 65% idle >>>> >>>>Hdparm -tT gives 28mb/s in 2.6.12 >>>>Cat /dev/hda > /dev/null gives 2% user 25% sys 0% idle 73% IOWAIT
The "hdparm doesn't get as high scores as in 2.4" is a old discussed to death "problem" on LKML. So far nobody has been able to show it affects anything but that pretty useless quasi-benchmark.
>>>>It feels like DMA is not being applied properly in 2.6.12. >>> >>>Same on 2.6.10,11,12. >>>No errors though, only sluggish system.
Really sluggish or just "benchmark-sluggish"? If the former, try selecting a different IO elevator/sheduler. If the latter it doesn't matter much, at least not with the very simple hdparm test :-)
>> >> What about earlier kernels? >> Please try to narrow down the problem to a specific kernel version. >> } > > Don't know about 2.6.0-2.6.9, but 2.4.31 is ok. > > Bartlomiej, > When you compare 2.4.31 with 2.6.12 don't you see this problem on your > machine? > If you have a fast system the slowdown won't show, but your IOWAIT will be > higher anyway!
Nothing wrong with 73% iowait, I'd even consider it very low while putting load on a harddrive. Its just time spent waiting for data to be returned from disk, and thus I usually expect no lower than ~98-99% while stressing any disk. Harddisks are _slow as snails_ compared to cpu cycles ;-)
Beware 2.4 didn't export that statistic at all to userspace, so 0% iowait gets reported from most 2.6-ready reporting tools on 2.4.
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