Al Boldi wrote:
Bartlomiej Zolnierkiewicz wrote: {
On 7/4/05, Al Boldi <[email protected]> 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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