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SubjectRe: Odd IDE performance drop 2.4 vs 2.6?
Alan Cox wrote:
> On Llu, 2005-06-13 at 15:06, Nick Piggin wrote:
>>>Make sure you have pre-empt disabled and the antcipatory I/O scheduler
>>I don't think that those could explain it.
> Try it and see. The anticipatory I/O scheduler does horrible things to
> my IDE streaming performance numbers and to swap performance. It tries
> to merge I/O by delaying it which is deeply ungood when it comes to IDE
> streaming even if its good for general I/O.

Changing the scheduler did not help (the results are about the same with
any of the 4 schedulers). Read ahead is already set to 256 (increasing
to 1024 did not help either). Kernel compilation takes too much time
here so I didn't test with preempt disabled.
The drive is WD300BB (7200RPM) in UDMA2 mode.

root@pentium:~# cat /sys/block/hda/queue/scheduler
noop anticipatory [deadline] cfq
root@pentium:~# hdparm -tT /dev/hda

Timing cached reads: 176 MB in 2.00 seconds = 88.00 MB/sec
Timing buffered disk reads: 34 MB in 3.02 seconds = 11.26 MB/sec
root@pentium:~# hdparm /dev/hda

multcount = 16 (on)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 1 (on)
readonly = 0 (off)
readahead = 256 (on)
geometry = 58168/16/63, sectors = 58633344, start = 0

Ondrej Zary
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