Re: Odd IDE performance drop 2.4 vs 2.6?

[Ondrej Zary]

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
> > > disabled. 
> >
> > 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

/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

/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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