On Thu, May 15, 2003 at 03:35:05PM +0200, Olaf Fr?czyk wrote:
>
> With vanilla 2.4.20 it is the same as 2.4.20 with XFS. Load is about 5,
> CPU is about 90% idle. 'cat' takes about 3-5 % CPU.
>
> What is really strange, if I use 'dd' eg.:
> dd if=/dev/hda1 of=/dev/hdc1 bsize=1024 count=1000000
> there are NO freezes at all.
> The system works smoothly. Load is about 1.2.
> dd takes for some time 30% CPU and then until finishes about 0.2 % CPU.
> This is for radhat, vanilla and vanilla+XFS kernels.
>
> So it is not caused by XFS code. I'll take it to LKML.
>
> BTW, does somebody know why there is such strange difference between
> doing 'dd' and 'cat'?
>
> The copy speed is the same for 'dd' and 'cat': about 6.6 MB/sec
what happens if you use bs=4096 to dd ?
doing a strace of cat shows it appears to do read/writes in 4096 byte
blocks perhaps this is making a difference.
--
Ethan Benson
http://www.alaska.net/~erbenson/
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