linux-kernel - Re: high system cpu load during intense disk i/o

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Date:	Tue, 7 Aug 2007 12:43:51 +0300
From:	Dimitrios Apostolou <jimis@....net>
To:	Rafał Bilski <rafalbilski@...eria.pl>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: high system cpu load during intense disk i/o

On Tuesday 07 August 2007 12:03:28 Rafał Bilski wrote:
> >> Just tested (plain curiosity).
> >> via82cxxx average result @533MHz:
> >> /dev/hda:
> >> Timing cached reads:   232 MB in  2.00 seconds = 115.93 MB/sec
> >> Timing buffered disk reads:   64 MB in  3.12 seconds =  20.54 MB/sec
> >> pata_via average result @533MHz:
> >> /dev/sda:
> >> Timing cached reads:   234 MB in  2.01 seconds = 116.27 MB/sec
> >> Timing buffered disk reads:   82 MB in  3.05 seconds =  26.92 MB/sec
> >
> > Interesting! I haven't tried libata myself on that system, I only have
> > remote access to it so I'm a bit afraid...
>
> Just change root=/dev/hda1 to append="root=/dev/sda1" in lilo.conf.
> And change fstab. If You don't change "/" then system will go into single
> user mode after reboot.
>
> > Rafal, I hope that system you run hdparm on isn't the archlinux one! Is
> > it easy to load an old kernel (even two years old) and do the same test?
> > If it is, please let me know of the results.
>
> I don't think it is possible. If I remember right kernel can't be older
> then glibc kernel headers.
> Btw. My disk is 20GB 2,5" ATA33. I wonder how 26MB/s is possible. I don't
> expect more.

Aha! So perhaps libata gives even greater performance benefit for better 
drives. I'll try to get local access to my PC and try it. Thanks. 


Dimitris

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