[Gllug] Poor disk performance - help

[Ashley Evans]

First you could try checking if DMA is enabled, hdparm -d /dev/hda

-d 1 will try to enable it.

Most kernels come with the "use dma by default" turned on so if dma isn't 
enabled you may find the kernel you're using doesn't support the chipset of 
your motherboard fully. Look up the chipset on google and you're sure to find 
out.

Ashley

On Sunday 21 March 2004 22:44, Alain Williams wrote:
> Hi,
>
> I have just replaced my motherboard & CPU - but disk I/O is abysmal.
> I have AMD Athlon XP 3000+ running at 2166 MHz, I have 1G ddr 333MHz RAM.
> Soltek motherboard (SLKT600-RL).
> I have IDE 2 disks & 2 CDs.
>
> Machine seems OK except that disk i/o is slooow and uses vast amounts of
> CPU, I first noticed it when a ftp from a local machine was ~2Mbyte/sec
> with 50->100% cpu, I would expect ~10MB/sec.
>
> If I do a disk read:
> 	# time dd if=/dev/hda10 of=/dev/null bs=1M count=100
> 	100+0 records in
> 	100+0 records out
>
> 	real    0m12.903s
> 	user    0m0.010s
> 	sys     0m11.380s
>
> Note the high system time. It doesn't seem to be the machine in general as
> if I immediately repeat (ie from buffer cache) I get:
>
> 	# time dd if=/dev/hda10 of=/dev/null bs=1M count=100
> 	100+0 records in
> 	100+0 records out
>
> 	real    0m0.324s
> 	user    0m0.000s
> 	sys     0m0.270s
>
> If I do this on what should be a much slower machine (1GHz Duron, 512Mb
> RAM) I get:
>
> 	# time dd if=/dev/hda2 of=/dev/null bs=1M count=100
> 	100+0 records in
> 	100+0 records out
>
> 	real    0m3.512s
> 	user    0m0.000s
> 	sys     0m0.930s
>
> Note that the system time is a much smaller fraction of the real time.
>
> (You can see that it is slower as if I immediately repeat:
> 	# time dd if=/dev/hda2 of=/dev/null bs=1M count=100
> 	100+0 records in
> 	100+0 records out
>
> 	real    0m0.646s
> 	user    0m0.000s
> 	sys     0m0.640s
> )
>
>
> OK, so I have got something screwed - but what, any idea where I should
> start looking ?
>
>
> --
> Alain Williams
>
> #include <std_disclaimer.h>
>
> FATHERS-4-JUSTICE - Campaigning for equal rights for parents and the
> best interests of our children. See http://www.fathers-4-justice.org
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