Re: 2.6.4 : 100% CPU use on EIDE disk operarion, VIA chipset

[Andreas Hartmann <andihartmann@freenet.de>]

Mikhail Ramendik wrote:
> Hello,
> 
> I have an computer with an AMD Duron, and the motehrboard chipset is VIA
> KT133. The hard drive is a Seagate Barracuda 7200.7 ; no other EIDE
> devices are attached.
> 
> I run an RH9-based distro, and added a 2.6.4 kernel to it. The following
> problem was tested with two kernel variants: 2.6.4+wolk2/0 with
> preeemption enabled, and 2.6.4 plain from kernel.org with preemption
> disabled. No difference.
> 
> I noticed performance problems with 2.6.4, and tracked them to strange
> HDD behavior.
> 
> It turned out that on disk-intensive operation, the "system" CPU usage
> skyrockets. With a mere "cp" of a large file to the same direstory
> (tested with ext3fs and FAT32 file systems), it is 100% practically all
> of the time !

Which tool do you use for measure? xosview?

I'm having here the same problem. But it depends on the tool which is used 
for measuring. If I use top from procps 3.2, I can't see this high system 
load. "time" can't see it, too.

This is what top says during cp of 512MB-file:
Cpu(s):  2.0% us,  8.3% sy,  0.0% ni,  0.0% id, 89.0% wa,  0.7% hi,  0.0% si

New is "wa", what probably means "wait". This value is very high as long 
as the HD is writing or reading datas:

cp dummy /dev/null
produces this top-line:
Cpu(s):  3.0% us,  5.3% sy,  0.0% ni,  0.0% id, 91.0% wa,  0.7% hi,  0.0% si

and time says:
real    0m53.195s
user    0m0.013s
sys     0m2.124s


But you're right, 2.6.4 is slower than 2.4.25. See the thread "Very poor 
performance with 2.6.4" here in the list.


Regards,
Andreas Hartmann