Re: 2.6.21.1 - 97% wait time on IDE operations

[Paolo Ornati <ornati@fastwebnet.it>]

On Sat, 26 May 2007 15:05:38 +0200
Tommy Vercetti <vercetti@zlew.org> wrote:

> I was trying to get answer to my question around, but no one knows.
> I do have DMA turned on, etc, yet - on extensive harddrive operations wait 
> time is 90+% , which means that machine is waiting, rather than doing 
> something meanwhile. (I guess). 
> Can someone describe to me , in more detail why is that happening, and what 
> steps should I consider to avoid it ? I couldn't find any answers that would 
> have help me on net.

It means that the disk is slow and the CPU is fast... so while the disk
is busy seeking and reading data the CPU has nothing to do but wait for
it.

Idle == CPU has nothing to do
Waiting == CPU has nothing to do, but it will have as soon as the slow
	disk (or whatever) delivers data


Anyway 97% is quite high... what CPU / Hard Disk do you have?

What kernel version?
I/O scheduler? (cat /sys/block/DEVICE/queue/scheduler)
Filesystem?

And what time of "operations" are you doing?

-- 
	Paolo Ornati
	Linux 2.6.22-rc3-cfs-v14-gf193016a on x86_64