Performance monitoring?

[pll at lanminds.com]

(sorry for the delay in answering, I've been away from e-mail since 
 before Christmas :)

In a message dated: Fri, 20 Dec 2002 13:25:07 EST
bscott at ntisys.com said:

>On Fri, 20 Dec 2002, at 11:17am, gnhlug at sophic.org wrote:
>> Without all of that information, unless you can show that the system's I/O
>> requests exceeded the system's capacity to provide I/O during some time
>> period ...
>
>  But is Paul really looking for that kind of detail?  It sounds to me like
>Paul just wants to know how much time the *system* spends waiting for the
>disk (or disks).  Compare that to total system time, and you have a fair
>indication of whether the system is waiting on the disk a lot.  Maybe the
>system isn't waiting on the disk a lot, in which case, you look elsewhere
>for the cause of your performance problem.
>
>  (Paul, if I'm wrong in my assumptions about what you want, please say so.)

Nope, you're right on.

>  You could measure time spent waiting on the disk in the device driver
>fairly easily.

Yeah, but that would mean hacking kernel code, and I'd like to avoid 
that if possible. 

Ideally, you'd think that there would be some way to query the device 
and determine if it can respond to a request, some-what like 'ping' 
for devices.

>  Of course, I have no idea if Linux, or any of the disk device drivers,
>actually *do* this, but I wouldn't think it would be *that* hard.  Of
>course, I really don't have any idea what I am talking about, but that's
>never stopped me before.... ;-)

Ahh, we won't hold that against you :)
-- 

Seeya,
Paul
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