lkml.org 
[lkml]   [2002]   [May]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC][PATCH] IO wait accounting
From
Date
Rik van Riel <riel@conectiva.com.br> writes:

> On Sun, 12 May 2002, Zlatko Calusic wrote:
>> Rik van Riel <riel@conectiva.com.br> writes:
>> >
>> > And should we measure read() waits as well as page faults or
>> > just page faults ?
>>
>> Definitely both.
>
> OK, I'll look at a way to implement these stats so that
> every IO wait counts as iowait time ... preferably in a
> way that doesn't touch the code in too many places ;)
>
>> Somewhere on the web was a nice document explaining
>> how Solaris measures iowait%, I read it few years ago and it was a
>> great stuff (quite nice explanation).
>>
>> I'll try to find it, as it could be helpful.
>
> Please, it would be useful to get our info compatible with
> theirs so sysadmins can read their statistics the same on
> both systems.
>

Yes, that would be nice. Anyway, finding the document I mentioned will
be much harder than I thought. Googling last 15 minutes didn't make
progress. But, I'll keep trying.

Anyway, here is how Aix defines it:

Average percentage of CPU time that the CPUs were idle during which
the system had an outstanding disk I/O request. This value may be
inflated if the actual number of I/O requesting threads is less than
the number of idling processors.

(http://support.bull.de/download/redbooks/Performance/OptimizingYourSystemPerformance.pdf)

Also, Sun has a nice collection of articles at
http://www.sun.com/sun-on-net/itworld/, and among them
http://www.sun.com/sun-on-net/itworld/UIR981001perf.html which speaks
about wait time, but I'm still searching for a more technical document...
--
Zlatko
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:22    [W:0.052 / U:0.352 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site