Messages in this thread | | | Date | Thu, 26 Mar 2009 07:49:55 -0700 | From | Arjan van de Ven <> | Subject | Re: ext3 IO latency measurements (was: Linux 2.6.29) |
| |
On Thu, 26 Mar 2009 15:36:18 +0100 Jens Axboe <jens.axboe@oracle.com> wrote:
> On Thu, Mar 26 2009, Arjan van de Ven wrote: > > On Thu, 26 Mar 2009 12:08:15 +0100 > > Jens Axboe <jens.axboe@oracle.com> wrote: > > > > > > Did you capture the trace of the long delays in the read test > > > case? It can be two things, at least. One is that each little > > > read takes much longer than it should, the other is that we get > > > stuck waiting on a dirty page and hence that slows down the reads > > > a lot. > > > > > > > would be interesting to run latencytop during such runs... > > Things just drown in the noise in there sometimes, is my experience... > And disappear. Perhaps I'm just not very good at reading the output, > but it was never very useful for me. I know, not a very useful > complaint, I'll try and use it again and come up with something more > productive :-) > > But in this case, I bet it's also the atime updates. If Ingo turned > those off, the read results would likely be a lot better (and > consistent).
latencytop does identify those for sure. >
-- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org
| |