From: Jens Axboe <axboe@kernel.dk>
To: Edoardo Comar <ECOMAR@uk.ibm.com>
Cc: fio@vger.kernel.org
Subject: Re: latency measurements when adding thinktime
Date: Fri, 17 May 2013 12:43:05 +0200 [thread overview]
Message-ID: <20130517104305.GW697@kernel.dk> (raw)
In-Reply-To: <20130517102244.GV697@kernel.dk>
On Fri, May 17 2013, Jens Axboe wrote:
> On Fri, May 17 2013, Edoardo Comar wrote:
> > Hi Jens,
> >
> > thanks a lot, I tried your suggestion straight away:
> > The cpu line in the output shows that the job has not been idle at all.
> > but even with thinktime_spin, the latency stays high at at 150ms.
> >
> > Note also that if I increase thinktime & thinktime_spin by another 10000
> > us
> > to a total of 20000, then the reported latency goes up another 150ms to a
> > total of 300ms.
> > Could this be a bug?
>
> It certainly could. Let me take a look here and see if I can reproduce
> it.
And it was... Basically the same issue that was fixed for rate limiting.
When going to sleep or spinning, ensure that we have all IOs flushed.
Otherwise we could unfairly attribute the sleep towards the completion
latencies.
Fixed here:
http://git.kernel.dk/?p=fio.git;a=commit;h=002e7183cb86d6100efef690b6fa90bf0988b084
or just git pull and you'll get the fix.
--
Jens Axboe
next prev parent reply other threads:[~2013-05-17 10:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-17 0:00 latency measurements when adding thinktime Edoardo Comar
2013-05-17 7:47 ` Jens Axboe
2013-05-17 9:24 ` Edoardo Comar
2013-05-17 10:22 ` Jens Axboe
2013-05-17 10:38 ` Edoardo Comar
2013-05-17 10:43 ` Jens Axboe [this message]
2013-05-17 10:48 ` Edoardo Comar
2013-05-17 10:50 ` Jens Axboe
2013-05-17 10:48 ` Jens Axboe
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