From: Bruce Cran <bruce@cran.org.uk>
To: "Jeffrey McVay (jmcvay)" <jmcvay@micron.com>
Cc: Jens Axboe <axboe@kernel.dk>,
"fio@vger.kernel.org" <fio@vger.kernel.org>
Subject: Re: FIO 2.0.9 for Windows Server 2008 RC1 SP2 reports extreme latencies
Date: Wed, 10 Oct 2012 11:07:58 +0100 [thread overview]
Message-ID: <507548FE.9010106@cran.org.uk> (raw)
In-Reply-To: <C8CA972100601A41AE302914E9CE194655F9DEF4@NTXBOIMBX03.micron.com>
On 06/10/2012 01:25, Jeffrey McVay (jmcvay) wrote:
> Anything new on this issue? There is a reviewer using FIO on Windows to measure latency values. I am concerned that they may publish inaccurate data.
I'm working on it again today.
The problem is that windowsaio iterates over the list of outstanding IOs
(busylist), but that list has the most recent first. The sequence of
queue/dequeue with an iodepth of 4 is:
queue 1
queue 2
queue 3
queue 4
dequeue 4
queue 5
dequeue 5
queue 6
dequeue 6
dequeue 3
dequeue 2
dequeue 1
So the first IO therefore has an apparent latency equal to the runtime
of fio.
--
Bruce Cran
next prev parent reply other threads:[~2012-10-10 10:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-24 5:41 FIO 2.0.9 for Windows Server 2008 RC1 SP2 reports extreme latencies Jeffrey McVay (jmcvay)
2012-09-24 13:28 ` Bruce Cran
2012-09-26 16:30 ` Jeffrey McVay (jmcvay)
2012-09-26 16:32 ` Bruce Cran
2012-09-29 6:23 ` Jens Axboe
2012-09-29 13:46 ` Bruce Cran
2012-09-29 14:21 ` Jens Axboe
2012-10-06 0:25 ` Jeffrey McVay (jmcvay)
2012-10-10 10:07 ` Bruce Cran [this message]
2012-10-10 10:41 ` Bruce Cran
2012-10-10 14:15 ` Jens Axboe
2012-10-10 14:18 ` Bruce Cran
2012-10-10 14:19 ` Jens Axboe
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