From: Martin Sustrik <sustrik@fastmq.com>
To: David Newall <davidn@davidnewall.com>
Cc: Martin Lucina <mato@kotelna.sk>, linux-kernel@vger.kernel.org
Subject: Re: Higher than expected disk write(2) latency
Date: Sun, 29 Jun 2008 13:34:18 +0200 [thread overview]
Message-ID: <4867733A.3060203@fastmq.com> (raw)
In-Reply-To: <48664F01.7060902@davidnewall.com>
David Newall wrote:
> Martin Lucina wrote:
>> Measurement of the write(2) time is performed using the TSC, so any
>> latency there is negligible.
>
> Measuring each write is lavish and bound to impact the results. To
> measure sustained throughput, get the time only at start and end, and
> divide the difference by the number of writes.
Hi,
We're using RDTSC to measure time, which takes ~30 nanoseconds to
complete. I would say this is negligible given that latency of a write
is 5 orders of magnitude higher.
Martin
next prev parent reply other threads:[~2008-06-29 12:03 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-28 12:11 Higher than expected disk write(2) latency Martin Lucina
2008-06-28 13:11 ` Roger Heflin
2008-06-30 18:10 ` Martin Sustrik
2008-06-30 19:02 ` Roger Heflin
2008-06-30 22:20 ` Martin Sustrik
2008-07-01 0:11 ` Bernd Eckenfels
2008-07-02 16:48 ` Martin Sustrik
2008-07-02 18:15 ` Jeff Moyer
2008-07-02 18:20 ` Martin Sustrik
2008-07-04 3:16 ` David Dillow
2008-07-02 21:33 ` Roger Heflin
2008-06-28 14:47 ` David Newall
2008-06-29 11:34 ` Martin Sustrik [this message]
2008-07-10 5:27 ` Andrew Morton
2008-07-10 8:12 ` Martin Sustrik
2008-07-10 8:14 ` Andrew Morton
2008-07-10 13:29 ` Chris Mason
2008-07-10 13:41 ` Martin Lucina
2008-07-10 14:01 ` Arjan van de Ven
2008-07-10 14:18 ` Chris Mason
2008-07-10 8:31 ` Alan Cox
2008-07-10 13:17 ` Martin Sustrik
2008-07-10 13:18 ` Andrew Morton
2008-07-11 15:17 ` Martin Sustrik
[not found] <fa.OZMA74BZPX46rhnjz1am4hB786M@ifi.uio.no>
2008-06-30 6:41 ` Robert Hancock
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