From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: "Martin A. Fink" <fink@mpe.mpg.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: SATA-performance: Linux vs. FreeBSD
Date: Mon, 12 Feb 2007 19:19:06 +0100 [thread overview]
Message-ID: <45D0AF9A.509@s5r6.in-berlin.de> (raw)
In-Reply-To: <200702121737.12882.fink@mpe.mpg.de>
Martin A. Fink wrote:
> This means, that the CPU is only 7.3 of 52.8 seconds working.
...
> It looks like
> the SATA driver simply blocks the CPU while doing whatever...
The system sleeps while waiting for the disk (actually, for the SATA
host port) to be done with its work.
As Andi explained, if the system gives the disk a small task, waits for
the task to be completed, then gives it a next task and so on, latencies
add up and eat into effective bandwidth. Give the disk a whole set of
tasks so that
- it has immediately something new to do when it finished one task,
- deep pipes are not mostly empty due to "bubbles" in the pipe,
- tasks can be reordered to be executed in optimized manner for good
bandwidth utilization (if software/ firmware/ hardware is present
which supports this; e.g. the Linux kernel itself),
etc.
Also make each task large so that the ratio of protocol overhead to net
data payload stays minimal.
--
Stefan Richter
-=====-=-=== --=- -==--
http://arcgraph.de/sr/
next prev parent reply other threads:[~2007-02-12 18:19 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-12 14:02 SATA-performance: Linux vs. FreeBSD Martin A. Fink
2007-02-12 17:04 ` Andi Kleen
2007-02-12 16:27 ` Martin A. Fink
2007-02-12 18:41 ` Andi Kleen
2007-02-12 17:56 ` Martin A. Fink
2007-02-12 18:17 ` Ray Lee
2007-02-12 19:08 ` Alan
2007-02-12 20:34 ` Nigel Cunningham
2007-02-13 9:34 ` Martin A. Fink
2007-02-13 11:25 ` Alan
2007-02-13 12:32 ` Martin A. Fink
2007-02-13 14:47 ` Theodore Tso
2007-02-13 15:03 ` Alan
2007-02-13 17:12 ` Jeff Garzik
2007-02-12 23:31 ` Matthias Schniedermeyer
2007-02-13 9:25 ` Martin A. Fink
2007-02-13 10:08 ` Arjan van de Ven
2007-02-13 11:18 ` Andi Kleen
2007-02-13 10:25 ` Arjan van de Ven
2007-02-13 11:27 ` Alan
2007-02-13 11:59 ` Jörn Engel
2007-02-13 19:54 ` Jeffrey Hundstad
2007-02-13 10:16 ` Matthias Schniedermeyer
2007-02-13 10:29 ` Martin A. Fink
2007-02-13 12:04 ` Jörn Engel
2007-02-13 12:24 ` Matthias Schniedermeyer
2007-02-13 12:49 ` Martin A. Fink
2007-02-13 13:53 ` Matthias Schniedermeyer
2007-02-12 16:37 ` Martin A. Fink
2007-02-12 18:19 ` Stefan Richter [this message]
2007-02-13 19:09 ` Jeff Carr
2007-02-12 17:42 ` Martin A. Fink
2007-02-15 5:48 ` Tejun Heo
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