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Message-id: <465F618C.1020200@shaw.ca>
Date: Thu, 31 May 2007 18:00:12 -0600
From: Robert Hancock <hancockr@...w.ca>
To: Jeff Garzik <jeff@...zik.org>
Cc: Mark Lord <liml@....ca>,
Daniel J Blueman <daniel.blueman@...il.com>,
bzolnier@...il.com, linux-ide@...r.kernel.org,
Linux Kernel <linux-kernel@...r.kernel.org>,
Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: Compact Flash performance...
Jeff Garzik wrote:
> Mark Lord wrote:
>> To maximize throughput, some kind of host-queuing would be needed,
>> or just have the driver sit in a tight loop, starting the next I/O
>> immediately when the previous one finishes. Linux isn't that quick
>> (yet).
>
>
> I was talking on IRC with Tejun just recently. There are several
> controllers (and/or "situations") like this, where some amount of host
> queueing would permit greater throughput, even when NCQ is not
> supported. sata_sx4 is the most dramatic example, where host queueing
> could potentially increase speed by a factor of 10 or more, since it is
> penalized by an awful two-irq-per-command (w/ a per-host bottleneck to
> boot) setup. Silicon Image has a "command buffer". And overall, I
> designed ->qc_prep() hook separate from ->qc_issue() to enable the
> prepartion of multiple commands such that it only takes a simple "go"
> I/O to start a transaction, immediately after the previous one ends.
>
> Jeff
Theoretically NVIDIA nForce4 ADMA could likely do this as well, as it
seems to allow chaining up multiple commands to execute in succession
(assuming they're not NCQ)..
--
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/
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