linux-kernel - Re: Compact Flash performance...

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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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