From: Jeff Garzik <jeff@garzik.org>
To: Phillip Susi <psusi@cfl.rr.com>
Cc: Justin Piszcz <jpiszcz@lucidpixels.com>,
linux@horizon.com, htejun@gmail.com, linux-ide@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: Why is NCQ enabled by default by libata? (2.6.20)
Date: Wed, 28 Mar 2007 10:48:51 -0400 [thread overview]
Message-ID: <460A8053.3040209@garzik.org> (raw)
In-Reply-To: <460A7EE7.5070101@cfl.rr.com>
Phillip Susi wrote:
> Justin Piszcz wrote:
>> I would try with write-caching enabled.
>> Also, the RAID5/RAID10 you mention seems like each volume is on part of
>> the platter, a strange setup you got there :)
>
> Shouldn't NCQ only help write performance if write caching is
> _disabled_? Since write cache essentially is just non tagged command
> queuing?
NCQ provides for a more asynchronous flow. It helps greatly with reads
(of which most are, by nature, synchronous at the app level) from
multiple threads or apps. It helps with writes, even with write cache
on, by allowing multiple commands to be submitted and/or retired at the
same time.
Jeff
next prev parent reply other threads:[~2007-03-28 14:49 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-27 16:16 Why is NCQ enabled by default by libata? (2.6.20) linux
2007-03-27 16:25 ` Justin Piszcz
2007-03-27 16:41 ` linux
2007-03-27 16:44 ` Justin Piszcz
2007-03-27 16:58 ` linux
2007-03-27 17:03 ` Justin Piszcz
2007-03-28 14:42 ` Phillip Susi
2007-03-28 14:48 ` Jeff Garzik [this message]
2007-03-28 15:22 ` Andy Warner
2007-03-29 17:28 ` Phillip Susi
2007-03-29 18:40 ` linux
2007-03-29 18:51 ` Jeff Garzik
2007-03-29 21:35 ` Alan Cox
[not found] <Pine.LNX.4.64.0703241232580.11608@p34.internal.lan>
2007-03-27 5:59 ` Jeff Garzik
2007-03-27 14:26 ` Mark Lord
2007-03-27 18:18 ` Mark Rustad
2007-03-27 18:38 ` Jeff Garzik
2007-03-27 22:12 ` Mark Rustad
2007-03-31 12:55 ` Ric Wheeler
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