linux-kernel - Re: Why is NCQ enabled by default by libata? (2.6.20)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <460BF73C.5070707@cfl.rr.com>
Date:	Thu, 29 Mar 2007 13:28:28 -0400
From:	Phillip Susi <psusi@....rr.com>
To:	Jeff Garzik <jeff@...zik.org>
CC:	Justin Piszcz <jpiszcz@...idpixels.com>, linux@...izon.com,
	htejun@...il.com, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Why is NCQ enabled by default by libata? (2.6.20)

Jeff Garzik wrote:
> 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.

But when writing, what is the difference between queuing multiple tagged 
writes, and sending down multiple untagged cached writes that complete 
immediately and actually hit the disk later?  Either way the host keeps 
sending writes to the disk until it's buffers are full, and the disk is 
constantly trying to commit those buffers to the media in the most 
optimal order.


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/