linux-kernel - Re: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous snapshotting file system)

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: <20080821115310.GP8318@parisc-linux.org>
Date:	Thu, 21 Aug 2008 05:53:10 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Szabolcs Szakacsits <szaka@...s-3g.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	xfs@....sgi.com
Subject: Re: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous snapshotting file system)

On Thu, Aug 21, 2008 at 04:04:18PM +1000, Dave Chinner wrote:
> One thing I just found out - my old *laptop* is 4-5x faster than the
> 10krpm scsi disk behind an old cciss raid controller.  I'm wondering
> if the long delays in dispatch is caused by an interaction with CTQ
> but I can't change it on the cciss raid controllers. Are you using
> ctq/ncq on your machine?  If so, can you reduce the depth to
> something less than 4 and see what difference that makes?

I don't think that's going to make a difference when using CFQ.  I did
some tests that showed that CFQ would never issue more than one IO at a
time to a drive.  This was using sixteen userspace threads, each doing a
4k direct I/O to the same location.  When using noop, I would get 70k
IOPS and when using CFQ I'd get around 40k IOPS.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
--
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/