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

Dave Chinner
2008-08-21T06:03:18Z

On Thu, Aug 21, 2008 at 03:15:08PM +1000, Dave Chinner wrote:
> On Thu, Aug 21, 2008 at 05:46:00AM +0300, Szabolcs Szakacsits wrote:
> > On Thu, 21 Aug 2008, Dave Chinner wrote:
> > Everything is default.
> >
> > % rpm -qf =mkfs.xfs
> > xfsprogs-2.9.8-7.1
> >
> > which, according to ftp://oss.sgi.com/projects/xfs/cmd_tars, is the
> > latest stable mkfs.xfs. Its output is
> >
> > meta-data=/dev/sda8 isize=256 agcount=4, agsize=1221440 blks
> > = sectsz=512 attr=2
> > data = bsize=4096 blocks=4885760, imaxpct=25
> > = sunit=0 swidth=0 blks
> > naming =version 2 bsize=4096
> > log =internal log bsize=4096 blocks=2560, version=2
> > = sectsz=512 sunit=0 blks, lazy-count=0
> > realtime =none extsz=4096 blocks=0, rtextents=0
>
> Ok, I thought it might be the tiny log, but it didn't improve anything
> here when increased the log size, or the log buffer size.

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?

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com