On Fri, 22 Aug 2008, Szabolcs Szakacsits wrote:

On Fri, 22 Aug 2008, Dave Chinner wrote:

quoted

On Thu, Aug 21, 2008 at 08:33:50PM +0300, Szabolcs Szakacsits wrote:

quoted

The 'nobarrier' mount option made a big improvement:

INteresting. Barriers make only a little difference on my laptop;
10-20% slower. But yes, barriers will have this effect on XFS.

If you've got NCQ, then you'd do better to turn off write caching
on the drive, turn off barriers and use NCQ to give you back the
performance that the write cache used to. That is, of course,
assuming the NCQ implementation doesn't suck....

Write cache off, nobarrier and AHCI NCQ lowered the XFS result:

                               MB/s    Runtime (s)
                              -----    -----------
  btrfs unstable              17.09        572
  ext3                        13.24        877
  btrfs 0.16                  12.33        793
  ntfs-3g unstable            11.52        673
  nilfs2 2nd+ runs            11.29        674
  reiserfs                     8.38        966
  xfs nobarrier                7.89        949
  nilfs2 1st run               4.95       3800
  xfs nobarrier, ncq, wc off   3.81       1973
  xfs                          1.88       3901

Retested with a different disk, SATA-II, NCQ, capable of 70-110 MB/s 
read/write:

                               MB/s    Runtime (s)
                              -----    -----------
  btrfs unstable, no dup      51.42        168
  btrfs unstable              42.67        197
  ext4 2.6.26                 35.63        245
  nilfs2 2nd+ runs            26.43        287
  ntfs-3g unstable            21.41        370
  ext3                        19.92        559
  xfs nobarrier               14.17        562
  reiserfs                    13.11        595
  nilfs2 1st run              12.06       3719
  xfs nobarrier, ncq, wc off   6.89       1070
  xfs                          1.95       3786

	Szaka

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