[XFS] On machines with more than 8 cpus, when running parallel I/O

threads, the incore superblock lock becomes the limiting factor for
buffered write throughput. Make the contended fields in the incore
superblock use per-cpu counters so that there is no global lock to limit
scalability.

SGI-PV: 946630
SGI-Modid: xfs-linux-melb:xfs-kern:25106a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_linux.h b/fs/xfs/linux-2.6/xfs_linux.h
index 67389b745526..377a9f54a049 100644
--- a/fs/xfs/linux-2.6/xfs_linux.h
+++ b/fs/xfs/linux-2.6/xfs_linux.h
@@ -100,6 +100,11 @@
  */
 #undef  HAVE_REFCACHE   /* reference cache not needed for NFS in 2.6 */
 #define HAVE_SENDFILE   /* sendfile(2) exists in 2.6, but not in 2.4 */
+#if CONFIG_SMP
+#define HAVE_PERCPU_SB  /* per cpu superblock counters are a 2.6 feature */
+#else
+#undef  HAVE_PERCPU_SB  /* per cpu superblock counters are a 2.6 feature */
+#endif
 
 /*
  * State flag for unwritten extent buffers.