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authorMark Fasheh <mfasheh@suse.com>2010-04-05 18:17:14 -0700
committerJoel Becker <joel.becker@oracle.com>2010-05-05 18:18:07 -0700
commit6b82021b9e91cd689fdffadbcdb9a42597bbe764 (patch)
treeac4235e792e74a2e60a41e95d62965b7ed4b3232 /fs/ocfs2/ocfs2.h
parent73c8a80003d13be54e2309865030404441075182 (diff)
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ocfs2: increase the default size of local alloc windows
I have observed that the current size of 8M gives us pretty poor fragmentation on multi-threaded workloads which do lots of writes. Generally, I can increase the size of local alloc windows and observe a marked decrease in fragmentation, even up and beyond window sizes of 512 megabytes. This makes sense for a couple reasons - larger local alloc means more room for reservation windows. On multi-node workloads the larger local alloc helps as well because we don't have to do window slides as often. Also, I removed the OCFS2_DEFAULT_LOCAL_ALLOC_SIZE constant as it is no longer used and the comment above it was out of date. To test fragmentation, I used a workload which launched 4 threads that did 4k writes into a series of about 140 alternating files. With resv_level=2, and a 4k/4k file system I observed the following average fragmentation for various localalloc= parameters: localalloc= avg. fragmentation 8 48 32 16 64 10 120 7 On larger cluster sizes, the difference is more dramatic. The new default size top out at 256M, which we'll only get for cluster sizes of 32K and above. Signed-off-by: Mark Fasheh <mfasheh@suse.com> Signed-off-by: Joel Becker <joel.becker@oracle.com>
Diffstat (limited to 'fs/ocfs2/ocfs2.h')
-rw-r--r--fs/ocfs2/ocfs2.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index e98c954..09d7aee 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -342,6 +342,9 @@ struct ocfs2_super
*/
unsigned int local_alloc_bits;
unsigned int local_alloc_default_bits;
+ /* osb_clusters_at_boot can become stale! Do not trust it to
+ * be up to date. */
+ unsigned int osb_clusters_at_boot;
enum ocfs2_local_alloc_state local_alloc_state; /* protected
* by osb_lock */
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