From 6b82021b9e91cd689fdffadbcdb9a42597bbe764 Mon Sep 17 00:00:00 2001 From: Mark Fasheh Date: Mon, 5 Apr 2010 18:17:14 -0700 Subject: 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 Also, I removed the OCFS2_DEFAULT_LOCAL_ALLOC_SIZE constant as it is no longer used and the comment above it was out of date.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 Signed-off-by: Joel Becker --- fs/ocfs2/ocfs2.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs/ocfs2/ocfs2.h') diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h index e98c954cf96..09d7aee3dab 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 */ -- cgit v1.2.3