ocfs2: Optimize inode group allocation by recording last used group.
In ocfs2, the block group search looks for the "emptiest" group
to allocate from. So if the allocator has many equally(or almost
equally) empty groups, new block group will tend to get spread
out amongst them.
So we add osb_inode_alloc_group in ocfs2_super to record the last
used inode allocation group.
For more details, please see
http://oss.oracle.com/osswiki/OCFS2/DesignDocs/InodeAllocationStrategy.
I have done some basic test and the results are a ten times improvement on
some cold-cache stat workloads.
Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index e1844d5..b65d19c 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -343,6 +343,9 @@
unsigned int osb_dx_mask;
u32 osb_dx_seed[4];
+
+ /* the group we used to allocate inodes. */
+ u64 osb_inode_alloc_group;
};
#define OCFS2_SB(sb) ((struct ocfs2_super *)(sb)->s_fs_info)