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/suballoc.c b/fs/ocfs2/suballoc.c
index b7a065e..4c1399c 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -66,6 +66,7 @@
struct inode *alloc_inode,
struct buffer_head *bh,
u64 max_block,
+ u64 *last_alloc_group,
int flags);
static int ocfs2_cluster_group_search(struct inode *inode,
@@ -407,6 +408,7 @@
struct inode *alloc_inode,
struct buffer_head *bh,
u64 max_block,
+ u64 *last_alloc_group,
int flags)
{
int status, credits;
@@ -444,6 +446,11 @@
goto bail;
}
+ if (last_alloc_group && *last_alloc_group != 0) {
+ mlog(0, "use old allocation group %llu for block group alloc\n",
+ (unsigned long long)*last_alloc_group);
+ ac->ac_last_group = *last_alloc_group;
+ }
status = ocfs2_claim_clusters(osb,
handle,
ac,
@@ -518,6 +525,11 @@
alloc_inode->i_blocks = ocfs2_inode_sector_count(alloc_inode);
status = 0;
+
+ /* save the new last alloc group so that the caller can cache it. */
+ if (last_alloc_group)
+ *last_alloc_group = ac->ac_last_group;
+
bail:
if (handle)
ocfs2_commit_trans(osb, handle);
@@ -535,6 +547,7 @@
struct ocfs2_alloc_context *ac,
int type,
u32 slot,
+ u64 *last_alloc_group,
int flags)
{
int status;
@@ -600,7 +613,8 @@
}
status = ocfs2_block_group_alloc(osb, alloc_inode, bh,
- ac->ac_max_block, flags);
+ ac->ac_max_block,
+ last_alloc_group, flags);
if (status < 0) {
if (status != -ENOSPC)
mlog_errno(status);
@@ -644,7 +658,7 @@
status = ocfs2_reserve_suballoc_bits(osb, (*ac),
EXTENT_ALLOC_SYSTEM_INODE,
- slot, ALLOC_NEW_GROUP);
+ slot, NULL, ALLOC_NEW_GROUP);
if (status < 0) {
if (status != -ENOSPC)
mlog_errno(status);
@@ -690,7 +704,8 @@
status = ocfs2_reserve_suballoc_bits(osb, ac,
INODE_ALLOC_SYSTEM_INODE,
- slot, NOT_ALLOC_NEW_GROUP);
+ slot, NULL,
+ NOT_ALLOC_NEW_GROUP);
if (status >= 0) {
ocfs2_set_inode_steal_slot(osb, slot);
break;
@@ -707,6 +722,7 @@
{
int status;
s16 slot = ocfs2_get_inode_steal_slot(osb);
+ u64 alloc_group;
*ac = kzalloc(sizeof(struct ocfs2_alloc_context), GFP_KERNEL);
if (!(*ac)) {
@@ -742,14 +758,22 @@
goto inode_steal;
atomic_set(&osb->s_num_inodes_stolen, 0);
+ alloc_group = osb->osb_inode_alloc_group;
status = ocfs2_reserve_suballoc_bits(osb, *ac,
INODE_ALLOC_SYSTEM_INODE,
osb->slot_num,
+ &alloc_group,
ALLOC_NEW_GROUP |
ALLOC_GROUPS_FROM_GLOBAL);
if (status >= 0) {
status = 0;
+ spin_lock(&osb->osb_lock);
+ osb->osb_inode_alloc_group = alloc_group;
+ spin_unlock(&osb->osb_lock);
+ mlog(0, "after reservation, new allocation group is "
+ "%llu\n", (unsigned long long)alloc_group);
+
/*
* Some inodes must be freed by us, so try to allocate
* from our own next time.
@@ -796,7 +820,7 @@
status = ocfs2_reserve_suballoc_bits(osb, ac,
GLOBAL_BITMAP_SYSTEM_INODE,
- OCFS2_INVALID_SLOT,
+ OCFS2_INVALID_SLOT, NULL,
ALLOC_NEW_GROUP);
if (status < 0 && status != -ENOSPC) {
mlog_errno(status);