[PATCH] filesystem hashes: NUMA interleaving

The following patch modifies the dentry cache and inode cache to enable the
use of vmalloc to alleviate boottime memory allocation imbalances on NUMA
systems, utilizing flags to the alloc_large_system_hash routine in order to
centralize the enabling of this behavior.

In general, for each hash, we check at the early allocation point whether
hash distribution is enabled, and if so we defer allocation.  At the late
allocation point we perform the allocation if it was not earlier deferred. 
These late allocation points are the same points utilized prior to the
addition of alloc_large_system_hash to the kernel.
Signed-off-by: Brent Casavant <bcasavan@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/dcache.c

@@ -1574,6 +1574,12 @@ static void __init dcache_init_early(void)
 {
 	int loop;
 
+	/* If hashes are distributed across NUMA nodes, defer
+	 * hash allocation until vmalloc space is available.
+	 */
+	if (hashdist)
+		return;
+
 	dentry_hashtable =
 		alloc_large_system_hash("Dentry cache",
 					sizeof(struct hlist_head),
@@ -1590,6 +1596,8 @@ static void __init dcache_init_early(void)
 
 static void __init dcache_init(unsigned long mempages)
 {
+	int loop;
+
 	/* 
 	 * A constructor could be added for stable state like the lists,
 	 * but it is probably not worth it because of the cache nature
@@ -1602,6 +1610,23 @@ static void __init dcache_init(unsigned long mempages)
 					 NULL, NULL);
 	
 	set_shrinker(DEFAULT_SEEKS, shrink_dcache_memory);
+
+	/* Hash may have been set up in dcache_init_early */
+	if (!hashdist)
+		return;
+
+	dentry_hashtable =
+		alloc_large_system_hash("Dentry cache",
+					sizeof(struct hlist_head),
+					dhash_entries,
+					13,
+					0,
+					&d_hash_shift,
+					&d_hash_mask,
+					0);
+
+	for (loop = 0; loop < (1 << d_hash_shift); loop++)
+		INIT_HLIST_HEAD(&dentry_hashtable[loop]);
 }
 
 /* SLAB cache for __getname() consumers */

fs/inode.c

@@ -1328,6 +1328,12 @@ void __init inode_init_early(void)
 {
 	int loop;
 
+	/* If hashes are distributed across NUMA nodes, defer
+	 * hash allocation until vmalloc space is available.
+	 */
+	if (hashdist)
+		return;
+
 	inode_hashtable =
 		alloc_large_system_hash("Inode-cache",
 					sizeof(struct hlist_head),
@@ -1344,10 +1350,29 @@ void __init inode_init_early(void)
 
 void __init inode_init(unsigned long mempages)
 {
+	int loop;
+
 	/* inode slab cache */
 	inode_cachep = kmem_cache_create("inode_cache", sizeof(struct inode),
 				0, SLAB_PANIC, init_once, NULL);
 	set_shrinker(DEFAULT_SEEKS, shrink_icache_memory);
+
+	/* Hash may have been set up in inode_init_early */
+	if (!hashdist)
+		return;
+
+	inode_hashtable =
+		alloc_large_system_hash("Inode-cache",
+					sizeof(struct hlist_head),
+					ihash_entries,
+					14,
+					0,
+					&i_hash_shift,
+					&i_hash_mask,
+					0);
+
+	for (loop = 0; loop < (1 << i_hash_shift); loop++)
+		INIT_HLIST_HEAD(&inode_hashtable[loop]);
 }
 
 void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)