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Commit 3a48ee8a authored by Andreas Gruenbacher's avatar Andreas Gruenbacher Committed by Al Viro
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mbcache: Limit the maximum number of cache entries 

Limit the maximum number of mb_cache entries depending on the number of
hash buckets: if the only limit to the number of cache entries is the
available memory the hash chains can grow very long, taking a long time
to search.

At least partially solves https://bugzilla.lustre.org/show_bug.cgi?id=22771

.

Signed-off-by: default avatarAndreas Gruenbacher <agruen@suse.de>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 3b6036d1

fs/mbcache.c

+24 −6
Original line number Diff line number Diff line
@@ -80,6 +80,7 @@ struct mb_cache { 
	struct list_head		c_cache_list;

	const char			*c_name;

	atomic_t			c_entry_count;

	int				c_max_entries;

	int				c_bucket_bits;

	struct kmem_cache		*c_entry_cache;

	struct list_head		*c_block_hash;
@@ -243,6 +244,12 @@ mb_cache_create(const char *name, int bucket_bits) 
	if (!cache->c_entry_cache)

		goto fail2;



	/*

	 * Set an upper limit on the number of cache entries so that the hash

	 * chains won't grow too long.

	 */

	cache->c_max_entries = bucket_count << 4;



	spin_lock(&mb_cache_spinlock);

	list_add(&cache->c_cache_list, &mb_cache_list);

	spin_unlock(&mb_cache_spinlock);
@@ -333,7 +340,6 @@ mb_cache_destroy(struct mb_cache *cache) 
	kfree(cache);

}





/*

 * mb_cache_entry_alloc()

 *
@@ -345,17 +351,29 @@ mb_cache_destroy(struct mb_cache *cache) 
struct mb_cache_entry *

mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)

{

	struct mb_cache_entry *ce;

	struct mb_cache_entry *ce = NULL;



	if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) {

		spin_lock(&mb_cache_spinlock);

		if (!list_empty(&mb_cache_lru_list)) {

			ce = list_entry(mb_cache_lru_list.next,

					struct mb_cache_entry, e_lru_list);

			list_del_init(&ce->e_lru_list);

			__mb_cache_entry_unhash(ce);

		}

		spin_unlock(&mb_cache_spinlock);

	}

	if (!ce) {

		ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);

	if (ce) {

		if (!ce)

			return NULL;

		atomic_inc(&cache->c_entry_count);

		INIT_LIST_HEAD(&ce->e_lru_list);

		INIT_LIST_HEAD(&ce->e_block_list);

		ce->e_cache = cache;

		ce->e_used = 1 + MB_CACHE_WRITER;

		ce->e_queued = 0;

	}

	ce->e_used = 1 + MB_CACHE_WRITER;

	return ce;

}