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: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/mbcache.c b/fs/mbcache.c
index cf4e6cd..9344474 100644
--- a/fs/mbcache.c
+++ b/fs/mbcache.c
@@ -80,6 +80,7 @@
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 @@
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 @@
kfree(cache);
}
-
/*
* mb_cache_entry_alloc()
*
@@ -345,17 +351,29 @@
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;
- ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
- if (ce) {
+ 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)
+ 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;
}