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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: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Andreas Gruenbacher 2010-08-16 19:05:23 +02:00 committed by Al Viro
parent 3b6036d148
commit 3a48ee8a4a
1 changed files with 23 additions and 5 deletions
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28
fs/mbcache.c
View File

@ -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;
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;
}