diff options
Diffstat (limited to 'items.c')
| -rw-r--r-- | items.c | 119 |
1 files changed, 67 insertions, 52 deletions
@@ -85,7 +85,9 @@ static size_t item_make_header(const uint8_t nkey, const int flags, const int nb } /*@null@*/ -item *do_item_alloc(char *key, const size_t nkey, const int flags, const rel_time_t exptime, const int nbytes) { +item *do_item_alloc(char *key, const size_t nkey, const int flags, + const rel_time_t exptime, const int nbytes, + const uint32_t cur_hv) { uint8_t nsuffix; item *it = NULL; char suffix[40]; @@ -100,13 +102,39 @@ item *do_item_alloc(char *key, const size_t nkey, const int flags, const rel_tim mutex_lock(&cache_lock); /* do a quick check if we have any expired items in the tail.. */ + int tries = 5; + int tried_alloc = 0; item *search; rel_time_t oldest_live = settings.oldest_live; search = tails[id]; - if (search != NULL && (refcount_incr(&search->refcount) == 2)) { + /* We walk up *only* for locked items. Never searching for expired. + * Waste of CPU for almost all deployments */ + for (; tries > 0 && search != NULL; tries--, search=search->prev) { + uint32_t hv = hash(ITEM_key(search), search->nkey, 0); + /* Attempt to hash item lock the "search" item. If locked, no + * other callers can incr the refcount + */ + if (hv != cur_hv && item_trylock(hv) != 0) + continue; + /* Now see if the item is refcount locked */ + if (refcount_incr(&search->refcount) != 2) { + refcount_decr(&search->refcount); + /* Old rare bug could cause a refcount leak. We haven't seen + * it in years, but we leave this code in to prevent failures + * just in case */ + if (search->time + TAIL_REPAIR_TIME < current_time) { + itemstats[id].tailrepairs++; + search->refcount = 1; + do_item_unlink_nolock(search, hv); + } + item_unlock(hv); + continue; + } + + /* Expired or flushed */ if ((search->exptime != 0 && search->exptime < current_time) - || (search->time <= oldest_live && oldest_live <= current_time)) { // dead by flush + || (search->time <= oldest_live && oldest_live <= current_time)) { STATS_LOCK(); stats.reclaimed++; STATS_UNLOCK(); @@ -119,68 +147,55 @@ item *do_item_alloc(char *key, const size_t nkey, const int flags, const rel_tim } it = search; slabs_adjust_mem_requested(it->slabs_clsid, ITEM_ntotal(it), ntotal); - do_item_unlink_nolock(it, hash(ITEM_key(it), it->nkey, 0)); + do_item_unlink_nolock(it, hv); /* Initialize the item block: */ it->slabs_clsid = 0; } else if ((it = slabs_alloc(ntotal, id)) == NULL) { + tried_alloc = 1; if (settings.evict_to_free == 0) { itemstats[id].outofmemory++; - mutex_unlock(&cache_lock); - return NULL; - } - itemstats[id].evicted++; - itemstats[id].evicted_time = current_time - search->time; - if (search->exptime != 0) - itemstats[id].evicted_nonzero++; - if ((search->it_flags & ITEM_FETCHED) == 0) { + } else { + itemstats[id].evicted++; + itemstats[id].evicted_time = current_time - search->time; + if (search->exptime != 0) + itemstats[id].evicted_nonzero++; + if ((search->it_flags & ITEM_FETCHED) == 0) { + STATS_LOCK(); + stats.evicted_unfetched++; + STATS_UNLOCK(); + itemstats[id].evicted_unfetched++; + } STATS_LOCK(); - stats.evicted_unfetched++; + stats.evictions++; STATS_UNLOCK(); - itemstats[id].evicted_unfetched++; + it = search; + slabs_adjust_mem_requested(it->slabs_clsid, ITEM_ntotal(it), ntotal); + do_item_unlink_nolock(it, hv); + /* Initialize the item block: */ + it->slabs_clsid = 0; + + /* If we've just evicted an item, and the automover is set to + * angry bird mode, attempt to rip memory into this slab class. + * TODO: Move valid object detection into a function, and on a + * "successful" memory pull, look behind and see if the next alloc + * would be an eviction. Then kick off the slab mover before the + * eviction happens. + */ + if (settings.slab_automove == 2) + slabs_reassign(-1, id); } - STATS_LOCK(); - stats.evictions++; - STATS_UNLOCK(); - it = search; - slabs_adjust_mem_requested(it->slabs_clsid, ITEM_ntotal(it), ntotal); - do_item_unlink_nolock(it, hash(ITEM_key(it), it->nkey, 0)); - /* Initialize the item block: */ - it->slabs_clsid = 0; - - /* If we've just evicted an item, and the automover is set to - * angry bird mode, attempt to rip memory into this slab class. - * TODO: Move valid object detection into a function, and on a - * "successful" memory pull, look behind and see if the next alloc - * would be an eviction. Then kick off the slab mover before the - * eviction happens. - */ - if (settings.slab_automove == 2) - slabs_reassign(-1, id); - } else { - refcount_decr(&search->refcount); } - } else { - /* If the LRU is empty or locked, attempt to allocate memory */ - it = slabs_alloc(ntotal, id); - if (search != NULL) - refcount_decr(&search->refcount); + + refcount_decr(&search->refcount); + item_unlock(hv); + break; } + if (!tried_alloc && (tries == 0 || search == NULL)) + it = slabs_alloc(ntotal, id); + if (it == NULL) { itemstats[id].outofmemory++; - /* Last ditch effort. There was a very rare bug which caused - * refcount leaks. We leave this just in case they ever happen again. - * We can reasonably assume no item can stay locked for more than - * three hours, so if we find one in the tail which is that old, - * free it anyway. - */ - if (search != NULL && - search->refcount != 2 && - search->time + TAIL_REPAIR_TIME < current_time) { - itemstats[id].tailrepairs++; - search->refcount = 1; - do_item_unlink_nolock(search, hash(ITEM_key(search), search->nkey, 0)); - } mutex_unlock(&cache_lock); return NULL; } |