remove global stats lock from item allocation

This doesn't reduce mutex contention much, if at all, for the global stats lock, but it does remove a handful of instructions from the alloc hot path, which is always worth doing. Previous commits possibly added a handful of instructions for the loop and for the bucket readlock trylock, but this is still faster than .14 for writes overall.
wokaokeji · Sep 3, 2012 · 67d7cfc · 67d7cfc
1 parent 1c94e12
commit 67d7cfc
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Showing 6 changed files with 29 additions and 18 deletions.
diff --git a/items.c b/items.c
@@ -138,14 +138,8 @@ item *do_item_alloc(char *key, const size_t nkey, const int flags,
         /* Expired or flushed */
         if ((search->exptime != 0 && search->exptime < current_time)
             || (search->time <= oldest_live && oldest_live <= current_time)) {
-            STATS_LOCK();
-            stats.reclaimed++;
-            STATS_UNLOCK();
             itemstats[id].reclaimed++;
             if ((search->it_flags & ITEM_FETCHED) == 0) {
-                STATS_LOCK();
-                stats.expired_unfetched++;
-                STATS_UNLOCK();
                 itemstats[id].expired_unfetched++;
             }
             it = search;
@@ -163,14 +157,8 @@ item *do_item_alloc(char *key, const size_t nkey, const int flags,
                 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.evictions++;
-                STATS_UNLOCK();
                 it = search;
                 slabs_adjust_mem_requested(it->slabs_clsid, ITEM_ntotal(it), ntotal);
                 do_item_unlink_nolock(it, hv);
@@ -436,6 +424,26 @@ void item_stats_evictions(uint64_t *evicted) {
     mutex_unlock(&cache_lock);
 }
 
+void do_item_stats_totals(ADD_STAT add_stats, void *c) {
+    itemstats_t totals;
+    memset(&totals, 0, sizeof(itemstats_t));
+    int i;
+    for (i = 0; i < LARGEST_ID; i++) {
+        totals.expired_unfetched += itemstats[i].expired_unfetched;
+        totals.evicted_unfetched += itemstats[i].evicted_unfetched;
+        totals.evicted += itemstats[i].evicted;
+        totals.reclaimed += itemstats[i].reclaimed;
+    }
+    APPEND_STAT("expired_unfetched", "%llu",
+                (unsigned long long)totals.expired_unfetched);
+    APPEND_STAT("evicted_unfetched", "%llu",
+                (unsigned long long)totals.evicted_unfetched);
+    APPEND_STAT("evictions", "%llu",
+                (unsigned long long)totals.evicted);
+    APPEND_STAT("reclaimed", "%llu",
+                (unsigned long long)totals.reclaimed);
+}
+
 void do_item_stats(ADD_STAT add_stats, void *c) {
     int i;
     for (i = 0; i < LARGEST_ID; i++) {

diff --git a/items.h b/items.h
@@ -16,6 +16,7 @@ int  do_item_replace(item *it, item *new_it, const uint32_t hv);
 /*@null@*/
 char *do_item_cachedump(const unsigned int slabs_clsid, const unsigned int limit, unsigned int *bytes);
 void do_item_stats(ADD_STAT add_stats, void *c);
+void do_item_stats_totals(ADD_STAT add_stats, void *c);
 /*@null@*/
 void do_item_stats_sizes(ADD_STAT add_stats, void *c);
 void do_item_flush_expired(void);

diff --git a/memcached.c b/memcached.c
@@ -2585,8 +2585,6 @@ static void server_stats(ADD_STAT add_stats, conn *c) {
     APPEND_STAT("hash_power_level", "%u", stats.hash_power_level);
     APPEND_STAT("hash_bytes", "%llu", (unsigned long long)stats.hash_bytes);
     APPEND_STAT("hash_is_expanding", "%u", stats.hash_is_expanding);
-    APPEND_STAT("expired_unfetched", "%llu", stats.expired_unfetched);
-    APPEND_STAT("evicted_unfetched", "%llu", stats.evicted_unfetched);
     if (settings.slab_reassign) {
         APPEND_STAT("slab_reassign_running", "%u", stats.slab_reassign_running);
         APPEND_STAT("slabs_moved", "%llu", stats.slabs_moved);

diff --git a/memcached.h b/memcached.h
@@ -533,6 +533,7 @@ int   item_link(item *it);
 void  item_remove(item *it);
 int   item_replace(item *it, item *new_it, const uint32_t hv);
 void  item_stats(ADD_STAT add_stats, void *c);
+void  item_stats_totals(ADD_STAT add_stats, void *c);
 void  item_stats_sizes(ADD_STAT add_stats, void *c);
 void  item_unlink(item *it);
 void  item_update(item *it);

diff --git a/slabs.c b/slabs.c
@@ -293,11 +293,8 @@ bool get_stats(const char *stat_type, int nkey, ADD_STAT add_stats, void *c) {
             APPEND_STAT("bytes", "%llu", (unsigned long long)stats.curr_bytes);
             APPEND_STAT("curr_items", "%u", stats.curr_items);
             APPEND_STAT("total_items", "%u", stats.total_items);
-            APPEND_STAT("evictions", "%llu",
-                        (unsigned long long)stats.evictions);
-            APPEND_STAT("reclaimed", "%llu",
-                        (unsigned long long)stats.reclaimed);
             STATS_UNLOCK();
+            item_stats_totals(add_stats, c);
         } else if (nz_strcmp(nkey, stat_type, "items") == 0) {
             item_stats(add_stats, c);
         } else if (nz_strcmp(nkey, stat_type, "slabs") == 0) {

diff --git a/thread.c b/thread.c
@@ -631,6 +631,12 @@ void  item_stats(ADD_STAT add_stats, void *c) {
     mutex_unlock(&cache_lock);
 }
 
+void  item_stats_totals(ADD_STAT add_stats, void *c) {
+    mutex_lock(&cache_lock);
+    do_item_stats_totals(add_stats, c);
+    mutex_unlock(&cache_lock);
+}
+
 /*
  * Dumps a list of objects of each size in 32-byte increments
  */