os/bluestore: Prealloc memory avoid realloc in list_collection.

Signed-off-by: Jianpeng Ma <jianpeng.ma@intel.com>

diff --git a/src/os/bluestore/BlueStore.cc b/src/os/bluestore/BlueStore.cc
index 7a86d8ea83434e8f76fabfdc9b45a2f17d89a455..8ff2a209d8016e20d28b6b586b57847680d85583 100644 (file)
--- a/src/os/bluestore/BlueStore.cc
+++ b/src/os/bluestore/BlueStore.cc
@@ -7122,6 +7122,7 @@ int BlueStore::getattrs(
 int BlueStore::list_collections(vector<coll_t>& ls)
 {
   RWLock::RLocker l(coll_lock);
+  ls.reserve(coll_map.size());
   for (ceph::unordered_map<coll_t, CollectionRef>::iterator p = coll_map.begin();
        p != coll_map.end();
        ++p)