From: Kefu Chai <kchai@redhat.com>
Date: Sat, 6 Mar 2021 10:00:49 +0000 (+0800)
Subject: osd/Watch: use vector<> instead of list<>
X-Git-Tag: v17.1.0~2670^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=d4c94d2b50f9535ce847bbae3f4c5ebb3a0aa1b6;p=ceph.git

osd/Watch: use vector<> instead of list<>

there is no need to use a list<> here. and this change does not
change the encoding schema here. also, as a fact, the user of the
watch-notify feature is decoding the bufferlist like:

 std::map<std::pair<uint64_t,uint64_t>, bufferlist> reply_map;
 std::set<std::pair<uint64_t,uint64_t> > missed_map;
 decode(reply_map, reply_p);
 decode(missed_map, reply_p);

so, in this change, change list<> to vector<> for both smaller memory
footprint and for better readability.

Signed-off-by: Kefu Chai <kchai@redhat.com>
---

diff --git a/src/osd/Watch.cc b/src/osd/Watch.cc
index 78aae6e2d962..ca71620d0df3 100644
--- a/src/osd/Watch.cc
+++ b/src/osd/Watch.cc
@@ -193,10 +193,11 @@ void Notify::maybe_complete_notify()
     // prepare reply
     bufferlist bl;
     encode(notify_replies, bl);
-    list<pair<uint64_t,uint64_t> > missed;
-    for (auto p = watchers.begin(); p != watchers.end(); ++p) {
-      missed.push_back(make_pair((*p)->get_watcher_gid(),
-				 (*p)->get_cookie()));
+    vector<pair<uint64_t,uint64_t>> missed;
+    missed.reserve(watchers.size());
+    for (auto& watcher : watchers) {
+      missed.emplace_back(watcher->get_watcher_gid(),
+                          watcher->get_cookie());
     }
     encode(missed, bl);