From: J. Eric Ivancich <ivancich@redhat.com>
Date: Thu, 23 Jul 2020 20:54:14 +0000 (-0400)
Subject: rgw: ordered list map efficiency
X-Git-Tag: v17.1.0~2021^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=0cfb4a51eff22cce1d8b4e8351101a2edf18dba9;p=ceph.git

rgw: ordered list map efficiency

Adding an object to the result map required two "find" operations
back-to-back, each of which was O(log n). By using
std::map::insert_or_assign function and getting an iterator, we can
avoid the second find.

Signed-off-by: J. Eric Ivancich <ivancich@redhat.com>
---

diff --git a/src/rgw/rgw_rados.cc b/src/rgw/rgw_rados.cc
index 441b56574f6..329e713fc32 100644
--- a/src/rgw/rgw_rados.cc
+++ b/src/rgw/rgw_rados.cc
@@ -8533,10 +8533,16 @@ int RGWRados::cls_bucket_list_ordered(const DoutPrefixProvider *dpp,
       ldpp_dout(dpp, 10) << "RGWRados::" << __func__ << ": got " <<
 	dirent.key << dendl;
 
-      m[name] = std::move(dirent);
-      last_entry_visited = &(m[name]);
-      ++count;
-    } else { // r == -ENOENT
+      auto [it, inserted] = m.insert_or_assign(name, std::move(dirent));
+      last_entry_visited = &it->second;
+      if (inserted) {
+	++count;
+      } else {
+	ldpp_dout(dpp, 0) << "WARNING: RGWRados::" << __func__ <<
+	  ": reassigned map value at \"" << name <<
+	  "\", which should not happen" << dendl;
+      }
+    } else {
       ldpp_dout(dpp, 10) << "RGWRados::" << __func__ << ": skipping " <<
 	dirent.key.name << "[" << dirent.key.instance << "]" << dendl;
       last_entry_visited = &tracker.dir_entry();