[mesos] 03/03: Reserved vector capacities within Master::offer.

[bm...@apache.org]

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bmahler pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/mesos.git

commit 82dbbc9d90079fd5134a28377e21669b2f41980e
Author: Benjamin Mahler <bm...@apache.org>
AuthorDate: Wed Sep 5 14:51:39 2018 -0700

    Reserved vector capacities within Master::offer.
    
    Review: https://reviews.apache.org/r/68636
---
 src/master/master.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/master/master.cpp b/src/master/master.cpp
index 9179cf3..3277b57 100644
--- a/src/master/master.cpp
+++ b/src/master/master.cpp
@@ -9245,13 +9245,20 @@ void Master::offer(
     return;
   }
 
+  size_t offersEstimate = 0u;
+  foreachvalue (const auto& agents, resources) {
+    offersEstimate += agents.size();
+  }
 
   // Each offer we create is tied to a single agent
   // and a single allocation role.
   ResourceOffersMessage message;
+  message.mutable_offers()->Reserve(offersEstimate);
+  message.mutable_pids()->Reserve(offersEstimate);
 
   // We keep track of the offer IDs so that we can log them.
   vector<OfferID> offerIds;
+  offerIds.reserve(offersEstimate);
 
   foreachkey (const string& role, resources) {
     foreachpair (const SlaveID& slaveId,