From cc7ec3e18d191575c4d94d6f188cada800f51f72 Mon Sep 17 00:00:00 2001
From: Jason Dillaman <dillaman@redhat.com>
Date: Wed, 8 May 2019 14:09:17 -0400
Subject: [PATCH] common/Finisher: avoid memory re-allocations for finisher
 queue

Since there is only a single thread associated with the Finisher,
swap between two queues to avoid the need to re-allocate a new
vector for each iteration through the loop. Also replace the
condition broadcast with a signal since there is only a single
thread to wake up.

Signed-off-by: Jason Dillaman <dillaman@redhat.com>
---
 src/common/Finisher.cc | 14 +++++++-------
 src/common/Finisher.h  |  8 +++++---
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/src/common/Finisher.cc b/src/common/Finisher.cc
index 277fe06f197..974241f5719 100644
--- a/src/common/Finisher.cc
+++ b/src/common/Finisher.cc
@@ -51,23 +51,23 @@ void *Finisher::finisher_thread_entry()
       // To reduce lock contention, we swap out the queue to process.
       // This way other threads can submit new contexts to complete
       // while we are working.
-      vector<pair<Context*,int>> ls;
-      ls.swap(finisher_queue);
+      in_progress_queue.swap(finisher_queue);
       finisher_running = true;
       ul.unlock();
-      ldout(cct, 10) << "finisher_thread doing " << ls << dendl;
+      ldout(cct, 10) << "finisher_thread doing " << in_progress_queue << dendl;
 
       if (logger) {
 	start = ceph_clock_now();
-	count = ls.size();
+	count = in_progress_queue.size();
       }
 
       // Now actually process the contexts.
-      for (auto p : ls) {
+      for (auto p : in_progress_queue) {
 	p.first->complete(p.second);
       }
-      ldout(cct, 10) << "finisher_thread done with " << ls << dendl;
-      ls.clear();
+      ldout(cct, 10) << "finisher_thread done with " << in_progress_queue
+                     << dendl;
+      in_progress_queue.clear();
       if (logger) {
 	logger->dec(l_finisher_queue_len, count);
 	logger->tinc(l_finisher_complete_lat, ceph_clock_now() - start);
diff --git a/src/common/Finisher.h b/src/common/Finisher.h
index b70b600af6c..6926d8207b4 100644
--- a/src/common/Finisher.h
+++ b/src/common/Finisher.h
@@ -47,6 +47,7 @@ class Finisher {
 
   /// Queue for contexts for which complete(0) will be called.
   std::vector<std::pair<Context*,int>> finisher_queue;
+  std::vector<std::pair<Context*,int>> in_progress_queue;
 
   std::string thread_name;
 
@@ -66,10 +67,11 @@ class Finisher {
   /// Add a context to complete, optionally specifying a parameter for the complete function.
   void queue(Context *c, int r = 0) {
     std::unique_lock ul(finisher_lock);
-    if (finisher_queue.empty()) {
-      finisher_cond.notify_all();
-    }
+    bool was_empty = finisher_queue.empty();
     finisher_queue.push_back(std::make_pair(c, r));
+    if (was_empty) {
+      finisher_cond.notify_one();
+    }
     if (logger)
       logger->inc(l_finisher_queue_len);
   }
-- 
2.39.5