From 4a080eb008a71c374dc2b12666dac9d8aab76b99 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@cloudius-systems.com>
Date: Mon, 6 Oct 2014 21:30:49 +0300
Subject: [PATCH] core: switch to spsc_queue for interthread communication

It's much faster than a normal queue.
---
 core/reactor.cc | 4 ++--
 core/reactor.hh | 8 +++++---
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/core/reactor.cc b/core/reactor.cc
index fe37c7cfec..fe0da03acc 100644
--- a/core/reactor.cc
+++ b/core/reactor.cc
@@ -347,8 +347,8 @@ reactor::signal_handler::signal_handler(int signo)
 }
 
 inter_thread_work_queue::inter_thread_work_queue()
-    : _pending(queue_length)
-    , _completed(queue_length)
+    : _pending()
+    , _completed()
     , _start_eventfd(0)
     , _complete_eventfd(0) {
 }
diff --git a/core/reactor.hh b/core/reactor.hh
index ac98a81c68..b42e951bf5 100644
--- a/core/reactor.hh
+++ b/core/reactor.hh
@@ -24,7 +24,7 @@
 #include <system_error>
 #include <chrono>
 #include <atomic>
-#include <boost/lockfree/queue.hpp>
+#include <boost/lockfree/spsc_queue.hpp>
 #include <boost/optional.hpp>
 #include <boost/program_options.hpp>
 #include "util/eclipse.hh"
@@ -305,8 +305,10 @@ class smp;
 class inter_thread_work_queue {
     static constexpr size_t queue_length = 128;
     struct work_item;
-    boost::lockfree::queue<work_item*> _pending;
-    boost::lockfree::queue<work_item*> _completed;
+    using lf_queue = boost::lockfree::spsc_queue<work_item*,
+                            boost::lockfree::capacity<queue_length>>;
+    lf_queue _pending;
+    lf_queue _completed;
     writeable_eventfd _start_eventfd;
     readable_eventfd _complete_eventfd;
     semaphore _queue_has_room = { queue_length };