From: Lucian Grijincu <lucian@fb.com>
Date: Tue, 15 Apr 2014 03:15:10 +0000 (-0700)
Subject: folly: improve ProducerConsumerQueueBenchmark (misplaced doNotOptimizeAway)
X-Git-Tag: v0.22.0~606
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e39dfd9da543edf915060d4f981ae145d8b90c2b;p=folly.git

folly: improve ProducerConsumerQueueBenchmark (misplaced doNotOptimizeAway)

Summary:
as per discussion from https://phabricator.fb.com/D1274352

After changing the queue length to be a small value (100) I didn't see
improvement from cache alignment of atomics (too much noise). Dropping
that and just fixing the benchmark.

Test Plan: n/a

Reviewed By: ngbronson@fb.com

FB internal diff: D1276591
---

diff --git a/folly/test/ProducerConsumerQueueBenchmark.cpp b/folly/test/ProducerConsumerQueueBenchmark.cpp
index 52a92518..cea07874 100644
--- a/folly/test/ProducerConsumerQueueBenchmark.cpp
+++ b/folly/test/ProducerConsumerQueueBenchmark.cpp
@@ -72,8 +72,8 @@ struct ThroughputTest {
     for (int i = 0; i < iters_; ++i) {
       ThroughputType item = 0;
       while (!queue_.read(item)) {
-        doNotOptimizeAway(item);
       }
+      doNotOptimizeAway(item);
     }
   }