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<title>[214336] trunk/Source/JavaScriptCore</title>
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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/214336">214336</a></dd>
<dt>Author</dt> <dd>utatane.tea@gmail.com</dd>
<dt>Date</dt> <dd>2017-03-23 22:31:51 -0700 (Thu, 23 Mar 2017)</dd>
</dl>
<h3>Log Message</h3>
<pre>[JSC] Use WeakRandom for SamplingProfiler interval fluctuation
https://bugs.webkit.org/show_bug.cgi?id=170045
Reviewed by Mark Lam.
It is unnecessary to use cryptographicallyRandomNumber for SamplingProfiler
interval fluctuation. Use WeakRandom instead.
* runtime/SamplingProfiler.cpp:
(JSC::SamplingProfiler::SamplingProfiler):
(JSC::SamplingProfiler::timerLoop):
* runtime/SamplingProfiler.h:</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeSamplingProfilercpp">trunk/Source/JavaScriptCore/runtime/SamplingProfiler.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeSamplingProfilerh">trunk/Source/JavaScriptCore/runtime/SamplingProfiler.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (214335 => 214336)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2017-03-24 05:14:13 UTC (rev 214335)
+++ trunk/Source/JavaScriptCore/ChangeLog 2017-03-24 05:31:51 UTC (rev 214336)
</span><span class="lines">@@ -1,3 +1,18 @@
</span><ins>+2017-03-23 Yusuke Suzuki <utatane.tea@gmail.com>
+
+ [JSC] Use WeakRandom for SamplingProfiler interval fluctuation
+ https://bugs.webkit.org/show_bug.cgi?id=170045
+
+ Reviewed by Mark Lam.
+
+ It is unnecessary to use cryptographicallyRandomNumber for SamplingProfiler
+ interval fluctuation. Use WeakRandom instead.
+
+ * runtime/SamplingProfiler.cpp:
+ (JSC::SamplingProfiler::SamplingProfiler):
+ (JSC::SamplingProfiler::timerLoop):
+ * runtime/SamplingProfiler.h:
+
</ins><span class="cx"> 2017-03-23 Mark Lam <mark.lam@apple.com>
</span><span class="cx">
</span><span class="cx"> Array.prototype.splice behaves incorrectly when the VM is "having a bad time".
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeSamplingProfilercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/SamplingProfiler.cpp (214335 => 214336)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/SamplingProfiler.cpp 2017-03-24 05:14:13 UTC (rev 214335)
+++ trunk/Source/JavaScriptCore/runtime/SamplingProfiler.cpp 2017-03-24 05:31:51 UTC (rev 214336)
</span><span class="lines">@@ -47,7 +47,6 @@
</span><span class="cx"> #include "StrongInlines.h"
</span><span class="cx"> #include "VM.h"
</span><span class="cx"> #include <wtf/HashSet.h>
</span><del>-#include <wtf/RandomNumber.h>
</del><span class="cx"> #include <wtf/RefPtr.h>
</span><span class="cx"> #include <wtf/text/StringBuilder.h>
</span><span class="cx">
</span><span class="lines">@@ -277,6 +276,7 @@
</span><span class="cx">
</span><span class="cx"> SamplingProfiler::SamplingProfiler(VM& vm, RefPtr<Stopwatch>&& stopwatch)
</span><span class="cx"> : m_vm(vm)
</span><ins>+ , m_weakRandom()
</ins><span class="cx"> , m_stopwatch(WTFMove(stopwatch))
</span><span class="cx"> , m_timingInterval(std::chrono::microseconds(Options::sampleInterval()))
</span><span class="cx"> , m_threadIdentifier(0)
</span><span class="lines">@@ -328,7 +328,7 @@
</span><span class="cx"> // fluctuation here. The main idea is to prevent our timer from being in sync
</span><span class="cx"> // with some system process such as a scheduled context switch.
</span><span class="cx"> // http://plv.colorado.edu/papers/mytkowicz-pldi10.pdf
</span><del>- double randomSignedNumber = (randomNumber() * 2.0) - 1.0; // A random number between [-1, 1).
</del><ins>+ double randomSignedNumber = (m_weakRandom.get() * 2.0) - 1.0; // A random number between [-1, 1).
</ins><span class="cx"> std::chrono::microseconds randomFluctuation = std::chrono::microseconds(static_cast<uint64_t>(randomSignedNumber * static_cast<double>(m_timingInterval.count()) * 0.20l));
</span><span class="cx"> std::this_thread::sleep_for(m_timingInterval - std::min(m_timingInterval, stackTraceProcessingTime) + randomFluctuation);
</span><span class="cx"> }
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeSamplingProfilerh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/SamplingProfiler.h (214335 => 214336)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/SamplingProfiler.h 2017-03-24 05:14:13 UTC (rev 214335)
+++ trunk/Source/JavaScriptCore/runtime/SamplingProfiler.h 2017-03-24 05:31:51 UTC (rev 214336)
</span><span class="lines">@@ -35,6 +35,7 @@
</span><span class="cx"> #include <wtf/Lock.h>
</span><span class="cx"> #include <wtf/Stopwatch.h>
</span><span class="cx"> #include <wtf/Vector.h>
</span><ins>+#include <wtf/WeakRandom.h>
</ins><span class="cx">
</span><span class="cx"> namespace JSC {
</span><span class="cx">
</span><span class="lines">@@ -190,6 +191,7 @@
</span><span class="cx"> void takeSample(const AbstractLocker&, std::chrono::microseconds& stackTraceProcessingTime);
</span><span class="cx">
</span><span class="cx"> VM& m_vm;
</span><ins>+ WeakRandom m_weakRandom;
</ins><span class="cx"> RefPtr<Stopwatch> m_stopwatch;
</span><span class="cx"> Vector<StackTrace> m_stackTraces;
</span><span class="cx"> Vector<UnprocessedStackTrace> m_unprocessedStackTraces;
</span></span></pre>
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