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<title>[205022] trunk/Source/bmalloc</title>
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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/205022">205022</a></dd>
<dt>Author</dt> <dd>barraclough@apple.com</dd>
<dt>Date</dt> <dd>2016-08-26 10:02:37 -0700 (Fri, 26 Aug 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>bmalloc: speed up the lock slow path
https://bugs.webkit.org/show_bug.cgi?id=161058
Unreviewed rollout - this caused regressions <rdar://problem/28026089>.
* bmalloc.xcodeproj/project.pbxproj:
* bmalloc/ScopeExit.h: Removed.
* bmalloc/StaticMutex.cpp:
(bmalloc::StaticMutex::lockSlowCase):
* bmalloc/StaticMutex.h:
(bmalloc::StaticMutex::init):
* bmalloc/ThreadSwitch.h: Removed.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourcebmallocChangeLog">trunk/Source/bmalloc/ChangeLog</a></li>
<li><a href="#trunkSourcebmallocbmallocStaticMutexcpp">trunk/Source/bmalloc/bmalloc/StaticMutex.cpp</a></li>
<li><a href="#trunkSourcebmallocbmallocStaticMutexh">trunk/Source/bmalloc/bmalloc/StaticMutex.h</a></li>
<li><a href="#trunkSourcebmallocbmallocxcodeprojprojectpbxproj">trunk/Source/bmalloc/bmalloc.xcodeproj/project.pbxproj</a></li>
</ul>
<h3>Removed Paths</h3>
<ul>
<li><a href="#trunkSourcebmallocbmallocScopeExith">trunk/Source/bmalloc/bmalloc/ScopeExit.h</a></li>
<li><a href="#trunkSourcebmallocbmallocThreadSwitchh">trunk/Source/bmalloc/bmalloc/ThreadSwitch.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourcebmallocChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/ChangeLog (205021 => 205022)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/ChangeLog 2016-08-26 16:54:14 UTC (rev 205021)
+++ trunk/Source/bmalloc/ChangeLog 2016-08-26 17:02:37 UTC (rev 205022)
</span><span class="lines">@@ -1,3 +1,18 @@
</span><ins>+2016-08-26 Gavin Barraclough <barraclough@apple.com>
+
+ bmalloc: speed up the lock slow path
+ https://bugs.webkit.org/show_bug.cgi?id=161058
+
+ Unreviewed rollout - this caused regressions <rdar://problem/28026089>.
+
+ * bmalloc.xcodeproj/project.pbxproj:
+ * bmalloc/ScopeExit.h: Removed.
+ * bmalloc/StaticMutex.cpp:
+ (bmalloc::StaticMutex::lockSlowCase):
+ * bmalloc/StaticMutex.h:
+ (bmalloc::StaticMutex::init):
+ * bmalloc/ThreadSwitch.h: Removed.
+
</ins><span class="cx"> 2016-08-24 Andreas Kling <akling@apple.com>
</span><span class="cx">
</span><span class="cx"> Add bmalloc::api::isEnabled().
</span></span></pre></div>
<a id="trunkSourcebmallocbmallocScopeExith"></a>
<div class="delfile"><h4>Deleted: trunk/Source/bmalloc/bmalloc/ScopeExit.h (205021 => 205022)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc/ScopeExit.h 2016-08-26 16:54:14 UTC (rev 205021)
+++ trunk/Source/bmalloc/bmalloc/ScopeExit.h 2016-08-26 17:02:37 UTC (rev 205022)
</span><span class="lines">@@ -1,54 +0,0 @@
</span><del>-/*
- * Copyright (C) 2016 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
- * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include <type_traits>
-#include <utility>
-
-namespace bmalloc {
-
-template<typename ExitFunction>
-class ScopeExit {
-public:
- explicit ScopeExit(ExitFunction&& exitFunction)
- : m_exitFunction(exitFunction)
- {
- }
-
- ~ScopeExit()
- {
- m_exitFunction();
- }
-
-private:
- ExitFunction m_exitFunction;
-};
-
-template<typename ExitFunction>
-ScopeExit<ExitFunction> makeScopeExit(ExitFunction&& exitFunction)
-{
- return ScopeExit<ExitFunction>(std::forward<ExitFunction>(exitFunction));
-}
-
-} // namespace bmalloc
</del></span></pre></div>
<a id="trunkSourcebmallocbmallocStaticMutexcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/bmalloc/StaticMutex.cpp (205021 => 205022)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc/StaticMutex.cpp 2016-08-26 16:54:14 UTC (rev 205021)
+++ trunk/Source/bmalloc/bmalloc/StaticMutex.cpp 2016-08-26 17:02:37 UTC (rev 205022)
</span><span class="lines">@@ -23,31 +23,15 @@
</span><span class="cx"> * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
</span><span class="cx"> */
</span><span class="cx">
</span><del>-#include "ScopeExit.h"
</del><span class="cx"> #include "StaticMutex.h"
</span><del>-#include "ThreadSwitch.h"
</del><ins>+#include <thread>
</ins><span class="cx">
</span><span class="cx"> namespace bmalloc {
</span><span class="cx">
</span><span class="cx"> void StaticMutex::lockSlowCase()
</span><span class="cx"> {
</span><del>- // The longest critical section in bmalloc is much shorter than the
- // time it takes to make a system call to yield to the OS scheduler.
- // So, we try again a lot before we yield.
- static const size_t aLot = 256;
-
- if (!m_isSpinning.test_and_set()) {
- auto clear = makeScopeExit([&] { m_isSpinning.clear(); });
-
- for (size_t i = 0; i < aLot; ++i) {
- if (try_lock())
- return;
- }
- }
-
- // Avoid spinning pathologically.
</del><span class="cx"> while (!try_lock())
</span><del>- threadSwitch();
</del><ins>+ std::this_thread::yield();
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> } // namespace bmalloc
</span></span></pre></div>
<a id="trunkSourcebmallocbmallocStaticMutexh"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/bmalloc/StaticMutex.h (205021 => 205022)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc/StaticMutex.h 2016-08-26 16:54:14 UTC (rev 205021)
+++ trunk/Source/bmalloc/bmalloc/StaticMutex.h 2016-08-26 17:02:37 UTC (rev 205022)
</span><span class="lines">@@ -52,7 +52,6 @@
</span><span class="cx"> void lockSlowCase();
</span><span class="cx">
</span><span class="cx"> std::atomic_flag m_flag;
</span><del>- std::atomic_flag m_isSpinning;
</del><span class="cx"> };
</span><span class="cx">
</span><span class="cx"> static inline void sleep(
</span><span class="lines">@@ -79,7 +78,6 @@
</span><span class="cx"> inline void StaticMutex::init()
</span><span class="cx"> {
</span><span class="cx"> m_flag.clear();
</span><del>- m_isSpinning.clear();
</del><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> inline bool StaticMutex::try_lock()
</span></span></pre></div>
<a id="trunkSourcebmallocbmallocThreadSwitchh"></a>
<div class="delfile"><h4>Deleted: trunk/Source/bmalloc/bmalloc/ThreadSwitch.h (205021 => 205022)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc/ThreadSwitch.h 2016-08-26 16:54:14 UTC (rev 205021)
+++ trunk/Source/bmalloc/bmalloc/ThreadSwitch.h 2016-08-26 17:02:37 UTC (rev 205022)
</span><span class="lines">@@ -1,44 +0,0 @@
</span><del>-/*
- * Copyright (C) 2016 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
- * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#if BOS(DARWIN)
-#include <mach/thread_switch.h>
-#endif
-#include <thread>
-
-namespace bmalloc {
-
-inline void threadSwitch()
-{
- // yield() on Darwin will depress your priority to absolute 0 for 10ms,
- // and possibly clock down the CPU -- so we avoid it.
-#if BOS(DARWIN)
- swtch();
-#else
- std::this_thread::yield();
-#endif
-}
-
-} // namespace bmalloc
</del></span></pre></div>
<a id="trunkSourcebmallocbmallocxcodeprojprojectpbxproj"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/bmalloc.xcodeproj/project.pbxproj (205021 => 205022)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc.xcodeproj/project.pbxproj 2016-08-26 16:54:14 UTC (rev 205021)
+++ trunk/Source/bmalloc/bmalloc.xcodeproj/project.pbxproj 2016-08-26 17:02:37 UTC (rev 205022)
</span><span class="lines">@@ -24,8 +24,6 @@
</span><span class="cx"> 147DC6E31CA5B70B00724E8D /* Chunk.h in Headers */ = {isa = PBXBuildFile; fileRef = 147DC6E21CA5B70B00724E8D /* Chunk.h */; settings = {ATTRIBUTES = (Private, ); }; };
</span><span class="cx"> 14895D911A3A319C0006235D /* Environment.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 14895D8F1A3A319C0006235D /* Environment.cpp */; };
</span><span class="cx"> 14895D921A3A319C0006235D /* Environment.h in Headers */ = {isa = PBXBuildFile; fileRef = 14895D901A3A319C0006235D /* Environment.h */; settings = {ATTRIBUTES = (Private, ); }; };
</span><del>- 148EFAE81D6B953B008E721E /* ScopeExit.h in Headers */ = {isa = PBXBuildFile; fileRef = 148EFAE61D6B953B008E721E /* ScopeExit.h */; };
- 148EFAE91D6B953B008E721E /* ThreadSwitch.h in Headers */ = {isa = PBXBuildFile; fileRef = 148EFAE71D6B953B008E721E /* ThreadSwitch.h */; };
</del><span class="cx"> 14C8992B1CC485E70027A057 /* Map.h in Headers */ = {isa = PBXBuildFile; fileRef = 14C8992A1CC485E70027A057 /* Map.h */; settings = {ATTRIBUTES = (Private, ); }; };
</span><span class="cx"> 14C8992D1CC578330027A057 /* XLargeRange.h in Headers */ = {isa = PBXBuildFile; fileRef = 14C8992C1CC578330027A057 /* XLargeRange.h */; settings = {ATTRIBUTES = (Private, ); }; };
</span><span class="cx"> 14C919C918FCC59F0028DB43 /* BPlatform.h in Headers */ = {isa = PBXBuildFile; fileRef = 14C919C818FCC59F0028DB43 /* BPlatform.h */; settings = {ATTRIBUTES = (Private, ); }; };
</span><span class="lines">@@ -112,8 +110,6 @@
</span><span class="cx"> 1485656018A43DBA00ED6942 /* ObjectType.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ObjectType.h; path = bmalloc/ObjectType.h; sourceTree = "<group>"; };
</span><span class="cx"> 14895D8F1A3A319C0006235D /* Environment.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = Environment.cpp; path = bmalloc/Environment.cpp; sourceTree = "<group>"; };
</span><span class="cx"> 14895D901A3A319C0006235D /* Environment.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = Environment.h; path = bmalloc/Environment.h; sourceTree = "<group>"; };
</span><del>- 148EFAE61D6B953B008E721E /* ScopeExit.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ScopeExit.h; path = bmalloc/ScopeExit.h; sourceTree = "<group>"; };
- 148EFAE71D6B953B008E721E /* ThreadSwitch.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ThreadSwitch.h; path = bmalloc/ThreadSwitch.h; sourceTree = "<group>"; };
</del><span class="cx"> 14B650C518F39F4800751968 /* Base.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = Base.xcconfig; sourceTree = "<group>"; };
</span><span class="cx"> 14B650C618F39F4800751968 /* bmalloc.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = bmalloc.xcconfig; sourceTree = "<group>"; };
</span><span class="cx"> 14B650C718F39F4800751968 /* DebugRelease.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = DebugRelease.xcconfig; sourceTree = "<group>"; };
</span><span class="lines">@@ -266,11 +262,9 @@
</span><span class="cx"> 14446A0717A61FA400F9EA1D /* PerProcess.h */,
</span><span class="cx"> 144469FD17A61F1F00F9EA1D /* PerThread.h */,
</span><span class="cx"> 145F6878179E3A4400D65598 /* Range.h */,
</span><del>- 148EFAE61D6B953B008E721E /* ScopeExit.h */,
</del><span class="cx"> 143CB81A19022BC900B16A45 /* StaticMutex.cpp */,
</span><span class="cx"> 143CB81B19022BC900B16A45 /* StaticMutex.h */,
</span><span class="cx"> 1417F64F18B7280C0076FA3F /* Syscall.h */,
</span><del>- 148EFAE71D6B953B008E721E /* ThreadSwitch.h */,
</del><span class="cx"> 1479E21217A1A255006D4E9D /* Vector.h */,
</span><span class="cx"> 1479E21417A1A63E006D4E9D /* VMAllocate.h */,
</span><span class="cx"> );
</span><span class="lines">@@ -315,7 +309,6 @@
</span><span class="cx"> 4426E2831C839547008EB042 /* BSoftLinking.h in Headers */,
</span><span class="cx"> 14DD789018F48CEB00950702 /* Sizes.h in Headers */,
</span><span class="cx"> 14DD78C718F48D7500950702 /* BAssert.h in Headers */,
</span><del>- 148EFAE91D6B953B008E721E /* ThreadSwitch.h in Headers */,
</del><span class="cx"> 14DD78D018F48D7500950702 /* VMAllocate.h in Headers */,
</span><span class="cx"> 14DD78CE18F48D7500950702 /* Syscall.h in Headers */,
</span><span class="cx"> 14DD78C618F48D7500950702 /* AsyncTask.h in Headers */,
</span><span class="lines">@@ -323,7 +316,6 @@
</span><span class="cx"> 14895D921A3A319C0006235D /* Environment.h in Headers */,
</span><span class="cx"> 1400274A18F89C2300115C97 /* VMHeap.h in Headers */,
</span><span class="cx"> 1400274918F89C1300115C97 /* Heap.h in Headers */,
</span><del>- 148EFAE81D6B953B008E721E /* ScopeExit.h in Headers */,
</del><span class="cx"> 140FA00319CE429C00FFD3C8 /* BumpRange.h in Headers */,
</span><span class="cx"> 4426E2811C838EE0008EB042 /* Logging.h in Headers */,
</span><span class="cx"> 14DD78C518F48D7500950702 /* Algorithm.h in Headers */,
</span></span></pre>
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