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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/277572">277572</a></dd>
<dt>Author</dt> <dd>keith_miller@apple.com</dd>
<dt>Date</dt> <dd>2021-05-16 10:46:33 -0700 (Sun, 16 May 2021)</dd>
</dl>

<h3>Log Message</h3>
<pre>IsoAlignedMemoryAllocator should use BitVector
https://bugs.webkit.org/show_bug.cgi?id=225852

Reviewed by Mark Lam.

Right now IsoAlignedMemoryAllocator uses FastBitVector, which does
not have inline storage for small sizes. However, it's not
uncommon for IsoAlignedMemoryAllocator to be holding onto only a
few blocks. Those blocks may exist for a long time, which some
data indicates causes IsoAlignedMemoryAllocator's FastBitVector to
pin a full physical page for one 8 byte allocation. Since
accessing the commited blocks list is not a particularly hot
operation, we should just use a BitVector instead.

This seems to be perf neutral on benchmarks.

* heap/IsoAlignedMemoryAllocator.cpp:
(JSC::IsoAlignedMemoryAllocator::~IsoAlignedMemoryAllocator):
(JSC::IsoAlignedMemoryAllocator::tryAllocateAlignedMemory):
(JSC::IsoAlignedMemoryAllocator::freeAlignedMemory):
* heap/IsoAlignedMemoryAllocator.h:</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapIsoAlignedMemoryAllocatorcpp">trunk/Source/JavaScriptCore/heap/IsoAlignedMemoryAllocator.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapIsoAlignedMemoryAllocatorh">trunk/Source/JavaScriptCore/heap/IsoAlignedMemoryAllocator.h</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (277571 => 277572)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog    2021-05-16 17:18:30 UTC (rev 277571)
+++ trunk/Source/JavaScriptCore/ChangeLog       2021-05-16 17:46:33 UTC (rev 277572)
</span><span class="lines">@@ -1,3 +1,27 @@
</span><ins>+2021-05-16  Keith Miller  <keith_miller@apple.com>
+
+        IsoAlignedMemoryAllocator should use BitVector
+        https://bugs.webkit.org/show_bug.cgi?id=225852
+
+        Reviewed by Mark Lam.
+
+        Right now IsoAlignedMemoryAllocator uses FastBitVector, which does
+        not have inline storage for small sizes. However, it's not
+        uncommon for IsoAlignedMemoryAllocator to be holding onto only a
+        few blocks. Those blocks may exist for a long time, which some
+        data indicates causes IsoAlignedMemoryAllocator's FastBitVector to
+        pin a full physical page for one 8 byte allocation. Since
+        accessing the commited blocks list is not a particularly hot
+        operation, we should just use a BitVector instead.
+
+        This seems to be perf neutral on benchmarks.
+
+        * heap/IsoAlignedMemoryAllocator.cpp:
+        (JSC::IsoAlignedMemoryAllocator::~IsoAlignedMemoryAllocator):
+        (JSC::IsoAlignedMemoryAllocator::tryAllocateAlignedMemory):
+        (JSC::IsoAlignedMemoryAllocator::freeAlignedMemory):
+        * heap/IsoAlignedMemoryAllocator.h:
+
</ins><span class="cx"> 2021-05-16  Saam Barati  <sbarati@apple.com>
</span><span class="cx"> 
</span><span class="cx">         DFGVarargsForwardingPhase shouldn't consult Flush
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapIsoAlignedMemoryAllocatorcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/IsoAlignedMemoryAllocator.cpp (277571 => 277572)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/IsoAlignedMemoryAllocator.cpp   2021-05-16 17:18:30 UTC (rev 277571)
+++ trunk/Source/JavaScriptCore/heap/IsoAlignedMemoryAllocator.cpp      2021-05-16 17:46:33 UTC (rev 277572)
</span><span class="lines">@@ -1,5 +1,5 @@
</span><span class="cx"> /*
</span><del>- * Copyright (C) 2017 Apple Inc. All rights reserved.
</del><ins>+ * Copyright (C) 2017-2021 Apple Inc. All rights reserved.
</ins><span class="cx">  *
</span><span class="cx">  * Redistribution and use in source and binary forms, with or without
</span><span class="cx">  * modification, are permitted provided that the following conditions
</span><span class="lines">@@ -42,7 +42,7 @@
</span><span class="cx"> #if !ENABLE(MALLOC_HEAP_BREAKDOWN)
</span><span class="cx">     for (unsigned i = 0; i < m_blocks.size(); ++i) {
</span><span class="cx">         void* block = m_blocks[i];
</span><del>-        if (!m_committed[i])
</del><ins>+        if (!m_committed.quickGet(i))
</ins><span class="cx">             WTF::fastCommitAlignedMemory(block, MarkedBlock::blockSize);
</span><span class="cx">         fastAlignedFree(block);
</span><span class="cx">     }
</span><span class="lines">@@ -63,7 +63,7 @@
</span><span class="cx">     
</span><span class="cx">     m_firstUncommitted = m_committed.findBit(m_firstUncommitted, false);
</span><span class="cx">     if (m_firstUncommitted < m_blocks.size()) {
</span><del>-        m_committed[m_firstUncommitted] = true;
</del><ins>+        m_committed.quickSet(m_firstUncommitted);
</ins><span class="cx">         void* result = m_blocks[m_firstUncommitted];
</span><span class="cx">         WTF::fastCommitAlignedMemory(result, MarkedBlock::blockSize);
</span><span class="cx">         return result;
</span><span class="lines">@@ -77,7 +77,7 @@
</span><span class="cx">     m_blockIndices.add(result, index);
</span><span class="cx">     if (m_blocks.capacity() != m_committed.size())
</span><span class="cx">         m_committed.resize(m_blocks.capacity());
</span><del>-    m_committed[index] = true;
</del><ins>+    m_committed.quickSet(index);
</ins><span class="cx">     return result;
</span><span class="cx"> #endif
</span><span class="cx"> }
</span><span class="lines">@@ -92,7 +92,7 @@
</span><span class="cx">     auto iter = m_blockIndices.find(basePtr);
</span><span class="cx">     RELEASE_ASSERT(iter != m_blockIndices.end());
</span><span class="cx">     unsigned index = iter->value;
</span><del>-    m_committed[index] = false;
</del><ins>+    m_committed.quickClear(index);
</ins><span class="cx">     m_firstUncommitted = std::min(index, m_firstUncommitted);
</span><span class="cx">     WTF::fastDecommitAlignedMemory(basePtr, MarkedBlock::blockSize);
</span><span class="cx"> #endif
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapIsoAlignedMemoryAllocatorh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/IsoAlignedMemoryAllocator.h (277571 => 277572)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/IsoAlignedMemoryAllocator.h     2021-05-16 17:18:30 UTC (rev 277571)
+++ trunk/Source/JavaScriptCore/heap/IsoAlignedMemoryAllocator.h        2021-05-16 17:46:33 UTC (rev 277572)
</span><span class="lines">@@ -1,5 +1,5 @@
</span><span class="cx"> /*
</span><del>- * Copyright (C) 2017 Apple Inc. All rights reserved.
</del><ins>+ * Copyright (C) 2017-2021 Apple Inc. All rights reserved.
</ins><span class="cx">  *
</span><span class="cx">  * Redistribution and use in source and binary forms, with or without
</span><span class="cx">  * modification, are permitted provided that the following conditions
</span><span class="lines">@@ -26,8 +26,8 @@
</span><span class="cx"> #pragma once
</span><span class="cx"> 
</span><span class="cx"> #include "AlignedMemoryAllocator.h"
</span><ins>+#include <wtf/BitVector.h>
</ins><span class="cx"> #include <wtf/DebugHeap.h>
</span><del>-#include <wtf/FastBitVector.h>
</del><span class="cx"> #include <wtf/HashMap.h>
</span><span class="cx"> #include <wtf/Vector.h>
</span><span class="cx"> 
</span><span class="lines">@@ -55,7 +55,7 @@
</span><span class="cx"> #else
</span><span class="cx">     Vector<void*> m_blocks;
</span><span class="cx">     HashMap<void*, unsigned> m_blockIndices;
</span><del>-    FastBitVector m_committed;
</del><ins>+    BitVector m_committed;
</ins><span class="cx">     unsigned m_firstUncommitted { 0 };
</span><span class="cx">     Lock m_lock;
</span><span class="cx"> #endif
</span></span></pre>
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