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List:       webkit-changes
Subject:    [webkit-changes] [252621] trunk/Source/bmalloc
From:       basuke.suzuki () sony ! com
Date:       2019-11-19 3:29:12
Message-ID: 20191119032912.5205F10051CB () svn ! webkit ! org
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<div id="msg">
<dl class="meta">
<dt>Revision</dt> <dd><a \
href="http://trac.webkit.org/projects/webkit/changeset/252621">252621</a></dd> \
<dt>Author</dt> <dd>basuke.suzuki@sony.com</dd> <dt>Date</dt> <dd>2019-11-18 19:29:12 \
-0800 (Mon, 18 Nov 2019)</dd> </dl>

<h3>Log Message</h3>
<pre>[bmalloc] Some chunks have unused region in the tail of its memory block.
https://bugs.webkit.org/show_bug.cgi?id=204286

Reviewed by Yusuke Suzuki.

When chunk is initialized, some amount of memory are not used and be kept untouched \
until its end. This patch tries to decommit those region at the end of \
initialization.

For instance, think about the case that the pageClass is 5. Then pageSize is 24k. \
With this pageSize, a chunk can hold 42 pages and its size is 24k * 42 = 1008k which \
is smaller than chunkSize = 1024k. Here is the complete result:

        page    page    page
        class   size    count   remainings
        ----------------------------------
        0       4kB     256     0
        1       8kB     128     0
        2       12kB    85      4kB
        3       16kB    64      0
        4       20kB    51      4kB
        5       24kB    42      16kB
        6       28kB    36      16kB
        7       32kB    32      0
        8       36kB    28      16kB
        9       40kB    25      24kB
        10      44kB    23      12kB
        11      48kB    21      16kB
        12      52kB    19      36kB
        13      56kB    18      16kB
        14      60kB    17      4kB
        15      64kB    16      0

Tested on Mac testmem and result is almost same or in error margin.

        Before:                                 After:
        end score:           8.5425 MB          end score:           8.5127 MB
        peak score:          8.7997 MB          peak score:          8.7884 MB
        total memory score:  8.6702 MB          total memory score:  8.6495 MB
        time score:          668.19 ms          time score:          666.27 ms

* bmalloc/Chunk.h:
(bmalloc::Chunk::metadataSize):
(bmalloc::forEachPage):
* bmalloc/Heap.cpp:
(bmalloc::Heap::allocateSmallChunk):</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourcebmallocChangeLog">trunk/Source/bmalloc/ChangeLog</a></li>
<li><a href="#trunkSourcebmallocbmallocChunkh">trunk/Source/bmalloc/bmalloc/Chunk.h</a></li>
 <li><a href="#trunkSourcebmallocbmallocHeapcpp">trunk/Source/bmalloc/bmalloc/Heap.cpp</a></li>
 </ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourcebmallocChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/ChangeLog (252620 => \
252621)</h4> <pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/ChangeLog	2019-11-19 03:16:44 UTC (rev \
                252620)
+++ trunk/Source/bmalloc/ChangeLog	2019-11-19 03:29:12 UTC (rev 252621)
</span><span class="lines">@@ -1,3 +1,51 @@
</span><ins>+2019-11-18  Basuke Suzuki  &lt;basuke.suzuki@sony.com&gt;
+
+        [bmalloc] Some chunks have unused region in the tail of its memory block.
+        https://bugs.webkit.org/show_bug.cgi?id=204286
+
+        Reviewed by Yusuke Suzuki.
+
+        When chunk is initialized, some amount of memory are not used and be kept \
untouched until its end. +        This patch tries to decommit those region at the \
end of initialization. +
+        For instance, think about the case that the pageClass is 5. Then pageSize is \
24k. With this pageSize, +        a chunk can hold 42 pages and its size is 24k * 42 \
= 1008k which is smaller than chunkSize = 1024k. +        Here is the complete \
result: +
+                page    page    page
+                class   size    count   remainings
+                ----------------------------------
+                0       4kB     256     0
+                1       8kB     128     0
+                2       12kB    85      4kB
+                3       16kB    64      0
+                4       20kB    51      4kB
+                5       24kB    42      16kB
+                6       28kB    36      16kB
+                7       32kB    32      0
+                8       36kB    28      16kB
+                9       40kB    25      24kB
+                10      44kB    23      12kB
+                11      48kB    21      16kB
+                12      52kB    19      36kB
+                13      56kB    18      16kB
+                14      60kB    17      4kB
+                15      64kB    16      0
+
+        Tested on Mac testmem and result is almost same or in error margin.
+
+                Before:                                 After:
+                end score:           8.5425 MB          end score:           8.5127 \
MB +                peak score:          8.7997 MB          peak score:          \
8.7884 MB +                total memory score:  8.6702 MB          total memory \
score:  8.6495 MB +                time score:          668.19 ms          time \
score:          666.27 ms +
+        * bmalloc/Chunk.h:
+        (bmalloc::Chunk::metadataSize):
+        (bmalloc::forEachPage):
+        * bmalloc/Heap.cpp:
+        (bmalloc::Heap::allocateSmallChunk):
+
</ins><span class="cx"> 2019-11-15  Basuke Suzuki  &lt;basuke.suzuki@sony.com&gt;
</span><span class="cx"> 
</span><span class="cx">         [bmalloc] The tracking of freeableMemory of Heap \
doesn't count Chunk's metadata size. </span></span></pre></div>
<a id="trunkSourcebmallocbmallocChunkh"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/bmalloc/Chunk.h (252620 => \
252621)</h4> <pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc/Chunk.h	2019-11-19 03:16:44 UTC \
                (rev 252620)
+++ trunk/Source/bmalloc/bmalloc/Chunk.h	2019-11-19 03:29:12 UTC (rev 252621)
</span><span class="lines">@@ -38,6 +38,7 @@
</span><span class="cx"> class Chunk : public ListNode&lt;Chunk&gt; {
</span><span class="cx"> public:
</span><span class="cx">     static Chunk* get(void*);
</span><ins>+    static size_t metadataSize(size_t pageSize);
</ins><span class="cx"> 
</span><span class="cx">     Chunk(size_t pageSize);
</span><span class="cx">     
</span><span class="lines">@@ -73,13 +74,16 @@
</span><span class="cx">     }
</span><span class="cx"> };
</span><span class="cx"> 
</span><del>-template&lt;typename Function&gt; void forEachPage(Chunk* chunk, size_t \
pageSize, Function function) </del><ins>+inline size_t Chunk::metadataSize(size_t \
pageSize) </ins><span class="cx"> {
</span><span class="cx">     // We align to at least the page size so we can service \
aligned allocations </span><span class="cx">     // at equal and smaller powers of \
two, and also so we can vmDeallocatePhysicalPages(). </span><del>-    size_t \
metadataSize = roundUpToMultipleOfNonPowerOfTwo(pageSize, sizeof(Chunk)); \
</del><ins>+    return roundUpToMultipleOfNonPowerOfTwo(pageSize, sizeof(Chunk)); +}
</ins><span class="cx"> 
</span><del>-    Object begin(chunk, metadataSize);
</del><ins>+template&lt;typename Function&gt; void forEachPage(Chunk* chunk, size_t \
pageSize, Function function) +{
+    Object begin(chunk, Chunk::metadataSize(pageSize));
</ins><span class="cx">     Object end(chunk, chunkSize);
</span><span class="cx"> 
</span><span class="cx">     for (auto it = begin; it + pageSize &lt;= end; it = it + \
pageSize) </span></span></pre></div>
<a id="trunkSourcebmallocbmallocHeapcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/bmalloc/Heap.cpp (252620 => \
252621)</h4> <pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc/Heap.cpp	2019-11-19 03:16:44 UTC \
                (rev 252620)
+++ trunk/Source/bmalloc/bmalloc/Heap.cpp	2019-11-19 03:29:12 UTC (rev 252621)
</span><span class="lines">@@ -286,7 +286,11 @@
</span><span class="cx">         });
</span><span class="cx"> 
</span><span class="cx">         m_freeableMemory += accountedInFreeable;
</span><del>-        
</del><ins>+
+        auto decommitSize = chunkSize - Chunk::metadataSize(pageSize) - \
accountedInFreeable; +        if (decommitSize &gt; 0)
+            vmDeallocatePhysicalPagesSloppy(Chunk::get(chunk)-&gt;address(chunkSize \
- decommitSize), decommitSize); +
</ins><span class="cx">         m_scavenger-&gt;schedule(0);
</span><span class="cx"> 
</span><span class="cx">         return chunk;
</span></span></pre>
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