Experimental CompressibleString UMA

third_party/WebKit/Source/platform/text/CompressibleString.cpp

Index: third_party/WebKit/Source/platform/text/CompressibleString.cpp
diff --git a/third_party/WebKit/Source/platform/text/CompressibleString.cpp b/third_party/WebKit/Source/platform/text/CompressibleString.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..63f597f61e968437a416dfe68032dae1db5b3f86
--- /dev/null
+++ b/third_party/WebKit/Source/platform/text/CompressibleString.cpp
@@ -0,0 +1,201 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "platform/text/CompressibleString.h"
+
+#include "public/platform/Platform.h"
+#include "wtf/Assertions.h"
+#include "wtf/WTFThreadData.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+class CompressibleStringTable {
+    WTF_MAKE_NONCOPYABLE(CompressibleStringTable);
+public:
+    static CompressibleStringTable* create(WTFThreadData& data)
+    {
+        data.m_compressibleStringTable = new CompressibleStringTable;
+        data.m_compressibleStringTableDestructor = CompressibleStringTable::destroy;
+        return data.m_compressibleStringTable;
+    }
+
+    void add(CompressibleStringImpl* string)
+    {
+        ASSERT(!m_table.contains(string));
+        m_table.add(string);
+    }
+
+    bool contains(CompressibleStringImpl* string) const
+    {
+        return m_table.contains(string);
+    }
+
+    void remove(CompressibleStringImpl* string)
+    {
+        ASSERT(m_table.contains(string));
+        m_table.remove(string);
+    }
+
+    void compressAll()
+    {
+        HashSet<CompressibleStringImpl*>::iterator end = m_table.end();
+        for (HashSet<CompressibleStringImpl*>::iterator iter = m_table.begin(); iter != end; ++iter) {
+            CompressibleStringImpl* string = *iter;
+            if (!string->isCompressed())
+                string->compressString();
+        }
+    }
+
+private:
+    CompressibleStringTable() { }
+
+    static void destroy(CompressibleStringTable* table)
+    {
+        delete table;
+    }
+
+    HashSet<CompressibleStringImpl*> m_table;
+};
+
+static const int CompressibleStringImplSizeThrehold = 100000;
+
+void initializeCompressibleStringTable()
+{
+    WTFThreadData& data = wtfThreadData();
+    ASSERT(!data.compressibleStringTable());
+    CompressibleStringTable::create(data);
+}
+
+static inline CompressibleStringTable& compressibleStringTable()
+{
+    WTFThreadData& data = wtfThreadData();
+    ASSERT(data.compressibleStringTable());
+    return *data.compressibleStringTable();
+}
+
+bool CompressibleStringImpl::s_isPageBackground = false;
+
+void CompressibleStringImpl::compressAll()
+{
+    compressibleStringTable().compressAll();
+}
+
+void CompressibleStringImpl::setPageBackground(bool isPageBackground)
+{
+    s_isPageBackground = isPageBackground;
+}
+
+CompressibleStringImpl::CompressibleStringImpl()

[haraken, 2016/01/19 07:43:35]

For performance reasons, I'd suggest inlining most of the CompressibleImpl's
methods.

[hajimehoshi, 2016/01/19 10:19:20]

Done.

+    : m_string()
+    , m_isCompressed(false)
+{
+}
+
+CompressibleStringImpl::CompressibleStringImpl(PassRefPtr<StringImpl> impl)

[haraken, 2016/01/19 07:43:35]

Inline.

[hajimehoshi, 2016/01/19 10:19:21]

Hmm, I don't want to expose compressibleStringTable() in the header file and
keep this as it is.

+    : m_string(impl)
+    , m_isCompressed(false)
+{
+    ASSERT(impl);
+    if (originalContentSizeInBytes() > CompressibleStringImplSizeThrehold)
+        compressibleStringTable().add(this);
+}
+
+CompressibleStringImpl::~CompressibleStringImpl()
+{
+    if (compressibleStringTable().contains(this))

[haraken, 2016/01/19 07:43:35]

A better condition would be:

  if (originalContentSizeInBytes() > CompressibleStringImplSizeThrehold)

If compressibleStringTable().contains(this) doesn't hold, you'll hit an assert
in the following remove.

[hajimehoshi, 2016/01/19 10:19:20]

Done.

+        compressibleStringTable().remove(this);
+}
+
+unsigned CompressibleStringImpl::originalContentSizeInBytes() const

[haraken, 2016/01/19 07:43:35]

Inline.

[hajimehoshi, 2016/01/19 10:19:21]

Done.

+{
+    if (is8Bit())
+        return originalLength() * sizeof(LChar);
+    return originalLength() * sizeof(UChar);
+}
+
+// TODO(hajimehoshi): Update this once we implement compression.
+unsigned CompressibleStringImpl::currentSizeInBytes() const

[haraken, 2016/01/19 07:43:35]

Inline.

[hajimehoshi, 2016/01/19 10:19:21]

Done.

+{
+    return originalContentSizeInBytes();
+}
+
+const String& CompressibleStringImpl::toString()

[haraken, 2016/01/19 07:43:35]

It would be better to inline this.

[hajimehoshi, 2016/01/19 10:19:21]

Done.

+{
+    if (UNLIKELY(isCompressed()))
+        decompressString();
+    return m_string;
+}
+
+const LChar* CompressibleStringImpl::characters8()

[haraken, 2016/01/19 07:43:35]

Inline.

[hajimehoshi, 2016/01/19 10:19:21]

Done.

+{
+    return toString().characters8();
+}
+
+const UChar* CompressibleStringImpl::characters16()

[haraken, 2016/01/19 07:43:35]

Inline.

[hajimehoshi, 2016/01/19 10:19:21]

Done.

+{
+    return toString().characters16();
+}
+
+enum {
+    CompressingInBackgroundTab,

[haraken, 2016/01/19 07:43:35]

StringWasCompressedInBackgroundTab
StringWasDecompressedInBackgroundTab
StringWasDecompressedInForegroundTab

?

[hajimehoshi, 2016/01/19 10:19:21]

Done.

+    DecompressingInBackgroundTab,
+    DecompressingInForegroundTab,
+};
+
+static const char* histogramName()
+{
+    return "Memory.CompressibleStringCount";
+}
+
+// compressString does nothing but collect UMA so far.
+// TODO(hajimehoshi): Implement this.
+void CompressibleStringImpl::compressString()
+{
+    if (s_isPageBackground)

[haraken, 2016/01/19 07:43:35]

Shouldn't this be:

  ASSERT(s_isPageBackground);

?

[hajimehoshi, 2016/01/19 10:19:21]

Done.

+        Platform::current()->histogramCustomCounts(histogramName(), CompressingInBackgroundTab, 0, 10000, 50);
+
+    ASSERT(!isCompressed());
+    m_isCompressed = true;
+}
+
+// decompressString does nothing but collect UMA so far.
+// TODO(hajimehoshi): Implement this.
+void CompressibleStringImpl::decompressString()
+{
+    if (s_isPageBackground)
+        Platform::current()->histogramCustomCounts(histogramName(), DecompressingInBackgroundTab, 0, 10000, 50);
+    else
+        Platform::current()->histogramCustomCounts(histogramName(), DecompressingInForegroundTab, 0, 10000, 50);
+
+    ASSERT(isCompressed());
+    m_isCompressed = false;
+}
+
+CompressibleString::CompressibleString()

[haraken, 2016/01/19 07:43:35]

Inline these methods.

[hajimehoshi, 2016/01/19 10:19:21]

Done.

+    : m_impl(nullptr)
+{
+}
+
+CompressibleString::CompressibleString(const CompressibleString& rhs)
+    : m_impl(rhs.m_impl)
+{
+}
+
+CompressibleString::CompressibleString(PassRefPtr<StringImpl> impl)
+    : m_impl(impl ? adoptRef(new CompressibleStringImpl(impl)) : nullptr)
+{
+}
+
+void CompressibleString::compressString() const
+{
+    m_impl->compressString();
+}
+
+void CompressibleString::decompressString() const
+{
+    m_impl->decompressString();
+}
+
+} // namespace blink