[Experiment] purge-and-suspend

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

 // 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 "platform/Histogram.h"
+#include "public/platform/Platform.h"
+#include "third_party/zlib/google/compression_utils.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));
+        DCHECK(!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));
+        DCHECK(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();
@@ skipping 22 matching lines @@
 
 static const unsigned CompressibleStringImplSizeThrehold = 100000;
 
 void CompressibleStringImpl::compressAll()
 {
     compressibleStringTable().compressAll();
 }
 
 CompressibleStringImpl::CompressibleStringImpl(PassRefPtr<StringImpl> impl)
     : m_string(impl)
-    , m_isCompressed(false)
+    , m_originalLength(m_string.length())
+    , m_compressedData(nullptr)
+    , m_compressedDataSize(0)
 {
     if (originalContentSizeInBytes() > CompressibleStringImplSizeThrehold)
         compressibleStringTable().add(this);
 }
 
 CompressibleStringImpl::~CompressibleStringImpl()
 {
     if (originalContentSizeInBytes() > CompressibleStringImplSizeThrehold)
         compressibleStringTable().remove(this);
 }
 
 enum CompressibleStringCountType {
     StringWasCompressedInBackgroundTab,
     StringWasDecompressed,
     CompressibleStringCountTypeMax = StringWasDecompressed,
 };
 
 static void recordCompressibleStringCount(CompressibleStringCountType type)
 {
     DEFINE_THREAD_SAFE_STATIC_LOCAL(EnumerationHistogram, sringTypeHistogram, new EnumerationHistogram("Memory.CompressibleStringCount", CompressibleStringCountTypeMax + 1));
     sringTypeHistogram.count(type);
 }
 
-// compressString does nothing but collect UMA so far.
-// TODO(hajimehoshi): Implement this.
 void CompressibleStringImpl::compressString()
 {
     recordCompressibleStringCount(StringWasCompressedInBackgroundTab);
-    ASSERT(!isCompressed());
-    m_isCompressed = true;
+    DCHECK(!isCompressed());
+    DCHECK(!m_compressedData);
+    DCHECK(!m_compressedDataSize);
+
+    // TODO(hajimehoshi): Now components offers funcitons accepting only
+    // std::strings. This is not efficient. We should offer char* version.
+    std::string in, out;
+    if (m_string.is8Bit()) {
+        in = std::string(reinterpret_cast<const char*>(m_string.characters8()), originalContentSizeInBytes());

[esprehn, 2016/08/05 23:00:58]

ouch this is pretty bad it doubles the memory usage of the huge JS strings while
we're in the process of compressing them.

[tasak, 2016/08/08 04:47:36]

Acknowledged.

+        m_string = emptyString();
+    } else {
+        in = std::string(reinterpret_cast<const char*>(m_string.characters16()),  originalContentSizeInBytes());
+        m_string = emptyString16Bit();
+    }
+    compression::GzipCompress(in, &out);
+
+    m_compressedData = WTF::Partitions::fastMalloc(out.size(), "CompressibleString");
+    memcpy(m_compressedData, out.c_str(), out.size());
+    m_compressedDataSize = out.size();
 }
 
-// decompressString does nothing but collect UMA so far.
-// TODO(hajimehoshi): Implement this.
 void CompressibleStringImpl::decompressString()
 {
     // TODO(hajimehoshi): We wanted to tell whether decompressing in a
     // background tab or a foreground tab, but this was impossible. For example,
     // one renderer process of a new tab page is used for multiple tabs.
     // Another example is that reloading a page will re-use the process with a
     // new Page object and updating a static variable along with reloading will
     // be complex. See also crbug/581266. We will revisit when the situation
     // changes.
     recordCompressibleStringCount(StringWasDecompressed);
-    ASSERT(isCompressed());
-    m_isCompressed = false;
+    DCHECK(isCompressed());
+    DCHECK(m_compressedData);
+    DCHECK(m_compressedDataSize);
+
+    std::string in(static_cast<const char*>(m_compressedData), m_compressedDataSize);
+    std::string out;
+    compression::GzipUncompress(in, &out);

[esprehn, 2016/08/05 23:00:58]

ditto

[tasak, 2016/08/08 04:47:36]

Acknowledged.

+
+    if (is8Bit()) {
+        LChar* data = nullptr;
+        m_string = StringImpl::createUninitialized(out.size() / sizeof(LChar), data);
+        memcpy(data, out.c_str(), out.size());
+    } else {
+        UChar* data = nullptr;
+        m_string = StringImpl::createUninitialized(out.size() / sizeof(UChar), data);
+        memcpy(data, out.c_str(), out.size());
+    }
+
+    WTF::Partitions::fastFree(m_compressedData);
+    m_compressedData = nullptr;
+    m_compressedDataSize = 0;
+    DCHECK(m_originalLength == m_string.length());
 }
 
 } // namespace blink