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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/115379">115379</a></dd>
<dt>Author</dt> <dd>antti@apple.com</dd>
<dt>Date</dt> <dd>2012-04-26 15:26:35 -0700 (Thu, 26 Apr 2012)</dd>
</dl>
<h3>Log Message</h3>
<pre>Cache parsed stylesheets
https://bugs.webkit.org/show_bug.cgi?id=85004
Reviewed by Andreas Kling.
CSS parsing is 1-2% of WebKit CPU usage on average pages, more on sites with large stylesheets.
We currently reparse all stylesheets from source text when they are encountered again. In many
browsing scenarios we can eliminate lot of this by caching the parsed stylesheets. For example
it is very common for subpages of a site to share the stylesheets.
This patch enables memory caching for stylesheet loaded using the <link> element. Only stylesheets
that have no import rules are cacheable for now.
Cached stylesheets are copied on restore so there is no sharing (and no memory wins) yet.
In the future we will also be able to share the actual data structures between pages for
significant memory savings.
After browsing around for a while <5% of the memory cache data was in parsed stylesheets so this
does not bloat the cache significantly.
* css/CSSStyleSheet.cpp:
(WebCore):
(WebCore::StyleSheetInternal::estimatedSizeInBytes):
Estimate stylesheet size so we can handle decoded data pruning correctly.
* css/CSSStyleSheet.h:
(StyleSheetInternal):
* css/StylePropertySet.cpp:
(WebCore::StylePropertySet::averageSizeInBytes):
(WebCore):
* css/StylePropertySet.h:
(StylePropertySet):
* css/StyleRule.cpp:
(WebCore::StyleRule::averageSizeInBytes):
(WebCore):
* css/StyleRule.h:
(StyleRule):
* html/HTMLLinkElement.cpp:
(WebCore::HTMLLinkElement::setCSSStyleSheet):
Save and restore parsed stylesheet. The current CSS parse context must be identical to the cached
stylesheets. This ensures that the parsing results would be identical.
* loader/cache/CachedCSSStyleSheet.cpp:
(WebCore):
(WebCore::CachedCSSStyleSheet::destroyDecodedData):
(WebCore::CachedCSSStyleSheet::restoreParsedStyleSheet):
(WebCore::CachedCSSStyleSheet::saveParsedStyleSheet):
* loader/cache/CachedCSSStyleSheet.h:
The parsed stylesheet cache is considered decoded data, similar to the image bitmaps. It uses the
same mechanism for pruning.
(WebCore):
(CachedCSSStyleSheet):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorecssCSSStyleSheetcpp">trunk/Source/WebCore/css/CSSStyleSheet.cpp</a></li>
<li><a href="#trunkSourceWebCorecssCSSStyleSheeth">trunk/Source/WebCore/css/CSSStyleSheet.h</a></li>
<li><a href="#trunkSourceWebCorecssStylePropertySetcpp">trunk/Source/WebCore/css/StylePropertySet.cpp</a></li>
<li><a href="#trunkSourceWebCorecssStylePropertySeth">trunk/Source/WebCore/css/StylePropertySet.h</a></li>
<li><a href="#trunkSourceWebCorecssStyleRulecpp">trunk/Source/WebCore/css/StyleRule.cpp</a></li>
<li><a href="#trunkSourceWebCorecssStyleRuleh">trunk/Source/WebCore/css/StyleRule.h</a></li>
<li><a href="#trunkSourceWebCorehtmlHTMLLinkElementcpp">trunk/Source/WebCore/html/HTMLLinkElement.cpp</a></li>
<li><a href="#trunkSourceWebCoreloadercacheCachedCSSStyleSheetcpp">trunk/Source/WebCore/loader/cache/CachedCSSStyleSheet.cpp</a></li>
<li><a href="#trunkSourceWebCoreloadercacheCachedCSSStyleSheeth">trunk/Source/WebCore/loader/cache/CachedCSSStyleSheet.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/ChangeLog 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -1,3 +1,62 @@
</span><ins>+2012-04-26 Antti Koivisto <antti@apple.com>
+
+ Cache parsed stylesheets
+ https://bugs.webkit.org/show_bug.cgi?id=85004
+
+ Reviewed by Andreas Kling.
+
+ CSS parsing is 1-2% of WebKit CPU usage on average pages, more on sites with large stylesheets.
+ We currently reparse all stylesheets from source text when they are encountered again. In many
+ browsing scenarios we can eliminate lot of this by caching the parsed stylesheets. For example
+ it is very common for subpages of a site to share the stylesheets.
+
+ This patch enables memory caching for stylesheet loaded using the <link> element. Only stylesheets
+ that have no import rules are cacheable for now.
+
+ Cached stylesheets are copied on restore so there is no sharing (and no memory wins) yet.
+ In the future we will also be able to share the actual data structures between pages for
+ significant memory savings.
+
+ After browsing around for a while <5% of the memory cache data was in parsed stylesheets so this
+ does not bloat the cache significantly.
+
+ * css/CSSStyleSheet.cpp:
+ (WebCore):
+ (WebCore::StyleSheetInternal::estimatedSizeInBytes):
+
+ Estimate stylesheet size so we can handle decoded data pruning correctly.
+
+ * css/CSSStyleSheet.h:
+ (StyleSheetInternal):
+ * css/StylePropertySet.cpp:
+ (WebCore::StylePropertySet::averageSizeInBytes):
+ (WebCore):
+ * css/StylePropertySet.h:
+ (StylePropertySet):
+ * css/StyleRule.cpp:
+ (WebCore::StyleRule::averageSizeInBytes):
+ (WebCore):
+ * css/StyleRule.h:
+ (StyleRule):
+ * html/HTMLLinkElement.cpp:
+ (WebCore::HTMLLinkElement::setCSSStyleSheet):
+
+ Save and restore parsed stylesheet. The current CSS parse context must be identical to the cached
+ stylesheets. This ensures that the parsing results would be identical.
+
+ * loader/cache/CachedCSSStyleSheet.cpp:
+ (WebCore):
+ (WebCore::CachedCSSStyleSheet::destroyDecodedData):
+ (WebCore::CachedCSSStyleSheet::restoreParsedStyleSheet):
+ (WebCore::CachedCSSStyleSheet::saveParsedStyleSheet):
+ * loader/cache/CachedCSSStyleSheet.h:
+
+ The parsed stylesheet cache is considered decoded data, similar to the image bitmaps. It uses the
+ same mechanism for pruning.
+
+ (WebCore):
+ (CachedCSSStyleSheet):
+
</ins><span class="cx"> 2012-04-26 Anders Carlsson <andersca@apple.com>
</span><span class="cx">
</span><span class="cx"> A TileCache should never outlive its WebTileCacheLayer
</span></span></pre></div>
<a id="trunkSourceWebCorecssCSSStyleSheetcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/css/CSSStyleSheet.cpp (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/css/CSSStyleSheet.cpp 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/css/CSSStyleSheet.cpp 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -72,6 +72,24 @@
</span><span class="cx"> }
</span><span class="cx"> #endif
</span><span class="cx">
</span><ins>+// Rough size estimate for the memory cache.
+unsigned StyleSheetInternal::estimatedSizeInBytes() const
+{
+ // Note that this does not take into account size of the strings hanging from various objects.
+ // The assumption is that nearly all of of them are atomic and would exist anyway.
+ unsigned size = sizeof(*this);
+
+ // FIXME: This ignores the children of media and region rules.
+ // Most rules are StyleRules.
+ size += ruleCount() * StyleRule::averageSizeInBytes();
+
+ for (unsigned i = 0; i < m_importRules.size(); ++i) {
+ if (StyleSheetInternal* sheet = m_importRules[i]->styleSheet())
+ size += sheet->estimatedSizeInBytes();
+ }
+ return size;
+}
+
</ins><span class="cx"> StyleSheetInternal::StyleSheetInternal(StyleRuleImport* ownerRule, const String& originalURL, const KURL& finalURL, const CSSParserContext& context)
</span><span class="cx"> : m_ownerRule(ownerRule)
</span><span class="cx"> , m_originalURL(originalURL)
</span></span></pre></div>
<a id="trunkSourceWebCorecssCSSStyleSheeth"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/css/CSSStyleSheet.h (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/css/CSSStyleSheet.h 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/css/CSSStyleSheet.h 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -127,6 +127,8 @@
</span><span class="cx"> unsigned ruleCount() const;
</span><span class="cx">
</span><span class="cx"> bool usesRemUnits() const { return m_usesRemUnits; }
</span><ins>+
+ unsigned estimatedSizeInBytes() const;
</ins><span class="cx">
</span><span class="cx"> bool wrapperInsertRule(PassRefPtr<StyleRuleBase>, unsigned index);
</span><span class="cx"> void wrapperDeleteRule(unsigned index);
</span></span></pre></div>
<a id="trunkSourceWebCorecssStylePropertySetcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/css/StylePropertySet.cpp (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/css/StylePropertySet.cpp 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/css/StylePropertySet.cpp 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -1000,6 +1000,13 @@
</span><span class="cx"> propertySetCSSOMWrapperMap().get(this)->clearParentElement();
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+unsigned StylePropertySet::averageSizeInBytes()
+{
+ // Please update this if the storage scheme changes so that this longer reflects the actual size.
+ return sizeof(StylePropertySet);
+}
+
+// See the function above if you need to update this.
</ins><span class="cx"> class SameSizeAsStylePropertySet : public RefCounted<SameSizeAsStylePropertySet> {
</span><span class="cx"> Vector<CSSProperty, 4> properties;
</span><span class="cx"> unsigned bitfield;
</span></span></pre></div>
<a id="trunkSourceWebCorecssStylePropertySeth"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/css/StylePropertySet.h (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/css/StylePropertySet.h 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/css/StylePropertySet.h 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -113,6 +113,8 @@
</span><span class="cx"> // FIXME: Expand the concept of mutable/immutable StylePropertySet.
</span><span class="cx"> bool isMutable() const { return m_ownsCSSOMWrapper; }
</span><span class="cx">
</span><ins>+ static unsigned averageSizeInBytes();
+
</ins><span class="cx"> private:
</span><span class="cx"> StylePropertySet(CSSParserMode);
</span><span class="cx"> StylePropertySet(const Vector<CSSProperty>&);
</span></span></pre></div>
<a id="trunkSourceWebCorecssStyleRulecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/css/StyleRule.cpp (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/css/StyleRule.cpp 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/css/StyleRule.cpp 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -143,6 +143,11 @@
</span><span class="cx"> return rule.release();
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+unsigned StyleRule::averageSizeInBytes()
+{
+ return sizeof(StyleRule) + StylePropertySet::averageSizeInBytes();
+}
+
</ins><span class="cx"> StyleRule::StyleRule(int sourceLine)
</span><span class="cx"> : StyleRuleBase(Style, sourceLine)
</span><span class="cx"> {
</span></span></pre></div>
<a id="trunkSourceWebCorecssStyleRuleh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/css/StyleRule.h (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/css/StyleRule.h 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/css/StyleRule.h 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -102,6 +102,8 @@
</span><span class="cx">
</span><span class="cx"> PassRefPtr<StyleRule> copy() const { return adoptRef(new StyleRule(*this)); }
</span><span class="cx">
</span><ins>+ static unsigned averageSizeInBytes();
+
</ins><span class="cx"> private:
</span><span class="cx"> StyleRule(int sourceLine);
</span><span class="cx"> StyleRule(const StyleRule&);
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlHTMLLinkElementcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/HTMLLinkElement.cpp (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/HTMLLinkElement.cpp 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/html/HTMLLinkElement.cpp 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -295,6 +295,23 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> CSSParserContext parserContext(document(), baseURL, charset);
</span><ins>+
+ if (RefPtr<StyleSheetInternal> restoredSheet = const_cast<CachedCSSStyleSheet*>(cachedStyleSheet)->restoreParsedStyleSheet(parserContext)) {
+ ASSERT(restoredSheet->isCacheable());
+ ASSERT(!restoredSheet->isLoading());
+
+ // restoreParsedStyleSheet() currently returns a copy so it is ok to mutate the queries and the title like this.
+ RefPtr<MediaQuerySet> media = MediaQuerySet::createAllowingDescriptionSyntax(m_media);
+ restoredSheet->setMediaQueries(media.release());
+ restoredSheet->setTitle(title());
+
+ m_sheet = CSSStyleSheet::create(restoredSheet, this);
+ m_loading = false;
+ sheetLoaded();
+ notifyLoadedSheetAndAllCriticalSubresources(false);
+ return;
+ }
+
</ins><span class="cx"> RefPtr<StyleSheetInternal> styleSheet = StyleSheetInternal::create(href, baseURL, parserContext);
</span><span class="cx"> m_sheet = CSSStyleSheet::create(styleSheet, this);
</span><span class="cx">
</span><span class="lines">@@ -307,6 +324,9 @@
</span><span class="cx"> m_loading = false;
</span><span class="cx"> styleSheet->notifyLoadedSheet(cachedStyleSheet);
</span><span class="cx"> styleSheet->checkLoaded();
</span><ins>+
+ if (styleSheet->isCacheable())
+ const_cast<CachedCSSStyleSheet*>(cachedStyleSheet)->saveParsedStyleSheet(styleSheet);
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> bool HTMLLinkElement::styleSheetIsLoading() const
</span></span></pre></div>
<a id="trunkSourceWebCoreloadercacheCachedCSSStyleSheetcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/loader/cache/CachedCSSStyleSheet.cpp (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/loader/cache/CachedCSSStyleSheet.cpp 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/loader/cache/CachedCSSStyleSheet.cpp 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -27,12 +27,14 @@
</span><span class="cx"> #include "config.h"
</span><span class="cx"> #include "CachedCSSStyleSheet.h"
</span><span class="cx">
</span><del>-#include "MemoryCache.h"
</del><ins>+#include "CSSStyleSheet.h"
</ins><span class="cx"> #include "CachedResourceClientWalker.h"
</span><span class="cx"> #include "CachedStyleSheetClient.h"
</span><span class="cx"> #include "HTTPParsers.h"
</span><ins>+#include "MemoryCache.h"
+#include "SharedBuffer.h"
</ins><span class="cx"> #include "TextResourceDecoder.h"
</span><del>-#include "SharedBuffer.h"
</del><ins>+#include <wtf/CurrentTime.h>
</ins><span class="cx"> #include <wtf/Vector.h>
</span><span class="cx">
</span><span class="cx"> namespace WebCore {
</span><span class="lines">@@ -148,5 +150,38 @@
</span><span class="cx"> return true;
</span><span class="cx"> return typeOK;
</span><span class="cx"> }
</span><del>-
</del><ins>+
+void CachedCSSStyleSheet::destroyDecodedData()
+{
+ m_parsedStyleSheetCache.clear();
+ setDecodedSize(0);
</ins><span class="cx"> }
</span><ins>+
+PassRefPtr<StyleSheetInternal> CachedCSSStyleSheet::restoreParsedStyleSheet(const CSSParserContext& context)
+{
+ if (!m_parsedStyleSheetCache)
+ return 0;
+ // Cached parsed stylesheet has mutated, kick it out.
+ if (!m_parsedStyleSheetCache->isCacheable()) {
+ m_parsedStyleSheetCache.clear();
+ setDecodedSize(0);
+ return 0;
+ }
+ // Contexts must be identical so we know we would get the same exact result if we parsed again.
+ if (m_parsedStyleSheetCache->parserContext() != context)
+ return 0;
+
+ didAccessDecodedData(currentTime());
+ // FIXME: Implement copy-on-write to avoid copying when not necessary.
+ return m_parsedStyleSheetCache->copy();
+}
+
+void CachedCSSStyleSheet::saveParsedStyleSheet(PassRefPtr<StyleSheetInternal> sheet)
+{
+ ASSERT(sheet && sheet->isCacheable());
+ m_parsedStyleSheetCache = sheet;
+
+ setDecodedSize(m_parsedStyleSheetCache->estimatedSizeInBytes());
+}
+
+}
</ins></span></pre></div>
<a id="trunkSourceWebCoreloadercacheCachedCSSStyleSheeth"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/loader/cache/CachedCSSStyleSheet.h (115378 => 115379)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/loader/cache/CachedCSSStyleSheet.h 2012-04-26 22:25:35 UTC (rev 115378)
+++ trunk/Source/WebCore/loader/cache/CachedCSSStyleSheet.h 2012-04-26 22:26:35 UTC (rev 115379)
</span><span class="lines">@@ -33,7 +33,9 @@
</span><span class="cx">
</span><span class="cx"> class CachedResourceClient;
</span><span class="cx"> class SharedBuffer;
</span><ins>+ class StyleSheetInternal;
</ins><span class="cx"> class TextResourceDecoder;
</span><ins>+ struct CSSParserContext;
</ins><span class="cx">
</span><span class="cx"> class CachedCSSStyleSheet : public CachedResource {
</span><span class="cx"> public:
</span><span class="lines">@@ -51,7 +53,12 @@
</span><span class="cx"> virtual void data(PassRefPtr<SharedBuffer> data, bool allDataReceived);
</span><span class="cx"> virtual void error(CachedResource::Status);
</span><span class="cx">
</span><ins>+ virtual void destroyDecodedData() OVERRIDE;
+
</ins><span class="cx"> void checkNotify();
</span><ins>+
+ PassRefPtr<StyleSheetInternal> restoreParsedStyleSheet(const CSSParserContext&);
+ void saveParsedStyleSheet(PassRefPtr<StyleSheetInternal>);
</ins><span class="cx">
</span><span class="cx"> private:
</span><span class="cx"> bool canUseSheet(bool enforceMIMEType, bool* hasValidMIMEType) const;
</span><span class="lines">@@ -60,6 +67,8 @@
</span><span class="cx"> protected:
</span><span class="cx"> RefPtr<TextResourceDecoder> m_decoder;
</span><span class="cx"> String m_decodedSheetText;
</span><ins>+
+ RefPtr<StyleSheetInternal> m_parsedStyleSheetCache;
</ins><span class="cx"> };
</span><span class="cx">
</span><span class="cx"> }
</span></span></pre>
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