Changeset 196217 in webkit

Timestamp:

Feb 6, 2016 9:00:30 AM (8 years ago)

Author:

akling@apple.com

Message:

[iOS] Throw away linked code when navigating to a new page.
<​https://webkit.org/b/153851>

Reviewed by Gavin Barraclough.

Source/JavaScriptCore:

Add a VM API for throwing away linked code only.

• runtime/VM.cpp:

(JSC::VM::deleteAllLinkedCode):

• runtime/VM.h:

Source/WebCore:

When navigating to a new page, tell JSC to throw out any linked code it has lying around.
Linked code is tied to a specific global object, and as we're creating a new one for the
new page, none of it is useful to us here.

In the event that the user navigates back, the cost of relinking some code will be far
lower than the memory cost of keeping all of it around.

This landed previously but was rolled out due to a Speedometer regression. I've made one
minor but important change here: only throw away code if we're navigating away from an
existing history item. Or in other words, don't throw away code for "force peeks" or any
other navigations that are not traditional top-level main frame navigations.

• bindings/js/GCController.cpp:

(WebCore::GCController::deleteAllLinkedCode):

• bindings/js/GCController.h:
• loader/FrameLoader.cpp:

(WebCore::FrameLoader::commitProvisionalLoad):

Location:

trunk/Source

Files:

• JavaScriptCore/ChangeLog (modified) (1 diff)
• JavaScriptCore/runtime/VM.cpp (modified) (1 diff)
• JavaScriptCore/runtime/VM.h (modified) (1 diff)
• WebCore/ChangeLog (modified) (1 diff)
• WebCore/bindings/js/GCController.cpp (modified) (1 diff)
• WebCore/bindings/js/GCController.h (modified) (1 diff)
• WebCore/loader/FrameLoader.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2016-02-06  Andreas Kling  <akling@apple.com>
+
+        [iOS] Throw away linked code when navigating to a new page.
+        <https://webkit.org/b/153851>
+
+        Reviewed by Gavin Barraclough.
+
+        Add a VM API for throwing away linked code only.
+
+        * runtime/VM.cpp:
+        (JSC::VM::deleteAllLinkedCode):
+        * runtime/VM.h:
+
 2016-02-06  Commit Queue  <commit-queue@webkit.org>
 

trunk/Source/JavaScriptCore/runtime/VM.cpp

@@ -543 +543 @@
 }
 
+void VM::deleteAllLinkedCode()
+{
+    whenIdle([this]() {
+        heap.deleteAllCodeBlocks();
+        heap.reportAbandonedObjectGraph();
+    });
+}
+
 void VM::deleteAllCode()
 {

trunk/Source/JavaScriptCore/runtime/VM.h

@@ -575 +575 @@
 
     JS_EXPORT_PRIVATE void deleteAllCode();
+    JS_EXPORT_PRIVATE void deleteAllLinkedCode();
 
     void registerWatchpointForImpureProperty(const Identifier&, Watchpoint*);

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2016-02-06  Andreas Kling  <akling@apple.com>
+
+        [iOS] Throw away linked code when navigating to a new page.
+        <https://webkit.org/b/153851>
+
+        Reviewed by Gavin Barraclough.
+
+        When navigating to a new page, tell JSC to throw out any linked code it has lying around.
+        Linked code is tied to a specific global object, and as we're creating a new one for the
+        new page, none of it is useful to us here.
+
+        In the event that the user navigates back, the cost of relinking some code will be far
+        lower than the memory cost of keeping all of it around.
+
+        This landed previously but was rolled out due to a Speedometer regression. I've made one
+        minor but important change here: only throw away code if we're navigating away from an
+        existing history item. Or in other words, don't throw away code for "force peeks" or any
+        other navigations that are not traditional top-level main frame navigations.
+
+        * bindings/js/GCController.cpp:
+        (WebCore::GCController::deleteAllLinkedCode):
+        * bindings/js/GCController.h:
+        * loader/FrameLoader.cpp:
+        (WebCore::FrameLoader::commitProvisionalLoad):
+
 2016-02-06  Konstantin Tokarev  <annulen@yandex.ru>
 

trunk/Source/WebCore/bindings/js/GCController.cpp

@@ -123 +123 @@
 }
 
+void GCController::deleteAllLinkedCode()
+{
+    JSLockHolder lock(JSDOMWindow::commonVM());
+    JSDOMWindow::commonVM().deleteAllLinkedCode();
+}
+
 } // namespace WebCore

trunk/Source/WebCore/bindings/js/GCController.h

@@ -47 +47 @@
     WEBCORE_EXPORT void setJavaScriptGarbageCollectorTimerEnabled(bool);
     WEBCORE_EXPORT void deleteAllCode();
+    WEBCORE_EXPORT void deleteAllLinkedCode();
 
 private:

trunk/Source/WebCore/loader/FrameLoader.cpp

@@ -67 +67 @@
 #include "FrameTree.h"
 #include "FrameView.h"
+#include "GCController.h"
 #include "HTMLAnchorElement.h"
 #include "HTMLFormElement.h"
@@ -1757 +1758 @@
     willTransitionToCommitted();
 
-    // Check to see if we need to cache the page we are navigating away from into the back/forward cache.
-    // We are doing this here because we know for sure that a new page is about to be loaded.
-    if (!m_frame.tree().parent() && history().currentItem())
+    if (!m_frame.tree().parent() && history().currentItem()) {
+        // Check to see if we need to cache the page we are navigating away from into the back/forward cache.
+        // We are doing this here because we know for sure that a new page is about to be loaded.
         PageCache::singleton().addIfCacheable(*history().currentItem(), m_frame.page());
+
+#if PLATFORM(IOS)
+        // For top-level navigations, have JSC throw away linked code. The immediate memory savings far
+        // outweigh the cost of recompiling in the case of a future backwards navigation.
+        GCController::singleton().deleteAllLinkedCode();
+#endif
+    }
 
     if (m_loadType != FrameLoadType::Replace)