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Bug 882162: Part 8 - Move the rest of nsCycleCollectionJSRuntime's implementation into mozilla::CycleCollectedJSRuntime. r=mccr8

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This commit is contained in:
Kyle Huey 2013-06-18 12:02:16 -07:00
parent 213c4bdde8
commit 9ad3187e9b
4 changed files with 90 additions and 76 deletions
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76
js/xpconnect/src/nsXPConnect.cpp
View File

@ -248,55 +248,7 @@ nsXPConnect::NeedCollect()
void
nsXPConnect::Collect(uint32_t reason)
{
// We're dividing JS objects into 2 categories:
//
// 1. "real" roots, held by the JS engine itself or rooted through the root
// and lock JS APIs. Roots from this category are considered black in the
// cycle collector, any cycle they participate in is uncollectable.
//
// 2. roots held by C++ objects that participate in cycle collection,
// held by XPConnect (see XPCJSRuntime::TraceXPConnectRoots). Roots from
// this category are considered grey in the cycle collector, their final
// color depends on the objects that hold them.
//
// Note that if a root is in both categories it is the fact that it is in
// category 1 that takes precedence, so it will be considered black.
//
// During garbage collection we switch to an additional mark color (gray)
// when tracing inside TraceXPConnectRoots. This allows us to walk those
// roots later on and add all objects reachable only from them to the
// cycle collector.
//
// Phases:
//
// 1. marking of the roots in category 1 by having the JS GC do its marking
// 2. marking of the roots in category 2 by XPCJSRuntime::TraceXPConnectRoots
// using an additional color (gray).
// 3. end of GC, GC can sweep its heap
//
// At some later point, when the cycle collector runs:
//
// 4. walk gray objects and add them to the cycle collector, cycle collect
//
// JS objects that are part of cycles the cycle collector breaks will be
// collected by the next JS.
//
// If WantAllTraces() is false the cycle collector will not traverse roots
// from category 1 or any JS objects held by them. Any JS objects they hold
// will already be marked by the JS GC and will thus be colored black
// themselves. Any C++ objects they hold will have a missing (untraversed)
// edge from the JS object to the C++ object and so it will be marked black
// too. This decreases the number of objects that the cycle collector has to
// deal with.
// To improve debugging, if WantAllTraces() is true all JS objects are
// traversed.
MOZ_ASSERT(reason < JS::gcreason::NUM_REASONS);
JS::gcreason::Reason gcreason = (JS::gcreason::Reason)reason;
JSRuntime *rt = GetRuntime()->Runtime();
JS::PrepareForFullGC(rt);
JS::GCForReason(rt, gcreason);
return GetRuntime()->Collect(reason);
}
NS_IMETHODIMP
@ -342,34 +294,10 @@ nsXPConnect::NotifyEnterMainThread()
mRuntime->NotifyEnterMainThread();
}
/*
* Return true if there exists a JSContext with a default global whose current
* inner is gray. The intent is to look for JS Object windows. We don't merge
* system compartments, so we don't use them to trigger merging CCs.
*/
bool
nsXPConnect::UsefulToMergeZones()
{
JSContext *iter = nullptr;
JSContext *cx;
while ((cx = JS_ContextIterator(GetRuntime()->Runtime(), &iter))) {
// Skip anything without an nsIScriptContext, as well as any scx whose
// NativeGlobal() is not an outer window (this happens with XUL Prototype
// compilation scopes, for example, which we're not interested in).
nsIScriptContext *scx = GetScriptContextFromJSContext(cx);
JS::RootedObject global(cx, scx ? scx->GetNativeGlobal() : nullptr);
if (!global || !js::GetObjectParent(global)) {
continue;
}
// Grab the inner from the outer.
global = JS_ObjectToInnerObject(cx, global);
MOZ_ASSERT(!js::GetObjectParent(global));
if (JS::GCThingIsMarkedGray(global) &&
!js::IsSystemCompartment(js::GetObjectCompartment(global))) {
return true;
}
}
return false;
return GetRuntime()->UsefulToMergeZones();
}
nsCycleCollectionParticipant *

4
js/xpconnect/src/xpcprivate.h
View File

@ -507,10 +507,10 @@ public:
virtual void NotifyEnterMainThread(); // DONE
virtual nsresult BeginCycleCollection(nsCycleCollectionNoteRootCallback &cb); // DONE
virtual nsCycleCollectionParticipant *GetParticipant(); // DONE
virtual bool UsefulToMergeZones();
virtual bool UsefulToMergeZones(); // DONE
virtual void FixWeakMappingGrayBits(); // DONE
virtual bool NeedCollect(); // DONE
virtual void Collect(uint32_t reason);
virtual void Collect(uint32_t reason); // DONE
// This returns the singleton nsCycleCollectionParticipant for JSContexts.
static nsCycleCollectionParticipant *JSContextParticipant();

84
xpcom/base/CycleCollectedJSRuntime.cpp
View File

@ -11,6 +11,7 @@
#include "jsprf.h"
#include "nsCycleCollectionNoteRootCallback.h"
#include "nsCycleCollectionParticipant.h"
#include "nsDOMJSUtils.h"
#include "nsLayoutStatics.h"
#include "xpcpublic.h"
@ -829,6 +830,36 @@ CycleCollectedJSRuntime::BeginCycleCollection(nsCycleCollectionNoteRootCallback
return NS_OK;
}
/*
* Return true if there exists a JSContext with a default global whose current
* inner is gray. The intent is to look for JS Object windows. We don't merge
* system compartments, so we don't use them to trigger merging CCs.
*/
bool
CycleCollectedJSRuntime::UsefulToMergeZones() const
{
JSContext* iter = nullptr;
JSContext* cx;
while ((cx = JS_ContextIterator(mJSRuntime, &iter))) {
// Skip anything without an nsIScriptContext, as well as any scx whose
// NativeGlobal() is not an outer window (this happens with XUL Prototype
// compilation scopes, for example, which we're not interested in).
nsIScriptContext* scx = GetScriptContextFromJSContext(cx);
JS::RootedObject global(cx, scx ? scx->GetNativeGlobal() : nullptr);
if (!global || !js::GetObjectParent(global)) {
continue;
}
// Grab the inner from the outer.
global = JS_ObjectToInnerObject(cx, global);
MOZ_ASSERT(!js::GetObjectParent(global));
if (JS::GCThingIsMarkedGray(global) &&
!js::IsSystemCompartment(js::GetObjectCompartment(global))) {
return true;
}
}
return false;
}
void
CycleCollectedJSRuntime::FixWeakMappingGrayBits() const
{
@ -841,3 +872,56 @@ CycleCollectedJSRuntime::NeedCollect() const
{
return !js::AreGCGrayBitsValid(mJSRuntime);
}
void
CycleCollectedJSRuntime::Collect(uint32_t aReason) const
{
// We're dividing JS objects into 2 categories:
//
// 1. "real" roots, held by the JS engine itself or rooted through the root
// and lock JS APIs. Roots from this category are considered black in the
// cycle collector, any cycle they participate in is uncollectable.
//
// 2. roots held by C++ objects that participate in cycle collection,
// held by XPConnect (see TraceXPConnectRoots). Roots from this category
// are considered grey in the cycle collector, their final color depends
// on the objects that hold them.
//
// Note that if a root is in both categories it is the fact that it is in
// category 1 that takes precedence, so it will be considered black.
//
// During garbage collection we switch to an additional mark color (gray)
// when tracing inside TraceNativeRoots. This allows us to walk those
// roots later on and add all objects reachable only from them to the
// cycle collector.
//
// Phases:
//
// 1. marking of the roots in category 1 by having the JS GC do its marking
// 2. marking of the roots in category 2 by TraceNativeRoots using an
// additional color (gray).
// 3. end of GC, GC can sweep its heap
//
// At some later point, when the cycle collector runs:
//
// 4. walk gray objects and add them to the cycle collector, cycle collect
//
// JS objects that are part of cycles the cycle collector breaks will be
// collected by the next JS.
//
// If WantAllTraces() is false the cycle collector will not traverse roots
// from category 1 or any JS objects held by them. Any JS objects they hold
// will already be marked by the JS GC and will thus be colored black
// themselves. Any C++ objects they hold will have a missing (untraversed)
// edge from the JS object to the C++ object and so it will be marked black
// too. This decreases the number of objects that the cycle collector has to
// deal with.
// To improve debugging, if WantAllTraces() is true all JS objects are
// traversed.
MOZ_ASSERT(aReason < JS::gcreason::NUM_REASONS);
JS::gcreason::Reason gcreason = static_cast<JS::gcreason::Reason>(aReason);
JS::PrepareForFullGC(mJSRuntime);
JS::GCForReason(mJSRuntime, gcreason);
}

2
xpcom/base/CycleCollectedJSRuntime.h
View File

@ -160,8 +160,10 @@ public:
void NotifyLeaveCycleCollectionThread() const;
void NotifyEnterMainThread() const;
nsresult BeginCycleCollection(nsCycleCollectionNoteRootCallback &aCb);
bool UsefulToMergeZones() const;
void FixWeakMappingGrayBits() const;
bool NeedCollect() const;
void Collect(uint32_t reason) const;
// XXXkhuey should be private
protected: