From e3c7499467db96eb1bc67936fb8e5cbf89799e54 Mon Sep 17 00:00:00 2001 From: "dbaron%dbaron.org" Date: Thu, 5 Jul 2007 22:20:16 +0000 Subject: [PATCH] In ExplainLiveExpectedGarbage, print only the externally-referenced nodes from which the expected garbage is reachable. b=387005 r=graydon --- xpcom/base/nsCycleCollector.cpp | 161 ++++++++++++++++++++++++++------ 1 file changed, 133 insertions(+), 28 deletions(-) diff --git a/xpcom/base/nsCycleCollector.cpp b/xpcom/base/nsCycleCollector.cpp index d3e44599101..37ccaa315df 100644 --- a/xpcom/base/nsCycleCollector.cpp +++ b/xpcom/base/nsCycleCollector.cpp @@ -414,6 +414,15 @@ public: }; +#ifdef DEBUG_CC + +struct ReversedEdge { + PtrInfo *mTarget; + ReversedEdge *mNext; +}; + +#endif + enum NodeColor { black, white, grey }; @@ -435,7 +444,14 @@ struct PtrInfo #ifdef DEBUG_CC size_t mBytes; char *mName; + + // For finding roots in ExplainLiveExpectedGarbage (when there are + // missing calls to suspect or failures to unlink). PRUint32 mSCCIndex; // strongly connected component + + // For finding roots in ExplainLiveExpectedGarbage (when nodes + // expected to be garbage are black). + ReversedEdge* mReversedEdges; // linked list #endif PtrInfo(void *aPointer, nsCycleCollectionParticipant *aParticipant) @@ -450,7 +466,8 @@ struct PtrInfo #ifdef DEBUG_CC , mBytes(0), mName(nsnull), - mSCCIndex(0) + mSCCIndex(0), + mReversedEdges(nsnull) #endif { } @@ -581,6 +598,9 @@ struct GCGraph NodePool mNodes; EdgePool mEdges; PRUint32 mRootCount; +#ifdef DEBUG_CC + ReversedEdge *mReversedEdges; +#endif GCGraph() : mRootCount(0) { sCurrGraph = this; @@ -847,7 +867,10 @@ struct nsCycleCollector FILE *mPtrLog; void MaybeDrawGraphs(GCGraph &graph); + void ExplainLiveExpectedGarbage(); + PRBool CreateReversedEdges(GCGraph &graph); + void DestroyReversedEdges(GCGraph &graph); void ShouldBeFreed(nsISupports *n); void WasFreed(nsISupports *n); PointerSet mExpectedGarbage; @@ -2112,6 +2135,9 @@ nsCycleCollector::Collect(PRUint32 aTryCollections) printf("cc: Collect() took %lldms\n", (PR_Now() - start) / PR_USEC_PER_MSEC); #endif +#ifdef DEBUG_CC + ExplainLiveExpectedGarbage(); +#endif } void @@ -2130,8 +2156,6 @@ nsCycleCollector::Shutdown() printf("Might have been able to release more cycles if the cycle collector would " "run once more at shutdown.\n"); } - - ExplainLiveExpectedGarbage(); #endif mParams.mDoNothing = PR_TRUE; } @@ -2194,7 +2218,7 @@ nsCycleCollector::ExplainLiveExpectedGarbage() mScanInProgress = PR_FALSE; - PRBool giveKnownReferences = PR_FALSE; + PRBool describeExtraRefcounts = PR_FALSE; PRBool findCycleRoots = PR_FALSE; { NodePool::Enumerator queue(graph.mNodes); @@ -2205,34 +2229,62 @@ nsCycleCollector::ExplainLiveExpectedGarbage() } if (pi->mInternalRefs != pi->mRefCount) { - // Note that the external references may have been external - // to a different node in the cycle collection that just - // happened, if that different node was purple and then - // black. - printf("nsCycleCollector: %s %p was not collected due to %d\n" - " external references\n", - pi->mName, pi->mPointer, - pi->mRefCount - pi->mInternalRefs); - giveKnownReferences = PR_TRUE; + describeExtraRefcounts = PR_TRUE; } } } - if (giveKnownReferences) { - printf("The known references to the objects above not collected\n" - "due to external references are:\n"); - NodePool::Enumerator queue(graph.mNodes); - while (!queue.IsDone()) { - PtrInfo *pi = queue.GetNext(); - for (EdgePool::Iterator child = pi->mFirstChild, - child_end = pi->mLastChild; - child != child_end; ++child) { - if ((*child)->mInternalRefs != (*child)->mRefCount) { - printf(" to: %p from %s %p\n", - (*child)->mPointer, pi->mName, pi->mPointer); + if (describeExtraRefcounts && CreateReversedEdges(graph)) { + // Note that the external references may have been external + // to a different node in the cycle collection that just + // happened, if that different node was purple and then + // black. + + // Use mSCCIndex temporarily to track whether we've reached + // nodes in the breadth-first search. + const PRUint32 INDEX_UNREACHED = 0; + const PRUint32 INDEX_REACHED = 1; + NodePool::Enumerator etor_clear(graph.mNodes); + while (!etor_clear.IsDone()) { + PtrInfo *pi = etor_clear.GetNext(); + pi->mSCCIndex = INDEX_UNREACHED; + } + + nsDeque queue; // for breadth-first search + NodePool::Enumerator etor_roots(graph.mNodes); + for (PRUint32 i = 0; i < graph.mRootCount; ++i) { + PtrInfo *root_pi = etor_roots.GetNext(); + root_pi->mSCCIndex = INDEX_REACHED; + queue.Push(root_pi); + } + + while (queue.GetSize() > 0) { + PtrInfo *pi = (PtrInfo*)queue.PopFront(); + for (ReversedEdge *e = pi->mReversedEdges; e; e = e->mNext) { + if (e->mTarget->mSCCIndex == INDEX_UNREACHED) { + e->mTarget->mSCCIndex = INDEX_REACHED; + queue.Push(e->mTarget); + } + } + + if (pi->mInternalRefs != pi->mRefCount) { + printf("nsCycleCollector: %s %p was not collected due " + "to %d\n" + " external references (%d total - %d known)\n", + pi->mName, pi->mPointer, + pi->mRefCount - pi->mInternalRefs, + pi->mRefCount, pi->mInternalRefs); + printf(" The %d known references to it were from:\n", + pi->mInternalRefs); + for (ReversedEdge *e = pi->mReversedEdges; + e; e = e->mNext) { + printf(" %s %p\n", + e->mTarget->mName, e->mTarget->mPointer); } } } + + DestroyReversedEdges(graph); } if (findCycleRoots) { @@ -2246,7 +2298,7 @@ nsCycleCollector::ExplainLiveExpectedGarbage() { // Use mSCCIndex temporarily to track the DFS numbering: const PRUint32 INDEX_UNREACHED = 0; - const PRUint32 INDEX_REACHED = 1; + const PRUint32 INDEX_TRAVERSING = 1; const PRUint32 INDEX_NUMBERED = 2; NodePool::Enumerator etor_clear(graph.mNodes); @@ -2266,7 +2318,7 @@ nsCycleCollector::ExplainLiveExpectedGarbage() while (stack.GetSize() > 0) { PtrInfo *pi = (PtrInfo*)stack.Peek(); if (pi->mSCCIndex == INDEX_UNREACHED) { - pi->mSCCIndex = INDEX_REACHED; + pi->mSCCIndex = INDEX_TRAVERSING; for (EdgePool::Iterator child = pi->mFirstChild, child_end = pi->mLastChild; child != child_end; ++child) { @@ -2276,7 +2328,10 @@ nsCycleCollector::ExplainLiveExpectedGarbage() stack.Pop(); // Somebody else might have numbered it already // (since this is depth-first, not breadth-first). - if (pi->mSCCIndex == INDEX_REACHED) { + // This happens if a node is pushed on the stack + // a second time while it is on the stack in + // UNREACHED state. + if (pi->mSCCIndex == INDEX_TRAVERSING) { pi->mSCCIndex = INDEX_NUMBERED; DFSPostOrder.Push(pi); } @@ -2341,6 +2396,56 @@ nsCycleCollector::ExplainLiveExpectedGarbage() } } +PRBool +nsCycleCollector::CreateReversedEdges(GCGraph &graph) +{ + // Count the edges in the graph. + PRUint32 edgeCount = 0; + NodePool::Enumerator countQueue(graph.mNodes); + while (!countQueue.IsDone()) { + PtrInfo *pi = countQueue.GetNext(); + for (EdgePool::Iterator e = pi->mFirstChild, e_end = pi->mLastChild; + e != e_end; ++e, ++edgeCount) { + } + } + + // Allocate a pool to hold all of the edges. + graph.mReversedEdges = new ReversedEdge[edgeCount]; + if (graph.mReversedEdges == nsnull) { + NS_NOTREACHED("allocation failure creating reversed edges"); + return PR_FALSE; + } + + // Fill in the reversed edges by scanning all forward edges. + ReversedEdge *current = graph.mReversedEdges; + NodePool::Enumerator buildQueue(graph.mNodes); + while (!buildQueue.IsDone()) { + PtrInfo *pi = buildQueue.GetNext(); + for (EdgePool::Iterator e = pi->mFirstChild, e_end = pi->mLastChild; + e != e_end; ++e) { + current->mTarget = pi; + current->mNext = (*e)->mReversedEdges; + (*e)->mReversedEdges = current; + ++current; + } + } + NS_ASSERTION(current - graph.mReversedEdges == edgeCount, "misallocation"); + return PR_TRUE; +} + +void +nsCycleCollector::DestroyReversedEdges(GCGraph &graph) +{ + NodePool::Enumerator queue(graph.mNodes); + while (!queue.IsDone()) { + PtrInfo *pi = queue.GetNext(); + pi->mReversedEdges = nsnull; + } + + delete graph.mReversedEdges; + graph.mReversedEdges = nsnull; +} + void nsCycleCollector::ShouldBeFreed(nsISupports *n) {