/*
* Return unused memory to the system if possible.
*/
static void trimHeaps()
{
HS_BOILERPLATE();
HeapSource *hs = gHs;
size_t heapBytes = 0;
for (size_t i = 0; i < hs->numHeaps; i++) {
Heap *heap = &hs->heaps[i];
/* Return the wilderness chunk to the system.
*/
mspace_trim(heap->msp, 0);
/* Return any whole free pages to the system.
*/
mspace_walk_free_pages(heap->msp, releasePagesInRange, &heapBytes);
}
/* Same for the native heap.
*/
dlmalloc_trim(0);
size_t nativeBytes = 0;
dlmalloc_walk_free_pages(releasePagesInRange, &nativeBytes);
LOGD_HEAP("madvised %zd (GC) + %zd (native) = %zd total bytes",
heapBytes, nativeBytes, heapBytes + nativeBytes);
}
/*
* Sets concurrentStart
*/
void dvmSetTargetHeapConcurrentStart(size_t size)
{
HS_BOILERPLATE();
concurrentStart = size;
LOGD_HEAP("dvmSetTargetHeapConcurrentStart %d", size );
}
/*
* Gets concurrentStart
*/
int dvmGetTargetHeapConcurrentStart()
{
HS_BOILERPLATE();
LOGD_HEAP("dvmGetTargetHeapConcurrentStart %d", concurrentStart );
return concurrentStart;
}
/*
* Gets heapIdeaFree
*/
int dvmGetTargetHeapIdealFree()
{
HS_BOILERPLATE();
LOGD_HEAP("dvmGetTargetHeapIdealFree %d", heapIdeaFree );
return heapIdeaFree;
}
/*
* Sets heapIdeaFree
*/
void dvmSetTargetHeapIdealFree(size_t size)
{
HS_BOILERPLATE();
heapIdeaFree = size;
LOGD_HEAP("dvmSetTargetHeapIdealFree %d", size );
}
/*
* Initiate garbage collection.
*
* NOTES:
* - If we don't hold gDvm.threadListLock, it's possible for a thread to
* be added to the thread list while we work. The thread should NOT
* start executing, so this is only interesting when we start chasing
* thread stacks. (Before we do so, grab the lock.)
*
* We are not allowed to GC when the debugger has suspended the VM, which
* is awkward because debugger requests can cause allocations. The easiest
* way to enforce this is to refuse to GC on an allocation made by the
* JDWP thread -- we have to expand the heap or fail.
*/
void dvmCollectGarbageInternal(const GcSpec* spec)
{
GcHeap *gcHeap = gDvm.gcHeap;
u4 gcEnd = 0;
u4 rootStart = 0 , rootEnd = 0;
u4 dirtyStart = 0, dirtyEnd = 0;
size_t numObjectsFreed, numBytesFreed;
size_t currAllocated, currFootprint;
size_t percentFree;
int oldThreadPriority = INT_MAX;
/* The heap lock must be held.
*/
if (gcHeap->gcRunning) {
LOGW_HEAP("Attempted recursive GC");
return;
}
gcHeap->gcRunning = true;
rootStart = dvmGetRelativeTimeMsec();
dvmSuspendAllThreads(SUSPEND_FOR_GC);
/*
* If we are not marking concurrently raise the priority of the
* thread performing the garbage collection.
*/
if (!spec->isConcurrent) {
oldThreadPriority = os_raiseThreadPriority();
}
if (gDvm.preVerify) {
LOGV_HEAP("Verifying roots and heap before GC");
verifyRootsAndHeap();
}
dvmMethodTraceGCBegin();
/* Set up the marking context.
*/
if (!dvmHeapBeginMarkStep(spec->isPartial)) {
LOGE_HEAP("dvmHeapBeginMarkStep failed; aborting");
dvmAbort();
}
/* Mark the set of objects that are strongly reachable from the roots.
*/
LOGD_HEAP("Marking...");
dvmHeapMarkRootSet();
/* dvmHeapScanMarkedObjects() will build the lists of known
* instances of the Reference classes.
*/
assert(gcHeap->softReferences == NULL);
assert(gcHeap->weakReferences == NULL);
assert(gcHeap->finalizerReferences == NULL);
assert(gcHeap->phantomReferences == NULL);
assert(gcHeap->clearedReferences == NULL);
if (spec->isConcurrent) {
/*
* Resume threads while tracing from the roots. We unlock the
* heap to allow mutator threads to allocate from free space.
*/
dvmClearCardTable();
dvmUnlockHeap();
dvmResumeAllThreads(SUSPEND_FOR_GC);
rootEnd = dvmGetRelativeTimeMsec();
}
/* Recursively mark any objects that marked objects point to strongly.
* If we're not collecting soft references, soft-reachable
* objects will also be marked.
*/
LOGD_HEAP("Recursing...");
dvmHeapScanMarkedObjects();
if (spec->isConcurrent) {
/*
* Re-acquire the heap lock and perform the final thread
* suspension.
*/
dirtyStart = dvmGetRelativeTimeMsec();
dvmLockHeap();
dvmSuspendAllThreads(SUSPEND_FOR_GC);
/*
* As no barrier intercepts root updates, we conservatively
* assume all roots may be gray and re-mark them.
*/
dvmHeapReMarkRootSet();
/*
* With the exception of reference objects and weak interned
* strings, all gray objects should now be on dirty cards.
*/
if (gDvm.verifyCardTable) {
dvmVerifyCardTable();
}
/*
* Recursively mark gray objects pointed to by the roots or by
* heap objects dirtied during the concurrent mark.
*/
dvmHeapReScanMarkedObjects();
}
/*
* All strongly-reachable objects have now been marked. Process
* weakly-reachable objects discovered while tracing.
*/
dvmHeapProcessReferences(&gcHeap->softReferences,
spec->doPreserve == false,
&gcHeap->weakReferences,
&gcHeap->finalizerReferences,
&gcHeap->phantomReferences);
#if defined(WITH_JIT)
/*
* Patching a chaining cell is very cheap as it only updates 4 words. It's
* the overhead of stopping all threads and synchronizing the I/D cache
* that makes it expensive.
*
* Therefore we batch those work orders in a queue and go through them
* when threads are suspended for GC.
*/
dvmCompilerPerformSafePointChecks();
#endif
LOGD_HEAP("Sweeping...");
dvmHeapSweepSystemWeaks();
/*
* Live objects have a bit set in the mark bitmap, swap the mark
* and live bitmaps. The sweep can proceed concurrently viewing
* the new live bitmap as the old mark bitmap, and vice versa.
*/
dvmHeapSourceSwapBitmaps();
if (gDvm.postVerify) {
LOGV_HEAP("Verifying roots and heap after GC");
verifyRootsAndHeap();
}
if (spec->isConcurrent) {
dvmUnlockHeap();
dvmResumeAllThreads(SUSPEND_FOR_GC);
dirtyEnd = dvmGetRelativeTimeMsec();
}
dvmHeapSweepUnmarkedObjects(spec->isPartial, spec->isConcurrent,
&numObjectsFreed, &numBytesFreed);
LOGD_HEAP("Cleaning up...");
dvmHeapFinishMarkStep();
if (spec->isConcurrent) {
dvmLockHeap();
}
LOGD_HEAP("Done.");
/* Now's a good time to adjust the heap size, since
* we know what our utilization is.
*
* This doesn't actually resize any memory;
* it just lets the heap grow more when necessary.
*/
dvmHeapSourceGrowForUtilization();
currAllocated = dvmHeapSourceGetValue(HS_BYTES_ALLOCATED, NULL, 0);
currFootprint = dvmHeapSourceGetValue(HS_FOOTPRINT, NULL, 0);
dvmMethodTraceGCEnd();
LOGV_HEAP("GC finished");
gcHeap->gcRunning = false;
LOGV_HEAP("Resuming threads");
if (spec->isConcurrent) {
/*
* Wake-up any threads that blocked after a failed allocation
* request.
*/
dvmBroadcastCond(&gDvm.gcHeapCond);
}
if (!spec->isConcurrent) {
dvmResumeAllThreads(SUSPEND_FOR_GC);
dirtyEnd = dvmGetRelativeTimeMsec();
/*
* Restore the original thread scheduling priority if it was
* changed at the start of the current garbage collection.
*/
if (oldThreadPriority != INT_MAX) {
os_lowerThreadPriority(oldThreadPriority);
}
}
/*
* Move queue of pending references back into Java.
*/
dvmEnqueueClearedReferences(&gDvm.gcHeap->clearedReferences);
gcEnd = dvmGetRelativeTimeMsec();
percentFree = 100 - (size_t)(100.0f * (float)currAllocated / currFootprint);
if (!spec->isConcurrent) {
u4 markSweepTime = dirtyEnd - rootStart;
u4 gcTime = gcEnd - rootStart;
bool isSmall = numBytesFreed > 0 && numBytesFreed < 1024;
ALOGD("%s freed %s%zdK, %d%% free %zdK/%zdK, paused %ums, total %ums",
spec->reason,
isSmall ? "<" : "",
numBytesFreed ? MAX(numBytesFreed / 1024, 1) : 0,
percentFree,
currAllocated / 1024, currFootprint / 1024,
markSweepTime, gcTime);
} else {
u4 rootTime = rootEnd - rootStart;
u4 dirtyTime = dirtyEnd - dirtyStart;
u4 gcTime = gcEnd - rootStart;
bool isSmall = numBytesFreed > 0 && numBytesFreed < 1024;
ALOGD("%s freed %s%zdK, %d%% free %zdK/%zdK, paused %ums+%ums, total %ums",
spec->reason,
isSmall ? "<" : "",
numBytesFreed ? MAX(numBytesFreed / 1024, 1) : 0,
percentFree,
currAllocated / 1024, currFootprint / 1024,
rootTime, dirtyTime, gcTime);
}
if (gcHeap->ddmHpifWhen != 0) {
LOGD_HEAP("Sending VM heap info to DDM");
dvmDdmSendHeapInfo(gcHeap->ddmHpifWhen, false);
}
if (gcHeap->ddmHpsgWhen != 0) {
LOGD_HEAP("Dumping VM heap to DDM");
dvmDdmSendHeapSegments(false, false);
}
if (gcHeap->ddmNhsgWhen != 0) {
LOGD_HEAP("Dumping native heap to DDM");
dvmDdmSendHeapSegments(false, true);
}
}
/* All objects for stronger reference levels have been
* marked before this is called.
*/
void dvmHeapHandleReferences(Object *refListHead, enum RefType refType)
{
Object *reference;
GcMarkContext *markContext = &gDvm.gcHeap->markContext;
const int offVmData = gDvm.offJavaLangRefReference_vmData;
const int offReferent = gDvm.offJavaLangRefReference_referent;
bool workRequired = false;
size_t numCleared = 0;
size_t numEnqueued = 0;
reference = refListHead;
while (reference != NULL) {
Object *next;
Object *referent;
/* Pull the interesting fields out of the Reference object.
*/
next = dvmGetFieldObject(reference, offVmData);
referent = dvmGetFieldObject(reference, offReferent);
//TODO: when handling REF_PHANTOM, unlink any references
// that fail this initial if(). We need to re-walk
// the list, and it would be nice to avoid the extra
// work.
if (referent != NULL && !isMarked(ptr2chunk(referent), markContext)) {
bool schedClear, schedEnqueue;
/* This is the strongest reference that refers to referent.
* Do the right thing.
*/
switch (refType) {
case REF_SOFT:
case REF_WEAK:
schedClear = clearReference(reference);
schedEnqueue = enqueueReference(reference);
break;
case REF_PHANTOM:
/* PhantomReferences are not cleared automatically.
* Until someone clears it (or the reference itself
* is collected), the referent must remain alive.
*
* It's necessary to fully mark the referent because
* it will still be present during the next GC, and
* all objects that it points to must be valid.
* (The referent will be marked outside of this loop,
* after handing all references of this strength, in
* case multiple references point to the same object.)
*/
schedClear = false;
/* A PhantomReference is only useful with a
* queue, but since it's possible to create one
* without a queue, we need to check.
*/
schedEnqueue = enqueueReference(reference);
break;
default:
assert(!"Bad reference type");
schedClear = false;
schedEnqueue = false;
break;
}
numCleared += schedClear ? 1 : 0;
numEnqueued += schedEnqueue ? 1 : 0;
if (schedClear || schedEnqueue) {
uintptr_t workBits;
/* Stuff the clear/enqueue bits in the bottom of
* the pointer. Assumes that objects are 8-byte
* aligned.
*
* Note that we are adding the *Reference* (which
* is by definition already marked at this point) to
* this list; we're not adding the referent (which
* has already been cleared).
*/
assert(((intptr_t)reference & 3) == 0);
assert(((WORKER_CLEAR | WORKER_ENQUEUE) & ~3) == 0);
workBits = (schedClear ? WORKER_CLEAR : 0) |
(schedEnqueue ? WORKER_ENQUEUE : 0);
if (!dvmHeapAddRefToLargeTable(
&gDvm.gcHeap->referenceOperations,
(Object *)((uintptr_t)reference | workBits)))
{
LOGE_HEAP("dvmMalloc(): no room for any more "
"reference operations\n");
dvmAbort();
}
workRequired = true;
}
if (refType != REF_PHANTOM) {
/* Let later GCs know not to reschedule this reference.
*/
dvmSetFieldObject(reference, offVmData,
SCHEDULED_REFERENCE_MAGIC);
} // else this is handled later for REF_PHANTOM
} // else there was a stronger reference to the referent.
reference = next;
}
#define refType2str(r) \
((r) == REF_SOFT ? "soft" : ( \
(r) == REF_WEAK ? "weak" : ( \
(r) == REF_PHANTOM ? "phantom" : "UNKNOWN" )))
LOGD_HEAP("dvmHeapHandleReferences(): cleared %zd, enqueued %zd %s references\n", numCleared, numEnqueued, refType2str(refType));
/* Walk though the reference list again, and mark any non-clear/marked
* referents. Only PhantomReferences can have non-clear referents
* at this point.
*/
if (refType == REF_PHANTOM) {
bool scanRequired = false;
HPROF_SET_GC_SCAN_STATE(HPROF_ROOT_REFERENCE_CLEANUP, 0);
reference = refListHead;
while (reference != NULL) {
Object *next;
Object *referent;
/* Pull the interesting fields out of the Reference object.
*/
next = dvmGetFieldObject(reference, offVmData);
referent = dvmGetFieldObject(reference, offReferent);
if (referent != NULL && !isMarked(ptr2chunk(referent), markContext)) {
markObjectNonNull(referent, markContext);
scanRequired = true;
/* Let later GCs know not to reschedule this reference.
*/
dvmSetFieldObject(reference, offVmData,
SCHEDULED_REFERENCE_MAGIC);
}
reference = next;
}
HPROF_CLEAR_GC_SCAN_STATE();
if (scanRequired) {
processMarkStack(markContext);
}
}
if (workRequired) {
dvmSignalHeapWorker(false);
}
}
/*
* Sets concurrentStart
*/
void dvmSetTargetHeapConcurrentStart(size_t size)
{
concurrentStart = size;
LOGD_HEAP("dvmSetTargetHeapConcurrentStart %d", size );
}
/*
* Gets TargetHeapMinFree
*/
int dvmGetTargetHeapMinFree()
{
HS_BOILERPLATE();
LOGD_HEAP("dvmGetTargetHeapIdealFree %d", gHs->minFree );
return gHs->minFree;
}
/*
* Sets TargetHeapMinFree
*/
void dvmSetTargetHeapMinFree(size_t size)
{
HS_BOILERPLATE();
gHs->minFree = size;
LOGD_HEAP("dvmSetTargetHeapIdealFree %d", gHs->minFree );
}
