/*
* Sets the maximum number of bytes that the heap source is allowed
* to allocate from the system. Clamps to the appropriate maximum
* value.
*/
static void setIdealFootprint(size_t max)
{
HS_BOILERPLATE();
HeapSource *hs = gHs;
size_t maximumSize = getMaximumSize(hs);
if (max > maximumSize) {
LOGI_HEAP("Clamp target GC heap from %zd.%03zdMB to %u.%03uMB",
FRACTIONAL_MB(max),
FRACTIONAL_MB(maximumSize));
max = maximumSize;
}
/* Convert max into a size that applies to the active heap.
* Old heaps will count against the ideal size.
*/
size_t overhead = getSoftFootprint(false);
size_t activeMax;
if (overhead < max) {
activeMax = max - overhead;
} else {
activeMax = 0;
}
setSoftLimit(hs, activeMax);
hs->idealSize = max;
}
/*
* Allocates <n> bytes of zeroed data.
*/
void* dvmHeapSourceAlloc(size_t n)
{
HS_BOILERPLATE();
HeapSource *hs = gHs;
Heap* heap = hs2heap(hs);
if (heap->bytesAllocated + n > hs->softLimit) {
/*
* This allocation would push us over the soft limit; act as
* if the heap is full.
*/
LOGV_HEAP("softLimit of %zd.%03zdMB hit for %zd-byte allocation",
FRACTIONAL_MB(hs->softLimit), n);
return NULL;
}
void* ptr = mspace_calloc(heap->msp, 1, n);
if (ptr == NULL) {
return NULL;
}
countAllocation(heap, ptr);
/*
* Check to see if a concurrent GC should be initiated.
*/
if (gDvm.gcHeap->gcRunning || !hs->hasGcThread) {
/*
* The garbage collector thread is already running or has yet
* to be started. Do nothing.
*/
return ptr;
}
if (heap->bytesAllocated > heap->concurrentStartBytes) {
/*
* We have exceeded the allocation threshold. Wake up the
* garbage collector.
*/
dvmSignalCond(&gHs->gcThreadCond);
}
return ptr;
}
/*
* Allocates <n> bytes of zeroed data.
*/
void* dvmHeapSourceAlloc(size_t n)
{
HS_BOILERPLATE();
HeapSource *hs = gHs;
Heap* heap = hs2heap(hs);
if (heap->bytesAllocated + n > hs->softLimit) {
/*
* This allocation would push us over the soft limit; act as
* if the heap is full.
*/
LOGV_HEAP("softLimit of %zd.%03zdMB hit for %zd-byte allocation",
FRACTIONAL_MB(hs->softLimit), n);
return NULL;
}
void* ptr;
if (gDvm.lowMemoryMode) {
/* This is only necessary because mspace_calloc always memsets the
* allocated memory to 0. This is bad for memory usage since it leads
* to dirty zero pages. If low memory mode is enabled, we use
* mspace_malloc which doesn't memset the allocated memory and madvise
* the page aligned region back to the kernel.
*/
ptr = mspace_malloc(heap->msp, n);
if (ptr == NULL) {
return NULL;
}
uintptr_t zero_begin = (uintptr_t)ptr;
uintptr_t zero_end = (uintptr_t)ptr + n;
/* Calculate the page aligned region.
*/
uintptr_t begin = ALIGN_UP_TO_PAGE_SIZE(zero_begin);
uintptr_t end = zero_end & ~(uintptr_t)(SYSTEM_PAGE_SIZE - 1);
/* If our allocation spans more than one page, we attempt to madvise.
*/
if (begin < end) {
/* madvise the page aligned region to kernel.
*/
madvise((void*)begin, end - begin, MADV_DONTNEED);
/* Zero the region after the page aligned region.
*/
memset((void*)end, 0, zero_end - end);
/* Zero out the region before the page aligned region.
*/
zero_end = begin;
}
memset((void*)zero_begin, 0, zero_end - zero_begin);
} else {
ptr = mspace_calloc(heap->msp, 1, n);
if (ptr == NULL) {
return NULL;
}
}
countAllocation(heap, ptr);
/*
* Check to see if a concurrent GC should be initiated.
*/
if (gDvm.gcHeap->gcRunning || !hs->hasGcThread) {
/*
* The garbage collector thread is already running or has yet
* to be started. Do nothing.
*/
return ptr;
}
if (heap->bytesAllocated > heap->concurrentStartBytes) {
/*
* We have exceeded the allocation threshold. Wake up the
* garbage collector.
*/
dvmSignalCond(&gHs->gcThreadCond);
}
return ptr;
}
/* Try as hard as possible to allocate some memory.
*/
static void *tryMalloc(size_t size)
{
void *ptr;
/* Don't try too hard if there's no way the allocation is
* going to succeed. We have to collect SoftReferences before
* throwing an OOME, though.
*/
if (size >= gDvm.heapGrowthLimit) {
ALOGW("%zd byte allocation exceeds the %zd byte maximum heap size",
size, gDvm.heapGrowthLimit);
ptr = NULL;
goto collect_soft_refs;
}
//TODO: figure out better heuristics
// There will be a lot of churn if someone allocates a bunch of
// big objects in a row, and we hit the frag case each time.
// A full GC for each.
// Maybe we grow the heap in bigger leaps
// Maybe we skip the GC if the size is large and we did one recently
// (number of allocations ago) (watch for thread effects)
// DeflateTest allocs a bunch of ~128k buffers w/in 0-5 allocs of each other
// (or, at least, there are only 0-5 objects swept each time)
ptr = dvmHeapSourceAlloc(size);
if (ptr != NULL) {
return ptr;
}
/*
* The allocation failed. If the GC is running, block until it
* completes and retry.
*/
if (gDvm.gcHeap->gcRunning) {
/*
* The GC is concurrently tracing the heap. Release the heap
* lock, wait for the GC to complete, and retrying allocating.
*/
dvmWaitForConcurrentGcToComplete();
ptr = dvmHeapSourceAlloc(size);
if (ptr != NULL) {
return ptr;
}
}
/*
* Another failure. Our thread was starved or there may be too
* many live objects. Try a foreground GC. This will have no
* effect if the concurrent GC is already running.
*/
gcForMalloc(false);
ptr = dvmHeapSourceAlloc(size);
if (ptr != NULL) {
return ptr;
}
/* Even that didn't work; this is an exceptional state.
* Try harder, growing the heap if necessary.
*/
ptr = dvmHeapSourceAllocAndGrow(size);
if (ptr != NULL) {
size_t newHeapSize;
newHeapSize = dvmHeapSourceGetIdealFootprint();
//TODO: may want to grow a little bit more so that the amount of free
// space is equal to the old free space + the utilization slop for
// the new allocation.
LOGI_HEAP("Grow heap (frag case) to "
"%zu.%03zuMB for %zu-byte allocation",
FRACTIONAL_MB(newHeapSize), size);
return ptr;
}
/* Most allocations should have succeeded by now, so the heap
* is really full, really fragmented, or the requested size is
* really big. Do another GC, collecting SoftReferences this
* time. The VM spec requires that all SoftReferences have
* been collected and cleared before throwing an OOME.
*/
//TODO: wait for the finalizers from the previous GC to finish
collect_soft_refs:
LOGI_HEAP("Forcing collection of SoftReferences for %zu-byte allocation",
size);
gcForMalloc(true);
ptr = dvmHeapSourceAllocAndGrow(size);
if (ptr != NULL) {
return ptr;
}
//TODO: maybe wait for finalizers and try one last time
LOGE_HEAP("Out of memory on a %zd-byte allocation.", size);
//TODO: tell the HeapSource to dump its state
dvmDumpThread(dvmThreadSelf(), false);
return NULL;
}
