< prev index next > src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp
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*
*/
#include "precompiled.hpp"
#include "gc/shared/tlab_globals.hpp"
+ #include "gc/shenandoah/shenandoahBarrierSet.hpp"
#include "gc/shenandoah/shenandoahFreeSet.hpp"
#include "gc/shenandoah/shenandoahHeap.inline.hpp"
#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
+ #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
+ #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
#include "logging/logStream.hpp"
#include "memory/resourceArea.hpp"
#include "runtime/orderAccess.hpp"
ShenandoahFreeSet::ShenandoahFreeSet(ShenandoahHeap* heap, size_t max_regions) :
assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT " (left: " SIZE_FORMAT ", right: " SIZE_FORMAT ")",
idx, _max, _collector_leftmost, _collector_rightmost);
return _collector_free_bitmap.at(idx);
}
+ HeapWord* ShenandoahFreeSet::allocate_with_affiliation(ShenandoahRegionAffiliation affiliation, ShenandoahAllocRequest& req, bool& in_new_region) {
+ for (size_t c = _collector_rightmost + 1; c > _collector_leftmost; c--) {
+ // size_t is unsigned, need to dodge underflow when _leftmost = 0
+ size_t idx = c - 1;
+ if (is_collector_free(idx)) {
+ ShenandoahHeapRegion* r = _heap->get_region(idx);
+ if (r->affiliation() == affiliation) {
+ HeapWord* result = try_allocate_in(r, req, in_new_region);
+ if (result != NULL) {
+ return result;
+ }
+ }
+ }
+ }
+ return NULL;
+ }
+
HeapWord* ShenandoahFreeSet::allocate_single(ShenandoahAllocRequest& req, bool& in_new_region) {
// Scan the bitmap looking for a first fit.
//
// Leftmost and rightmost bounds provide enough caching to walk bitmap efficiently. Normally,
// we would find the region to allocate at right away.
// There is no recovery. Mutator does not touch collector view at all.
break;
}
case ShenandoahAllocRequest::_alloc_gclab:
case ShenandoahAllocRequest::_alloc_shared_gc: {
! // size_t is unsigned, need to dodge underflow when _leftmost = 0
!
! // Fast-path: try to allocate in the collector view first
! for (size_t c = _collector_rightmost + 1; c > _collector_leftmost; c--) {
! size_t idx = c - 1;
! if (is_collector_free(idx)) {
! HeapWord* result = try_allocate_in(_heap->get_region(idx), req, in_new_region);
! if (result != NULL) {
! return result;
- }
- }
}
// No dice. Can we borrow space from mutator view?
if (!ShenandoahEvacReserveOverflow) {
return NULL;
}
! // Try to steal the empty region from the mutator view
for (size_t c = _mutator_rightmost + 1; c > _mutator_leftmost; c--) {
size_t idx = c - 1;
if (is_mutator_free(idx)) {
ShenandoahHeapRegion* r = _heap->get_region(idx);
if (can_allocate_from(r)) {
// There is no recovery. Mutator does not touch collector view at all.
break;
}
case ShenandoahAllocRequest::_alloc_gclab:
+ case ShenandoahAllocRequest::_alloc_plab:
case ShenandoahAllocRequest::_alloc_shared_gc: {
! // First try to fit into a region that is already in use in the same generation.
! HeapWord* result = allocate_with_affiliation(req.affiliation(), req, in_new_region);
! if (result != NULL) {
! return result;
! }
! // Then try a free region that is dedicated to GC allocations.
! result = allocate_with_affiliation(FREE, req, in_new_region);
! if (result != NULL) {
! return result;
}
// No dice. Can we borrow space from mutator view?
if (!ShenandoahEvacReserveOverflow) {
return NULL;
}
! // Try to steal an empty region from the mutator view.
for (size_t c = _mutator_rightmost + 1; c > _mutator_leftmost; c--) {
size_t idx = c - 1;
if (is_mutator_free(idx)) {
ShenandoahHeapRegion* r = _heap->get_region(idx);
if (can_allocate_from(r)) {
}
// No dice. Do not try to mix mutator and GC allocations, because
// URWM moves due to GC allocations would expose unparsable mutator
// allocations.
-
break;
}
default:
ShouldNotReachHere();
}
-
return NULL;
}
HeapWord* ShenandoahFreeSet::try_allocate_in(ShenandoahHeapRegion* r, ShenandoahAllocRequest& req, bool& in_new_region) {
assert (!has_no_alloc_capacity(r), "Performance: should avoid full regions on this path: " SIZE_FORMAT, r->index());
return NULL;
}
try_recycle_trashed(r);
in_new_region = r->is_empty();
HeapWord* result = NULL;
size_t size = req.size();
if (ShenandoahElasticTLAB && req.is_lab_alloc()) {
! size_t free = align_down(r->free() >> LogHeapWordSize, MinObjAlignment);
! if (size > free) {
! size = free;
}
! if (size >= req.min_size()) {
! result = r->allocate(size, req.type());
! assert (result != NULL, "Allocation must succeed: free " SIZE_FORMAT ", actual " SIZE_FORMAT, free, size);
}
} else {
! result = r->allocate(size, req.type());
}
if (result != NULL) {
// Allocation successful, bump stats:
if (req.is_mutator_alloc()) {
increase_used(size * HeapWordSize);
}
! // Record actual allocation size
! req.set_actual_size(size);
!
! if (req.is_gc_alloc()) {
- r->set_update_watermark(r->top());
}
}
if (result == NULL || has_no_alloc_capacity(r)) {
// Region cannot afford this or future allocations. Retire it.
return NULL;
}
try_recycle_trashed(r);
+ if (r->affiliation() == ShenandoahRegionAffiliation::FREE) {
+ ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
+
+ r->set_affiliation(req.affiliation());
+ r->set_update_watermark(r->bottom());
+
+ // Any OLD region allocated during concurrent coalesce-and-fill does not need to be coalesced and filled because
+ // all objects allocated within this region are above TAMS (and thus are implicitly marked). In case this is an
+ // OLD region and concurrent preparation for mixed evacuations visits this region before the start of the next
+ // old-gen concurrent mark (i.e. this region is allocated following the start of old-gen concurrent mark but before
+ // concurrent preparations for mixed evacuations are completed), we mark this region as not requiring any
+ // coalesce-and-fill processing. This code is only necessary if req.affiliation() is OLD, but harmless if not.
+ r->end_preemptible_coalesce_and_fill();
+ ctx->capture_top_at_mark_start(r);
+
+ assert(ctx->top_at_mark_start(r) == r->bottom(), "Newly established allocation region starts with TAMS equal to bottom");
+ assert(ctx->is_bitmap_clear_range(ctx->top_bitmap(r), r->end()), "Bitmap above top_bitmap() must be clear");
+
+ // Leave top_bitmap alone. The first time a heap region is put into service, top_bitmap should equal end.
+ // Thereafter, it should represent the upper bound on parts of the bitmap that need to be cleared.
+ log_debug(gc)("NOT clearing bitmap for region " SIZE_FORMAT ", top_bitmap: "
+ PTR_FORMAT " at transition from FREE to %s",
+ r->index(), p2i(ctx->top_bitmap(r)), affiliation_name(req.affiliation()));
+ } else if (r->affiliation() != req.affiliation()) {
+ return NULL;
+ }
+
in_new_region = r->is_empty();
HeapWord* result = NULL;
size_t size = req.size();
+ // req.size() is in words, free() is in bytes.
if (ShenandoahElasticTLAB && req.is_lab_alloc()) {
! if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
! // Need to assure that plabs are aligned on multiple of card region.
! size_t free = r->free();
+ size_t usable_free = (free / CardTable::card_size) << CardTable::card_shift;
+ free /= HeapWordSize;
+ usable_free /= HeapWordSize;
+ if (size > usable_free) {
+ size = usable_free;
+ }
+ if (size >= req.min_size()) {
+ result = r->allocate_aligned(size, req, CardTable::card_size);
+ if (result != nullptr && free > usable_free) {
+ // Account for the alignment padding
+ size_t padding = (free - usable_free) * HeapWordSize;
+ increase_used(padding);
+ assert(r->affiliation() == ShenandoahRegionAffiliation::OLD_GENERATION, "All PLABs reside in old-gen");
+ _heap->old_generation()->increase_used(padding);
+ // For verification consistency, we need to report this padding to _heap
+ _heap->increase_used(padding);
+ }
+ }
+ } else {
+ size_t free = align_down(r->free() >> LogHeapWordSize, MinObjAlignment);
+ if (size > free) {
+ size = free;
+ }
+ if (size >= req.min_size()) {
+ result = r->allocate(size, req);
+ assert (result != NULL, "Allocation must succeed: free " SIZE_FORMAT ", actual " SIZE_FORMAT, free, size);
+ }
}
! } else if (req.is_lab_alloc() && req.type() == ShenandoahAllocRequest::_alloc_plab) {
! size_t free = r->free();
! size_t usable_free = (free / CardTable::card_size) << CardTable::card_shift;
+ free /= HeapWordSize;
+ usable_free /= HeapWordSize;
+ if (size <= usable_free) {
+ assert(size % CardTable::card_size_in_words == 0, "PLAB size must be multiple of remembered set card size");
+
+ result = r->allocate_aligned(size, req, CardTable::card_size);
+ if (result != nullptr) {
+ // Account for the alignment padding
+ size_t padding = (free - usable_free) * HeapWordSize;
+ increase_used(padding);
+ assert(r->affiliation() == ShenandoahRegionAffiliation::OLD_GENERATION, "All PLABs reside in old-gen");
+ _heap->old_generation()->increase_used(padding);
+ // For verification consistency, we need to report this padding to _heap
+ _heap->increase_used(padding);
+ }
}
} else {
! result = r->allocate(size, req);
}
if (result != NULL) {
+ // Record actual allocation size
+ req.set_actual_size(size);
+
// Allocation successful, bump stats:
if (req.is_mutator_alloc()) {
increase_used(size * HeapWordSize);
+ } else if (req.is_gc_alloc()) {
+ // For GC allocations, we advance update_watermark because the objects relocated into this memory during
+ // evacuation are not updated during evacuation. For both young and old regions r, it is essential that all
+ // PLABs be made parsable at the end of evacuation. This is enabled by retiring all plabs at end of evacuation.
+ // TODO: Making a PLAB parsable involves placing a filler object in its remnant memory but does not require
+ // that the PLAB be disabled for all future purposes. We may want to introduce a new service to make the
+ // PLABs parsable while still allowing the PLAB to serve future allocation requests that arise during the
+ // next evacuation pass.
+ r->set_update_watermark(r->top());
}
! if (r->affiliation() == ShenandoahRegionAffiliation::YOUNG_GENERATION) {
! _heap->young_generation()->increase_used(size * HeapWordSize);
! } else if (r->affiliation() == ShenandoahRegionAffiliation::OLD_GENERATION) {
! _heap->old_generation()->increase_used(size * HeapWordSize);
}
}
if (result == NULL || has_no_alloc_capacity(r)) {
// Region cannot afford this or future allocations. Retire it.
// Record the remainder as allocation waste
if (req.is_mutator_alloc()) {
size_t waste = r->free();
if (waste > 0) {
increase_used(waste);
+ _heap->generation_for(req.affiliation())->increase_allocated(waste);
_heap->notify_mutator_alloc_words(waste >> LogHeapWordSize, true);
}
}
size_t num = r->index();
end++;
};
size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
+ ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
// Initialize regions:
for (size_t i = beg; i <= end; i++) {
ShenandoahHeapRegion* r = _heap->get_region(i);
try_recycle_trashed(r);
used_words = remainder;
} else {
used_words = ShenandoahHeapRegion::region_size_words();
}
! r->set_top(r->bottom() + used_words);
_mutator_free_bitmap.clear_bit(r->index());
}
// While individual regions report their true use, all humongous regions are
// marked used in the free set.
increase_used(ShenandoahHeapRegion::region_size_bytes() * num);
if (remainder != 0) {
// Record this remainder as allocation waste
! _heap->notify_mutator_alloc_words(ShenandoahHeapRegion::region_size_words() - remainder, true);
}
// Allocated at left/rightmost? Move the bounds appropriately.
if (beg == _mutator_leftmost || end == _mutator_rightmost) {
adjust_bounds();
used_words = remainder;
} else {
used_words = ShenandoahHeapRegion::region_size_words();
}
! r->set_affiliation(req.affiliation());
+ r->set_update_watermark(r->bottom());
+ r->set_top(r->bottom()); // Set top to bottom so we can capture TAMS
+ ctx->capture_top_at_mark_start(r);
+ r->set_top(r->bottom() + used_words); // Then change top to reflect allocation of humongous object.
+ assert(ctx->top_at_mark_start(r) == r->bottom(), "Newly established allocation region starts with TAMS equal to bottom");
+ assert(ctx->is_bitmap_clear_range(ctx->top_bitmap(r), r->end()), "Bitmap above top_bitmap() must be clear");
+
+ // Leave top_bitmap alone. The first time a heap region is put into service, top_bitmap should equal end.
+ // Thereafter, it should represent the upper bound on parts of the bitmap that need to be cleared.
+ // ctx->clear_bitmap(r);
+ log_debug(gc)("NOT clearing bitmap for Humongous region [" PTR_FORMAT ", " PTR_FORMAT "], top_bitmap: "
+ PTR_FORMAT " at transition from FREE to %s",
+ p2i(r->bottom()), p2i(r->end()), p2i(ctx->top_bitmap(r)), affiliation_name(req.affiliation()));
_mutator_free_bitmap.clear_bit(r->index());
}
// While individual regions report their true use, all humongous regions are
// marked used in the free set.
increase_used(ShenandoahHeapRegion::region_size_bytes() * num);
+ if (req.affiliation() == ShenandoahRegionAffiliation::YOUNG_GENERATION) {
+ _heap->young_generation()->increase_used(words_size * HeapWordSize);
+ } else if (req.affiliation() == ShenandoahRegionAffiliation::OLD_GENERATION) {
+ _heap->old_generation()->increase_used(words_size * HeapWordSize);
+ }
+
if (remainder != 0) {
// Record this remainder as allocation waste
! size_t waste = ShenandoahHeapRegion::region_size_words() - remainder;
+ _heap->notify_mutator_alloc_words(waste, true);
+ _heap->generation_for(req.affiliation())->increase_allocated(waste * HeapWordSize);
}
// Allocated at left/rightmost? Move the bounds appropriately.
if (beg == _mutator_leftmost || end == _mutator_rightmost) {
adjust_bounds();
if (touches_bounds(idx)) {
adjust_bounds();
}
assert_bounds();
+
+ // We do not ensure that the region is no longer trash,
+ // relying on try_allocate_in(), which always comes next,
+ // to recycle trash before attempting to allocate anything in the region.
}
void ShenandoahFreeSet::clear() {
shenandoah_assert_heaplocked();
clear_internal();
void ShenandoahFreeSet::rebuild() {
shenandoah_assert_heaplocked();
clear();
+ log_debug(gc)("Rebuilding FreeSet");
for (size_t idx = 0; idx < _heap->num_regions(); idx++) {
ShenandoahHeapRegion* region = _heap->get_region(idx);
if (region->is_alloc_allowed() || region->is_trash()) {
assert(!region->is_cset(), "Shouldn't be adding those to the free set");
_capacity += alloc_capacity(region);
assert(_used <= _capacity, "must not use more than we have");
assert(!is_mutator_free(idx), "We are about to add it, it shouldn't be there already");
_mutator_free_bitmap.set_bit(idx);
+
+ log_debug(gc)(" Setting Region " SIZE_FORMAT " _mutator_free_bitmap bit to true", idx);
}
}
// Evac reserve: reserve trailing space for evacuations
size_t to_reserve = _heap->max_capacity() / 100 * ShenandoahEvacReserve;
_mutator_free_bitmap.clear_bit(idx);
_collector_free_bitmap.set_bit(idx);
size_t ac = alloc_capacity(region);
_capacity -= ac;
reserved += ac;
+ log_debug(gc)(" Shifting region " SIZE_FORMAT " from mutator_free to collector_free", idx);
}
}
recompute_bounds();
assert_bounds();
switch (req.type()) {
case ShenandoahAllocRequest::_alloc_shared:
case ShenandoahAllocRequest::_alloc_shared_gc:
in_new_region = true;
return allocate_contiguous(req);
+ case ShenandoahAllocRequest::_alloc_plab:
case ShenandoahAllocRequest::_alloc_gclab:
case ShenandoahAllocRequest::_alloc_tlab:
in_new_region = false;
assert(false, "Trying to allocate TLAB larger than the humongous threshold: " SIZE_FORMAT " > " SIZE_FORMAT,
req.size(), ShenandoahHeapRegion::humongous_threshold_words());
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