--- a/hotspot/src/share/vm/gc/g1/g1EvacStats.cpp Thu Dec 10 23:02:31 2015 +0000
+++ b/hotspot/src/share/vm/gc/g1/g1EvacStats.cpp Thu Dec 10 14:57:55 2015 +0100
@@ -26,91 +26,97 @@
#include "memory/allocation.inline.hpp"
#include "gc/g1/g1EvacStats.hpp"
#include "gc/shared/gcId.hpp"
+#include "logging/log.hpp"
#include "trace/tracing.hpp"
void G1EvacStats::adjust_desired_plab_sz() {
- if (PrintPLAB) {
- gclog_or_tty->print(" (allocated = " SIZE_FORMAT " wasted = " SIZE_FORMAT " "
+ if (!ResizePLAB) {
+ log_debug(gc, plab)(" (allocated = " SIZE_FORMAT " wasted = " SIZE_FORMAT " "
"unused = " SIZE_FORMAT " used = " SIZE_FORMAT " "
"undo_waste = " SIZE_FORMAT " region_end_waste = " SIZE_FORMAT " "
"regions filled = %u direct_allocated = " SIZE_FORMAT " "
"failure_used = " SIZE_FORMAT " failure_waste = " SIZE_FORMAT ") ",
_allocated, _wasted, _unused, used(), _undo_wasted, _region_end_waste,
_regions_filled, _direct_allocated, _failure_used, _failure_waste);
+ // Clear accumulators for next round.
+ reset();
+ return;
}
- if (ResizePLAB) {
-
- assert(is_object_aligned(max_size()) && min_size() <= max_size(),
- "PLAB clipping computation may be incorrect");
+ assert(is_object_aligned(max_size()) && min_size() <= max_size(),
+ "PLAB clipping computation may be incorrect");
- if (_allocated == 0) {
- assert((_unused == 0),
- "Inconsistency in PLAB stats: "
- "_allocated: " SIZE_FORMAT ", "
- "_wasted: " SIZE_FORMAT ", "
- "_region_end_waste: " SIZE_FORMAT ", "
- "_unused: " SIZE_FORMAT ", "
- "_used : " SIZE_FORMAT,
- _allocated, _wasted, _region_end_waste, _unused, used());
- _allocated = 1;
- }
- // The size of the PLAB caps the amount of space that can be wasted at the
- // end of the collection. In the worst case the last PLAB could be completely
- // empty.
- // This allows us to calculate the new PLAB size to achieve the
- // TargetPLABWastePct given the latest memory usage and that the last buffer
- // will be G1LastPLABAverageOccupancy full.
- //
- // E.g. assume that if in the current GC 100 words were allocated and a
- // TargetPLABWastePct of 10 had been set.
- //
- // So we could waste up to 10 words to meet that percentage. Given that we
- // also assume that that buffer is typically half-full, the new desired PLAB
- // size is set to 20 words.
- //
- // The amount of allocation performed should be independent of the number of
- // threads, so should the maximum waste we can spend in total. So if
- // we used n threads to allocate, each of them can spend maximum waste/n words in
- // a first rough approximation. The number of threads only comes into play later
- // when actually retrieving the actual desired PLAB size.
- //
- // After calculating this optimal PLAB size the algorithm applies the usual
- // exponential decaying average over this value to guess the next PLAB size.
- //
- // We account region end waste fully to PLAB allocation (in the calculation of
- // what we consider as "used_for_waste_calculation" below). This is not
- // completely fair, but is a conservative assumption because PLABs may be sized
- // flexibly while we cannot adjust inline allocations.
- // Allocation during GC will try to minimize region end waste so this impact
- // should be minimal.
- //
- // We need to cover overflow when calculating the amount of space actually used
- // by objects in PLABs when subtracting the region end waste.
- // Region end waste may be higher than actual allocation. This may occur if many
- // threads do not allocate anything but a few rather large objects. In this
- // degenerate case the PLAB size would simply quickly tend to minimum PLAB size,
- // which is an okay reaction.
- size_t const used_for_waste_calculation = used() > _region_end_waste ? used() - _region_end_waste : 0;
+ if (_allocated == 0) {
+ assert((_unused == 0),
+ "Inconsistency in PLAB stats: "
+ "_allocated: " SIZE_FORMAT ", "
+ "_wasted: " SIZE_FORMAT ", "
+ "_region_end_waste: " SIZE_FORMAT ", "
+ "_unused: " SIZE_FORMAT ", "
+ "_used : " SIZE_FORMAT,
+ _allocated, _wasted, _region_end_waste, _unused, used());
+ _allocated = 1;
+ }
+ // The size of the PLAB caps the amount of space that can be wasted at the
+ // end of the collection. In the worst case the last PLAB could be completely
+ // empty.
+ // This allows us to calculate the new PLAB size to achieve the
+ // TargetPLABWastePct given the latest memory usage and that the last buffer
+ // will be G1LastPLABAverageOccupancy full.
+ //
+ // E.g. assume that if in the current GC 100 words were allocated and a
+ // TargetPLABWastePct of 10 had been set.
+ //
+ // So we could waste up to 10 words to meet that percentage. Given that we
+ // also assume that that buffer is typically half-full, the new desired PLAB
+ // size is set to 20 words.
+ //
+ // The amount of allocation performed should be independent of the number of
+ // threads, so should the maximum waste we can spend in total. So if
+ // we used n threads to allocate, each of them can spend maximum waste/n words in
+ // a first rough approximation. The number of threads only comes into play later
+ // when actually retrieving the actual desired PLAB size.
+ //
+ // After calculating this optimal PLAB size the algorithm applies the usual
+ // exponential decaying average over this value to guess the next PLAB size.
+ //
+ // We account region end waste fully to PLAB allocation (in the calculation of
+ // what we consider as "used_for_waste_calculation" below). This is not
+ // completely fair, but is a conservative assumption because PLABs may be sized
+ // flexibly while we cannot adjust inline allocations.
+ // Allocation during GC will try to minimize region end waste so this impact
+ // should be minimal.
+ //
+ // We need to cover overflow when calculating the amount of space actually used
+ // by objects in PLABs when subtracting the region end waste.
+ // Region end waste may be higher than actual allocation. This may occur if many
+ // threads do not allocate anything but a few rather large objects. In this
+ // degenerate case the PLAB size would simply quickly tend to minimum PLAB size,
+ // which is an okay reaction.
+ size_t const used_for_waste_calculation = used() > _region_end_waste ? used() - _region_end_waste : 0;
- size_t const total_waste_allowed = used_for_waste_calculation * TargetPLABWastePct;
- size_t const cur_plab_sz = (size_t)((double)total_waste_allowed / G1LastPLABAverageOccupancy);
- // Take historical weighted average
- _filter.sample(cur_plab_sz);
- // Clip from above and below, and align to object boundary
- size_t plab_sz;
- plab_sz = MAX2(min_size(), (size_t)_filter.average());
- plab_sz = MIN2(max_size(), plab_sz);
- plab_sz = align_object_size(plab_sz);
- // Latch the result
- _desired_net_plab_sz = plab_sz;
- if (PrintPLAB) {
- gclog_or_tty->print(" (plab_sz = " SIZE_FORMAT " desired_plab_sz = " SIZE_FORMAT ") ", cur_plab_sz, plab_sz);
- }
- }
- if (PrintPLAB) {
- gclog_or_tty->cr();
- }
+ size_t const total_waste_allowed = used_for_waste_calculation * TargetPLABWastePct;
+ size_t const cur_plab_sz = (size_t)((double)total_waste_allowed / G1LastPLABAverageOccupancy);
+ // Take historical weighted average
+ _filter.sample(cur_plab_sz);
+ // Clip from above and below, and align to object boundary
+ size_t plab_sz;
+ plab_sz = MAX2(min_size(), (size_t)_filter.average());
+ plab_sz = MIN2(max_size(), plab_sz);
+ plab_sz = align_object_size(plab_sz);
+ // Latch the result
+ _desired_net_plab_sz = plab_sz;
+
+ log_debug(gc, plab)(" (allocated = " SIZE_FORMAT " wasted = " SIZE_FORMAT " "
+ "unused = " SIZE_FORMAT " used = " SIZE_FORMAT " "
+ "undo_waste = " SIZE_FORMAT " region_end_waste = " SIZE_FORMAT " "
+ "regions filled = %u direct_allocated = " SIZE_FORMAT " "
+ "failure_used = " SIZE_FORMAT " failure_waste = " SIZE_FORMAT ") "
+ " (plab_sz = " SIZE_FORMAT " desired_plab_sz = " SIZE_FORMAT ")",
+ _allocated, _wasted, _unused, used(), _undo_wasted, _region_end_waste,
+ _regions_filled, _direct_allocated, _failure_used, _failure_waste,
+ cur_plab_sz, plab_sz);
+
// Clear accumulators for next round.
reset();
}