# HG changeset patch # User tschatzl # Date 1448357752 -3600 # Node ID 3fdfdda0ac1fc1ed83911041b11693dc0d25be7d # Parent f3c9dcc5af96a0bc0f0cd8c36eb20814a8cea34b 8136678: Implement adaptive sizing algorithm for IHOP Summary: Add adaptive sizing for IHOP that maximizes throughput (starts marking as late as possible). This functionality is enabled using a new -XX:+G1AdaptiveIHOP switch (default: false). Reviewed-by: mgerdin, jmasa, pliden diff -r f3c9dcc5af96 -r 3fdfdda0ac1f hotspot/src/share/vm/gc/g1/g1CollectorPolicy.cpp --- a/hotspot/src/share/vm/gc/g1/g1CollectorPolicy.cpp Tue Nov 24 10:22:36 2015 +0100 +++ b/hotspot/src/share/vm/gc/g1/g1CollectorPolicy.cpp Tue Nov 24 10:35:52 2015 +0100 @@ -1239,8 +1239,16 @@ } G1IHOPControl* G1CollectorPolicy::create_ihop_control() const { - return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent, - G1CollectedHeap::heap()->max_capacity()); + if (G1UseAdaptiveIHOP) { + return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, + G1CollectedHeap::heap()->max_capacity(), + &_predictor, + G1ReservePercent, + G1HeapWastePercent); + } else { + return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent, + G1CollectedHeap::heap()->max_capacity()); + } } void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s, diff -r f3c9dcc5af96 -r 3fdfdda0ac1f hotspot/src/share/vm/gc/g1/g1IHOPControl.cpp --- a/hotspot/src/share/vm/gc/g1/g1IHOPControl.cpp Tue Nov 24 10:22:36 2015 +0100 +++ b/hotspot/src/share/vm/gc/g1/g1IHOPControl.cpp Tue Nov 24 10:35:52 2015 +0100 @@ -26,6 +26,7 @@ #include "gc/g1/g1CollectedHeap.inline.hpp" #include "gc/g1/g1ErgoVerbose.hpp" #include "gc/g1/g1IHOPControl.hpp" +#include "gc/g1/g1Predictions.hpp" G1IHOPControl::G1IHOPControl(double initial_ihop_percent, size_t target_occupancy) : _initial_ihop_percent(initial_ihop_percent), @@ -105,6 +106,181 @@ assert(threshold == initial_ihop, "Expected IHOP threshold of " SIZE_FORMAT " but is " SIZE_FORMAT, initial_ihop, threshold); } +#endif + +G1AdaptiveIHOPControl::G1AdaptiveIHOPControl(double ihop_percent, + size_t initial_target_occupancy, + G1Predictions const* predictor, + size_t heap_reserve_percent, + size_t heap_waste_percent) : + G1IHOPControl(ihop_percent, initial_target_occupancy), + _predictor(predictor), + _marking_times_s(10, 0.95), + _allocation_rate_s(10, 0.95), + _last_unrestrained_young_size(0), + _heap_reserve_percent(heap_reserve_percent), + _heap_waste_percent(heap_waste_percent) +{ +} + +size_t G1AdaptiveIHOPControl::actual_target_threshold() const { + // The actual target threshold takes the heap reserve and the expected waste in + // free space into account. + // _heap_reserve is that part of the total heap capacity that is reserved for + // eventual promotion failure. + // _heap_waste is the amount of space will never be reclaimed in any + // heap, so can not be used for allocation during marking and must always be + // considered. + + double safe_total_heap_percentage = MIN2((double)(_heap_reserve_percent + _heap_waste_percent), 100.0); + + return MIN2( + G1CollectedHeap::heap()->max_capacity() * (100.0 - safe_total_heap_percentage) / 100.0, + _target_occupancy * (100.0 - _heap_waste_percent) / 100.0 + ); +} + +bool G1AdaptiveIHOPControl::have_enough_data_for_prediction() const { + return ((size_t)_marking_times_s.num() >= G1AdaptiveIHOPNumInitialSamples) && + ((size_t)_allocation_rate_s.num() >= G1AdaptiveIHOPNumInitialSamples); +} + +size_t G1AdaptiveIHOPControl::get_conc_mark_start_threshold() { + if (have_enough_data_for_prediction()) { + double pred_marking_time = _predictor->get_new_prediction(&_marking_times_s); + double pred_promotion_rate = _predictor->get_new_prediction(&_allocation_rate_s); + + size_t predicted_needed_bytes_during_marking = + (pred_marking_time * pred_promotion_rate + + _last_unrestrained_young_size); // In reality we would need the maximum size of the young gen during marking. This is a conservative estimate. + + size_t internal_threshold = actual_target_threshold(); + size_t predicted_initiating_threshold = predicted_needed_bytes_during_marking < internal_threshold ? + internal_threshold - predicted_needed_bytes_during_marking : + 0; + return predicted_initiating_threshold; + } else { + // Use the initial value. + return _initial_ihop_percent * _target_occupancy / 100.0; + } +} + +void G1AdaptiveIHOPControl::update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size) { + assert(allocation_time_s >= 0.0, "Allocation time must be positive but is %.3f", allocation_time_s); + double allocation_rate = (double) allocated_bytes / allocation_time_s; + _allocation_rate_s.add(allocation_rate); + + _last_allocation_bytes = allocated_bytes; + _last_unrestrained_young_size = additional_buffer_size; +} + +void G1AdaptiveIHOPControl::update_marking_length(double marking_length_s) { + assert(marking_length_s >= 0.0, "Marking length must be larger than zero but is %.3f", marking_length_s); + _marking_times_s.add(marking_length_s); +} + +void G1AdaptiveIHOPControl::print() { + ergo_verbose6(ErgoIHOP, + "basic information", + ergo_format_reason("value update") + ergo_format_byte_perc("threshold") + ergo_format_byte("target occupancy") + ergo_format_byte("current occupancy") + ergo_format_double("recent old gen allocation rate") + ergo_format_double("recent marking phase length"), + get_conc_mark_start_threshold(), + percent_of(get_conc_mark_start_threshold(), _target_occupancy), + _target_occupancy, + G1CollectedHeap::heap()->used(), + _allocation_rate_s.last(), + _marking_times_s.last() + ); + size_t actual_target = actual_target_threshold(); + ergo_verbose6(ErgoIHOP, + "adaptive IHOP information", + ergo_format_reason("value update") + ergo_format_byte_perc("threshold") + ergo_format_byte("internal target occupancy") + ergo_format_double("predicted old gen allocation rate") + ergo_format_double("predicted marking phase length") + ergo_format_str("prediction active"), + get_conc_mark_start_threshold(), + percent_of(get_conc_mark_start_threshold(), actual_target), + actual_target, + _predictor->get_new_prediction(&_allocation_rate_s), + _predictor->get_new_prediction(&_marking_times_s), + have_enough_data_for_prediction() ? "true" : "false" + ); +} + +#ifndef PRODUCT +void G1AdaptiveIHOPControl::test() { + size_t const initial_threshold = 45; + size_t const young_size = 10; + size_t const target_size = 100; + + // The final IHOP value is always + // target_size - (young_size + alloc_amount/alloc_time * marking_time) + + G1Predictions pred(0.95); + G1AdaptiveIHOPControl ctrl(initial_threshold, target_size, &pred, 0, 0); + + // First "load". + size_t const alloc_time1 = 2; + size_t const alloc_amount1 = 10; + size_t const marking_time1 = 2; + size_t const settled_ihop1 = target_size - (young_size + alloc_amount1/alloc_time1 * marking_time1); + + size_t threshold; + threshold = ctrl.get_conc_mark_start_threshold(); + assert(threshold == initial_threshold, + "Expected IHOP threshold of " SIZE_FORMAT " but is " SIZE_FORMAT, initial_threshold, threshold); + for (size_t i = 0; i < G1AdaptiveIHOPNumInitialSamples - 1; i++) { + ctrl.update_allocation_info(alloc_time1, alloc_amount1, young_size); + ctrl.update_marking_length(marking_time1); + // Not enough data yet. + threshold = ctrl.get_conc_mark_start_threshold(); + assert(threshold == initial_threshold, + "Expected IHOP threshold of " SIZE_FORMAT " but is " SIZE_FORMAT, initial_threshold, threshold); + } + + test_update(&ctrl, alloc_time1, alloc_amount1, young_size, marking_time1); + + threshold = ctrl.get_conc_mark_start_threshold(); + assert(threshold == settled_ihop1, + "Expected IHOP threshold to settle at " SIZE_FORMAT " but is " SIZE_FORMAT, settled_ihop1, threshold); + + // Second "load". A bit higher allocation rate. + size_t const alloc_time2 = 2; + size_t const alloc_amount2 = 30; + size_t const marking_time2 = 2; + size_t const settled_ihop2 = target_size - (young_size + alloc_amount2/alloc_time2 * marking_time2); + + test_update(&ctrl, alloc_time2, alloc_amount2, young_size, marking_time2); + + threshold = ctrl.get_conc_mark_start_threshold(); + assert(threshold < settled_ihop1, + "Expected IHOP threshold to settle at a value lower than " SIZE_FORMAT " but is " SIZE_FORMAT, settled_ihop1, threshold); + + // Third "load". Very high (impossible) allocation rate. + size_t const alloc_time3 = 1; + size_t const alloc_amount3 = 50; + size_t const marking_time3 = 2; + size_t const settled_ihop3 = 0; + + test_update(&ctrl, alloc_time3, alloc_amount3, young_size, marking_time3); + threshold = ctrl.get_conc_mark_start_threshold(); + + assert(threshold == settled_ihop3, + "Expected IHOP threshold to settle at " SIZE_FORMAT " but is " SIZE_FORMAT, settled_ihop3, threshold); + + // And back to some arbitrary value. + test_update(&ctrl, alloc_time2, alloc_amount2, young_size, marking_time2); + + threshold = ctrl.get_conc_mark_start_threshold(); + assert(threshold > settled_ihop3, + "Expected IHOP threshold to settle at value larger than " SIZE_FORMAT " but is " SIZE_FORMAT, settled_ihop3, threshold); +} void IHOP_test() { G1StaticIHOPControl::test(); diff -r f3c9dcc5af96 -r 3fdfdda0ac1f hotspot/src/share/vm/gc/g1/g1IHOPControl.hpp --- a/hotspot/src/share/vm/gc/g1/g1IHOPControl.hpp Tue Nov 24 10:22:36 2015 +0100 +++ b/hotspot/src/share/vm/gc/g1/g1IHOPControl.hpp Tue Nov 24 10:35:52 2015 +0100 @@ -26,6 +26,9 @@ #define SHARE_VM_GC_G1_G1IHOPCONTROL_HPP #include "memory/allocation.hpp" +#include "utilities/numberSeq.hpp" + +class G1Predictions; // Base class for algorithms that calculate the heap occupancy at which // concurrent marking should start. This heap usage threshold should be relative @@ -95,4 +98,53 @@ #endif }; +// This algorithm tries to return a concurrent mark starting occupancy value that +// makes sure that during marking the given target occupancy is never exceeded, +// based on predictions of current allocation rate and time periods between +// initial mark and the first mixed gc. +class G1AdaptiveIHOPControl : public G1IHOPControl { + size_t _heap_reserve_percent; // Percentage of maximum heap capacity we should avoid to touch + size_t _heap_waste_percent; // Percentage of free heap that should be considered as waste. + + const G1Predictions * _predictor; + + TruncatedSeq _marking_times_s; + TruncatedSeq _allocation_rate_s; + + size_t _last_allocation_bytes; // Most recent mutator allocation since last GC. + // The most recent unrestrained size of the young gen. This is used as an additional + // factor in the calculation of the threshold, as the threshold is based on + // non-young gen occupancy at the end of GC. For the IHOP threshold, we need to + // consider the young gen size during that time too. + // Since we cannot know what young gen sizes are used in the future, we will just + // use the current one. We expect that this one will be one with a fairly large size, + // as there is no marking or mixed gc that could impact its size too much. + size_t _last_unrestrained_young_size; + + bool have_enough_data_for_prediction() const; + + // The "actual" target threshold the algorithm wants to keep during and at the + // end of marking. This is typically lower than the requested threshold, as the + // algorithm needs to consider restrictions by the environment. + size_t actual_target_threshold() const; + protected: + virtual double last_marking_length_s() const { return _marking_times_s.last(); } + public: + G1AdaptiveIHOPControl(double ihop_percent, + size_t initial_target_occupancy, + G1Predictions const* predictor, + size_t heap_reserve_percent, // The percentage of total heap capacity that should not be tapped into. + size_t heap_waste_percent); // The percentage of the free space in the heap that we think is not usable for allocation. + + virtual size_t get_conc_mark_start_threshold(); + + virtual void update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size); + virtual void update_marking_length(double marking_length_s); + + virtual void print(); +#ifndef PRODUCT + static void test(); +#endif +}; + #endif // SHARE_VM_GC_G1_G1IHOPCONTROL_HPP diff -r f3c9dcc5af96 -r 3fdfdda0ac1f hotspot/src/share/vm/gc/g1/g1RemSetSummary.cpp --- a/hotspot/src/share/vm/gc/g1/g1RemSetSummary.cpp Tue Nov 24 10:22:36 2015 +0100 +++ b/hotspot/src/share/vm/gc/g1/g1RemSetSummary.cpp Tue Nov 24 10:35:52 2015 +0100 @@ -125,14 +125,6 @@ _sampling_thread_vtime = other->sampling_thread_vtime() - _sampling_thread_vtime; } -static double percent_of(size_t numerator, size_t denominator) { - if (denominator != 0) { - return (double)numerator / denominator * 100.0f; - } else { - return 0.0f; - } -} - static size_t round_to_K(size_t value) { return value / K; } diff -r f3c9dcc5af96 -r 3fdfdda0ac1f hotspot/src/share/vm/gc/g1/g1_globals.hpp --- a/hotspot/src/share/vm/gc/g1/g1_globals.hpp Tue Nov 24 10:22:36 2015 +0100 +++ b/hotspot/src/share/vm/gc/g1/g1_globals.hpp Tue Nov 24 10:35:52 2015 +0100 @@ -33,6 +33,16 @@ #define G1_FLAGS(develop, develop_pd, product, product_pd, diagnostic, experimental, notproduct, manageable, product_rw, range, constraint) \ \ + product(bool, G1UseAdaptiveIHOP, false, \ + "Adaptively adjust InitiatingHeapOccupancyPercent from the " \ + "initial value.") \ + \ + experimental(size_t, G1AdaptiveIHOPNumInitialSamples, 3, \ + "How many completed time periods from initial mark to first " \ + "mixed gc are required to use the input values for prediction " \ + "of the optimal occupancy to start marking.") \ + range(1, max_intx) \ + \ product(uintx, G1ConfidencePercent, 50, \ "Confidence level for MMU/pause predictions") \ range(0, 100) \ diff -r f3c9dcc5af96 -r 3fdfdda0ac1f hotspot/src/share/vm/utilities/globalDefinitions.hpp --- a/hotspot/src/share/vm/utilities/globalDefinitions.hpp Tue Nov 24 10:22:36 2015 +0100 +++ b/hotspot/src/share/vm/utilities/globalDefinitions.hpp Tue Nov 24 10:35:52 2015 +0100 @@ -565,6 +565,13 @@ return fabs(value); } +// Returns numerator/denominator as percentage value from 0 to 100. If denominator +// is zero, return 0.0. +template +inline double percent_of(T numerator, T denominator) { + return denominator != 0 ? (double)numerator / denominator * 100.0 : 0.0; +} + //---------------------------------------------------------------------------------------------------- // Special casts // Cast floats into same-size integers and vice-versa w/o changing bit-pattern