src/hotspot/share/gc/shenandoah/heuristics/shenandoahHeuristics.cpp - platform/libcore - Git at Google

 /*
  * Copyright (c) 2018, 2020, Red Hat, Inc. All rights reserved.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */

 #include "precompiled.hpp"

 #include "gc/shared/gcCause.hpp"
 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
 #include "logging/log.hpp"
 #include "logging/logTag.hpp"

 int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) {
   if (a._garbage > b._garbage)
     return -1;
   else if (a._garbage < b._garbage)
     return 1;
   else return 0;
 }

 ShenandoahHeuristics::ShenandoahHeuristics() :
   _region_data(NULL),
   _degenerated_cycles_in_a_row(0),
   _successful_cycles_in_a_row(0),
   _cycle_start(os::elapsedTime()),
   _last_cycle_end(0),
   _gc_times_learned(0),
   _gc_time_penalties(0),
   _gc_time_history(new TruncatedSeq(5)),
   _metaspace_oom()
 {
   // No unloading during concurrent mark? Communicate that to heuristics
   if (!ClassUnloadingWithConcurrentMark) {
     FLAG_SET_DEFAULT(ShenandoahUnloadClassesFrequency, 0);
   }

   size_t num_regions = ShenandoahHeap::heap()->num_regions();
   assert(num_regions > 0, "Sanity");

   _region_data = NEW_C_HEAP_ARRAY(RegionData, num_regions, mtGC);
 }

 ShenandoahHeuristics::~ShenandoahHeuristics() {
   FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
 }

 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
   assert(collection_set->count() == 0, "Must be empty");

   ShenandoahHeap* heap = ShenandoahHeap::heap();

   // Check all pinned regions have updated status before choosing the collection set.
   heap->assert_pinned_region_status();

   // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.

   size_t num_regions = heap->num_regions();

   RegionData* candidates = _region_data;

   size_t cand_idx = 0;

   size_t total_garbage = 0;

   size_t immediate_garbage = 0;
   size_t immediate_regions = 0;

   size_t free = 0;
   size_t free_regions = 0;

   ShenandoahMarkingContext* const ctx = heap->complete_marking_context();

   for (size_t i = 0; i < num_regions; i++) {
     ShenandoahHeapRegion* region = heap->get_region(i);

     size_t garbage = region->garbage();
     total_garbage += garbage;

     if (region->is_empty()) {
       free_regions++;
       free += ShenandoahHeapRegion::region_size_bytes();
     } else if (region->is_regular()) {
       if (!region->has_live()) {
         // We can recycle it right away and put it in the free set.
         immediate_regions++;
         immediate_garbage += garbage;
         region->make_trash_immediate();
       } else {
         // This is our candidate for later consideration.
         candidates[cand_idx]._region = region;
         candidates[cand_idx]._garbage = garbage;
         cand_idx++;
       }
     } else if (region->is_humongous_start()) {
       // Reclaim humongous regions here, and count them as the immediate garbage
 #ifdef ASSERT
       bool reg_live = region->has_live();
       bool bm_live = ctx->is_marked(oop(region->bottom()));
       assert(reg_live == bm_live,
              "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
              BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
 #endif
       if (!region->has_live()) {
         heap->trash_humongous_region_at(region);

         // Count only the start. Continuations would be counted on "trash" path
         immediate_regions++;
         immediate_garbage += garbage;
       }
     } else if (region->is_trash()) {
       // Count in just trashed collection set, during coalesced CM-with-UR
       immediate_regions++;
       immediate_garbage += garbage;
     }
   }

   // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
   // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.

   assert (immediate_garbage <= total_garbage,
           "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s",
           byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage),
           byte_size_in_proper_unit(total_garbage),     proper_unit_for_byte_size(total_garbage));

   size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage);

   if (immediate_percent <= ShenandoahImmediateThreshold) {
     choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
   }

   size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage);

   size_t collectable_garbage = collection_set->garbage() + immediate_garbage;
   size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage);

   log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
                      "Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
                      "CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%)",

                      byte_size_in_proper_unit(collectable_garbage),
                      proper_unit_for_byte_size(collectable_garbage),
                      collectable_garbage_percent,

                      byte_size_in_proper_unit(immediate_garbage),
                      proper_unit_for_byte_size(immediate_garbage),
                      immediate_percent,

                      byte_size_in_proper_unit(collection_set->garbage()),
                      proper_unit_for_byte_size(collection_set->garbage()),
                      cset_percent);
 }

 void ShenandoahHeuristics::record_cycle_start() {
   _cycle_start = os::elapsedTime();
 }

 void ShenandoahHeuristics::record_cycle_end() {
   _last_cycle_end = os::elapsedTime();
 }

 bool ShenandoahHeuristics::should_start_gc() const {
   // Perform GC to cleanup metaspace
   if (has_metaspace_oom()) {
     // Some of vmTestbase/metaspace tests depend on following line to count GC cycles
     log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold));
     return true;
   }

   if (ShenandoahGuaranteedGCInterval > 0) {
     double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
     if (last_time_ms > ShenandoahGuaranteedGCInterval) {
       log_info(gc)("Trigger: Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
                    last_time_ms, ShenandoahGuaranteedGCInterval);
       return true;
     }
   }

   return false;
 }

 bool ShenandoahHeuristics::should_degenerate_cycle() {
   return _degenerated_cycles_in_a_row <= ShenandoahFullGCThreshold;
 }

 void ShenandoahHeuristics::adjust_penalty(intx step) {
   assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
           "In range before adjustment: " INTX_FORMAT, _gc_time_penalties);

   intx new_val = _gc_time_penalties + step;
   if (new_val < 0) {
     new_val = 0;
   }
   if (new_val > 100) {
     new_val = 100;
   }
   _gc_time_penalties = new_val;

   assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
           "In range after adjustment: " INTX_FORMAT, _gc_time_penalties);
 }

 void ShenandoahHeuristics::record_success_concurrent() {
   _degenerated_cycles_in_a_row = 0;
   _successful_cycles_in_a_row++;

   _gc_time_history->add(time_since_last_gc());
   _gc_times_learned++;

   adjust_penalty(Concurrent_Adjust);
 }

 void ShenandoahHeuristics::record_success_degenerated() {
   _degenerated_cycles_in_a_row++;
   _successful_cycles_in_a_row = 0;

   adjust_penalty(Degenerated_Penalty);
 }

 void ShenandoahHeuristics::record_success_full() {
   _degenerated_cycles_in_a_row = 0;
   _successful_cycles_in_a_row++;

   adjust_penalty(Full_Penalty);
 }

 void ShenandoahHeuristics::record_allocation_failure_gc() {
   // Do nothing.
 }

 void ShenandoahHeuristics::record_requested_gc() {
   // Assume users call System.gc() when external state changes significantly,
   // which forces us to re-learn the GC timings and allocation rates.
   _gc_times_learned = 0;
 }

 bool ShenandoahHeuristics::can_process_references() {
   if (ShenandoahRefProcFrequency == 0) return false;
   return true;
 }

 bool ShenandoahHeuristics::should_process_references() {
   if (!can_process_references()) return false;
   size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter();
   // Process references every Nth GC cycle.
   return cycle % ShenandoahRefProcFrequency == 0;
 }

 bool ShenandoahHeuristics::can_unload_classes() {
   if (!ClassUnloading) return false;
   return true;
 }

 bool ShenandoahHeuristics::can_unload_classes_normal() {
   if (!can_unload_classes()) return false;
   if (has_metaspace_oom()) return true;
   if (!ClassUnloadingWithConcurrentMark) return false;
   if (ShenandoahUnloadClassesFrequency == 0) return false;
   return true;
 }

 bool ShenandoahHeuristics::should_unload_classes() {
   if (!can_unload_classes_normal()) return false;
   if (has_metaspace_oom()) return true;
   size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter();
   // Unload classes every Nth GC cycle.
   // This should not happen in the same cycle as process_references to amortize costs.
   // Offsetting by one is enough to break the rendezvous when periods are equal.
   // When periods are not equal, offsetting by one is just as good as any other guess.
   return (cycle + 1) % ShenandoahUnloadClassesFrequency == 0;
 }

 void ShenandoahHeuristics::initialize() {
   // Nothing to do by default.
 }

 double ShenandoahHeuristics::time_since_last_gc() const {
   return os::elapsedTime() - _cycle_start;
 }
	/*
	* Copyright (c) 2018, 2020, Red Hat, Inc. All rights reserved.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*
	*/

	#include "precompiled.hpp"

	#include "gc/shared/gcCause.hpp"
	#include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
	#include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
	#include "gc/shenandoah/shenandoahHeap.inline.hpp"
	#include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
	#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
	#include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
	#include "logging/log.hpp"
	#include "logging/logTag.hpp"

	int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) {
	if (a._garbage > b._garbage)
	return -1;
	else if (a._garbage < b._garbage)
	return 1;
	else return 0;
	}

	ShenandoahHeuristics::ShenandoahHeuristics() :
	_region_data(NULL),
	_degenerated_cycles_in_a_row(0),
	_successful_cycles_in_a_row(0),
	_cycle_start(os::elapsedTime()),
	_last_cycle_end(0),
	_gc_times_learned(0),
	_gc_time_penalties(0),
	_gc_time_history(new TruncatedSeq(5)),
	_metaspace_oom()
	{
	// No unloading during concurrent mark? Communicate that to heuristics
	if (!ClassUnloadingWithConcurrentMark) {
	FLAG_SET_DEFAULT(ShenandoahUnloadClassesFrequency, 0);
	}

	size_t num_regions = ShenandoahHeap::heap()->num_regions();
	assert(num_regions > 0, "Sanity");

	_region_data = NEW_C_HEAP_ARRAY(RegionData, num_regions, mtGC);
	}

	ShenandoahHeuristics::~ShenandoahHeuristics() {
	FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
	}

	void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
	assert(collection_set->count() == 0, "Must be empty");

	ShenandoahHeap* heap = ShenandoahHeap::heap();

	// Check all pinned regions have updated status before choosing the collection set.
	heap->assert_pinned_region_status();

	// Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.

	size_t num_regions = heap->num_regions();

	RegionData* candidates = _region_data;

	size_t cand_idx = 0;

	size_t total_garbage = 0;

	size_t immediate_garbage = 0;
	size_t immediate_regions = 0;

	size_t free = 0;
	size_t free_regions = 0;

	ShenandoahMarkingContext* const ctx = heap->complete_marking_context();

	for (size_t i = 0; i < num_regions; i++) {
	ShenandoahHeapRegion* region = heap->get_region(i);

	size_t garbage = region->garbage();
	total_garbage += garbage;

	if (region->is_empty()) {
	free_regions++;
	free += ShenandoahHeapRegion::region_size_bytes();
	} else if (region->is_regular()) {
	if (!region->has_live()) {
	// We can recycle it right away and put it in the free set.
	immediate_regions++;
	immediate_garbage += garbage;
	region->make_trash_immediate();
	} else {
	// This is our candidate for later consideration.
	candidates[cand_idx]._region = region;
	candidates[cand_idx]._garbage = garbage;
	cand_idx++;
	}
	} else if (region->is_humongous_start()) {
	// Reclaim humongous regions here, and count them as the immediate garbage
	#ifdef ASSERT
	bool reg_live = region->has_live();
	bool bm_live = ctx->is_marked(oop(region->bottom()));
	assert(reg_live == bm_live,
	"Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
	BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
	#endif
	if (!region->has_live()) {
	heap->trash_humongous_region_at(region);

	// Count only the start. Continuations would be counted on "trash" path
	immediate_regions++;
	immediate_garbage += garbage;
	}
	} else if (region->is_trash()) {
	// Count in just trashed collection set, during coalesced CM-with-UR
	immediate_regions++;
	immediate_garbage += garbage;
	}
	}

	// Step 2. Look back at garbage statistics, and decide if we want to collect anything,
	// given the amount of immediately reclaimable garbage. If we do, figure out the collection set.

	assert (immediate_garbage <= total_garbage,
	"Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s",
	byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage),
	byte_size_in_proper_unit(total_garbage), proper_unit_for_byte_size(total_garbage));

	size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage);

	if (immediate_percent <= ShenandoahImmediateThreshold) {
	choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
	}

	size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage);

	size_t collectable_garbage = collection_set->garbage() + immediate_garbage;
	size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage);

	log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
	"Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
	"CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%)",

	byte_size_in_proper_unit(collectable_garbage),
	proper_unit_for_byte_size(collectable_garbage),
	collectable_garbage_percent,

	byte_size_in_proper_unit(immediate_garbage),
	proper_unit_for_byte_size(immediate_garbage),
	immediate_percent,

	byte_size_in_proper_unit(collection_set->garbage()),
	proper_unit_for_byte_size(collection_set->garbage()),
	cset_percent);
	}

	void ShenandoahHeuristics::record_cycle_start() {
	_cycle_start = os::elapsedTime();
	}

	void ShenandoahHeuristics::record_cycle_end() {
	_last_cycle_end = os::elapsedTime();
	}

	bool ShenandoahHeuristics::should_start_gc() const {
	// Perform GC to cleanup metaspace
	if (has_metaspace_oom()) {
	// Some of vmTestbase/metaspace tests depend on following line to count GC cycles
	log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold));
	return true;
	}

	if (ShenandoahGuaranteedGCInterval > 0) {
	double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
	if (last_time_ms > ShenandoahGuaranteedGCInterval) {
	log_info(gc)("Trigger: Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
	last_time_ms, ShenandoahGuaranteedGCInterval);
	return true;
	}
	}

	return false;
	}

	bool ShenandoahHeuristics::should_degenerate_cycle() {
	return _degenerated_cycles_in_a_row <= ShenandoahFullGCThreshold;
	}

	void ShenandoahHeuristics::adjust_penalty(intx step) {
	assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
	"In range before adjustment: " INTX_FORMAT, _gc_time_penalties);

	intx new_val = _gc_time_penalties + step;
	if (new_val < 0) {
	new_val = 0;
	}
	if (new_val > 100) {
	new_val = 100;
	}
	_gc_time_penalties = new_val;

	assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
	"In range after adjustment: " INTX_FORMAT, _gc_time_penalties);
	}

	void ShenandoahHeuristics::record_success_concurrent() {
	_degenerated_cycles_in_a_row = 0;
	_successful_cycles_in_a_row++;

	_gc_time_history->add(time_since_last_gc());
	_gc_times_learned++;

	adjust_penalty(Concurrent_Adjust);
	}

	void ShenandoahHeuristics::record_success_degenerated() {
	_degenerated_cycles_in_a_row++;
	_successful_cycles_in_a_row = 0;

	adjust_penalty(Degenerated_Penalty);
	}

	void ShenandoahHeuristics::record_success_full() {
	_degenerated_cycles_in_a_row = 0;
	_successful_cycles_in_a_row++;

	adjust_penalty(Full_Penalty);
	}

	void ShenandoahHeuristics::record_allocation_failure_gc() {
	// Do nothing.
	}

	void ShenandoahHeuristics::record_requested_gc() {
	// Assume users call System.gc() when external state changes significantly,
	// which forces us to re-learn the GC timings and allocation rates.
	_gc_times_learned = 0;
	}

	bool ShenandoahHeuristics::can_process_references() {
	if (ShenandoahRefProcFrequency == 0) return false;
	return true;
	}

	bool ShenandoahHeuristics::should_process_references() {
	if (!can_process_references()) return false;
	size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter();
	// Process references every Nth GC cycle.
	return cycle % ShenandoahRefProcFrequency == 0;
	}

	bool ShenandoahHeuristics::can_unload_classes() {
	if (!ClassUnloading) return false;
	return true;
	}

	bool ShenandoahHeuristics::can_unload_classes_normal() {
	if (!can_unload_classes()) return false;
	if (has_metaspace_oom()) return true;
	if (!ClassUnloadingWithConcurrentMark) return false;
	if (ShenandoahUnloadClassesFrequency == 0) return false;
	return true;
	}

	bool ShenandoahHeuristics::should_unload_classes() {
	if (!can_unload_classes_normal()) return false;
	if (has_metaspace_oom()) return true;
	size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter();
	// Unload classes every Nth GC cycle.
	// This should not happen in the same cycle as process_references to amortize costs.
	// Offsetting by one is enough to break the rendezvous when periods are equal.
	// When periods are not equal, offsetting by one is just as good as any other guess.
	return (cycle + 1) % ShenandoahUnloadClassesFrequency == 0;
	}

	void ShenandoahHeuristics::initialize() {
	// Nothing to do by default.
	}

	double ShenandoahHeuristics::time_since_last_gc() const {
	return os::elapsedTime() - _cycle_start;
	}