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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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#include "gc_implementation/g1/collectionSetChooser.hpp"
#include "gc_implementation/g1/g1MMUTracker.hpp"
#include "memory/collectorPolicy.hpp"
// A G1CollectorPolicy makes policy decisions that determine the
// characteristics of the collector. Examples include:
// * choice of collection set.
// * when to collect.
class HeapRegion;
class CollectionSetChooser;
class G1GCPhaseTimes;
// TraceGen0Time collects data on _both_ young and mixed evacuation pauses
// (the latter may contain non-young regions - i.e. regions that are
// technically in Gen1) while TraceGen1Time collects data about full GCs.
private:
unsigned _young_pause_num;
unsigned _mixed_pause_num;
public:
void record_start_collection(double time_to_stop_the_world_ms);
void record_yield_time(double yield_time_ms);
void increment_young_collection_count();
void increment_mixed_collection_count();
void print() const;
};
private:
public:
void record_full_collection(double full_gc_time_ms);
void print() const;
};
// There are three command line options related to the young gen size:
// NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
// just a short form for NewSize==MaxNewSize). G1 will use its internal
// heuristics to calculate the actual young gen size, so these options
// basically only limit the range within which G1 can pick a young gen
// size. Also, these are general options taking byte sizes. G1 will
// internally work with a number of regions instead. So, some rounding
// will occur.
//
// If nothing related to the the young gen size is set on the command
// line we should allow the young gen to be between G1NewSizePercent
// and G1MaxNewSizePercent of the heap size. This means that every time
// the heap size changes, the limits for the young gen size will be
// recalculated.
//
// If only -XX:NewSize is set we should use the specified value as the
// minimum size for young gen. Still using G1MaxNewSizePercent of the
// heap as maximum.
//
// If only -XX:MaxNewSize is set we should use the specified value as the
// maximum size for young gen. Still using G1NewSizePercent of the heap
// as minimum.
//
// If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
// No updates when the heap size changes. There is a special case when
// NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
// different heuristic for calculating the collection set when we do mixed
// collection.
//
// If only -XX:NewRatio is set we should use the specified ratio of the heap
// as both min and max. This will be interpreted as "fixed" just like the
// NewSize==MaxNewSize case above. But we will update the min and max
// everytime the heap size changes.
//
// NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
// combined with either NewSize or MaxNewSize. (A warning message is printed.)
private:
enum SizerKind {
};
bool _adaptive_size;
public:
return _min_desired_young_length;
}
return _max_desired_young_length;
}
bool adaptive_young_list_length() {
return _adaptive_size;
}
};
private:
// either equal to the number of parallel threads, if ParallelGCThreads
// has been set, or 1 otherwise
int _parallel_gc_threads;
// The number of GC threads currently active.
enum SomePrivateConstants {
};
void initialize_flags();
void initialize_all() {
}
double _full_collection_start_sec;
// These exclude marking times.
double _stop_world_start;
// indicates whether we are in young or mixed GC mode
bool _gcs_are_young;
// The max number of regions we can extend the eden by while the GC
// locker is active. This should be >= _young_list_target_length;
bool _last_gc_was_young;
bool _during_marking;
bool _in_marking_window;
bool _in_marking_window_im;
// add here any more surv rate groups
double _gc_overhead_perc;
double _reserve_factor;
bool during_marking() {
return _during_marking;
}
private:
enum PredictionConstants {
};
double _prev_collection_pause_end_ms;
double _sigma;
// A function that prevents us putting too much stock in small sample
// sets. Returns a number between 2.0 and 1.0, depending on the number
// of samples. 5 or more samples yields one; fewer scales linearly from
// 2.0 at 1 sample to 1.0 at 5.
}
}
#ifndef PRODUCT
#endif // PRODUCT
void adjust_concurrent_refinement(double update_rs_time,
double update_rs_processed_buffers,
double goal_ms);
double _pause_time_target_ms;
public:
// Accessors
}
}
#ifndef PRODUCT
bool verify_young_ages();
#endif // PRODUCT
}
}
}
double predict_alloc_rate_ms() {
return get_new_prediction(_alloc_rate_ms_seq);
}
double predict_cost_per_card_ms() {
return get_new_prediction(_cost_per_card_ms_seq);
}
return (double) pending_cards * predict_cost_per_card_ms();
}
double predict_young_cards_per_entry_ratio() {
}
double predict_mixed_cards_per_entry_ratio() {
return predict_young_cards_per_entry_ratio();
} else {
}
}
}
}
if (gcs_are_young()) {
} else {
return predict_mixed_rs_scan_time_ms(card_num);
}
}
} else {
return (double) (card_num *
}
}
return (1.1 * (double) bytes_to_copy) *
} else {
return (double) bytes_to_copy *
}
}
if (_in_marking_window && !_in_marking_window_im) {
} else {
return (double) bytes_to_copy *
}
}
double predict_constant_other_time_ms() {
}
return (double) young_num *
}
return (double) non_young_num *
}
double predict_survivor_regions_evac_time();
void cset_regions_freed() {
// also call it on any more surv rate groups
}
return _mmu_tracker;
}
double max_pause_time_ms() {
}
double predict_remark_time_ms() {
}
double predict_cleanup_time_ms() {
}
// Returns an estimate of the survival rate of the region at yg-age
// "yg_age".
if (pred > 1.0)
pred = 1.0;
return pred;
}
}
}
private:
// Statistics kept per GC stoppage, pause or full.
// Add a new GC of the given duration and end time to the record.
// The head of the list (via "next_in_collection_set()") representing the
// current collection set. Set from the incrementally built collection
// set at the start of the pause.
// The number of bytes in the collection set before the pause. Set from
// the incrementally built collection set at the start of an evacuation
// pause, and incremented in finalize_cset() when adding old regions
// (if any) to the collection set.
// The number of bytes copied during the GC.
// The associated information that is maintained while the incremental
// collection set is being built with young regions. Used to populate
// the recorded info for the evacuation pause.
enum CSetBuildType {
};
// The head of the incrementally built collection set.
// The tail of the incrementally built collection set.
// The number of bytes in the incrementally built collection set.
// Used to set _collection_set_bytes_used_before at the start of
// an evacuation pause.
// Used to record the highest end of heap region in collection set
// The RSet lengths recorded for regions in the CSet. It is updated
// by the thread that adds a new region to the CSet. We assume that
// only one thread can be allocating a new CSet region (currently,
// it does so after taking the Heap_lock) hence no need to
// synchronize updates to this field.
// A concurrent refinement thread periodcially samples the young
// region RSets and needs to update _inc_cset_recorded_rs_lengths as
// the RSets grow. Instead of having to syncronize updates to that
// field we accumulate them in this field and add it to
// _inc_cset_recorded_rs_lengths_diffs at the start of a GC.
// The predicted elapsed time it will take to collect the regions in
// the CSet. This is updated by the thread that adds a new region to
// the CSet. See the comment for _inc_cset_recorded_rs_lengths about
// MT-safety assumptions.
// See the comment for _inc_cset_recorded_rs_lengths_diffs.
// Stash a pointer to the g1 heap.
// The ratio of gc time to elapsed time, computed over recent pauses.
double _recent_avg_pause_time_ratio;
double recent_avg_pause_time_ratio() {
return _recent_avg_pause_time_ratio;
}
// At the end of a pause we check the heap occupancy and we decide
// whether we will start a marking cycle during the next pause. If
// we decide that we want to do that, we will set this parameter to
// true. So, this parameter will stay true between the end of a
// pause and the beginning of a subsequent pause (not necessarily
// the next one, see the comments on the next field) when we decide
// that we will indeed start a marking cycle and do the initial-mark
// work.
volatile bool _initiate_conc_mark_if_possible;
// If initiate_conc_mark_if_possible() is set at the beginning of a
// pause, it is a suggestion that the pause should start a marking
// cycle by doing the initial-mark work. However, it is possible
// that the concurrent marking thread is still finishing up the
// previous marking cycle (e.g., clearing the next marking
// bitmap). If that is the case we cannot start a new cycle and
// we'll have to wait for the concurrent marking thread to finish
// what it is doing. In this case we will postpone the marking cycle
// initiation decision for the next pause. When we eventually decide
// to start a cycle, we will set _during_initial_mark_pause which
// will stay true until the end of the initial-mark pause and it's
// the condition that indicates that a pause is doing the
// initial-mark work.
volatile bool _during_initial_mark_pause;
bool _last_young_gc;
// This set of variables tracks the collector efficiency, in order to
// determine whether we should initiate a new marking.
double _cur_mark_stop_world_time_ms;
double _mark_remark_start_sec;
double _mark_cleanup_start_sec;
// Update the young list target length either by setting it to the
// desired fixed value or by calculating it using G1's pause
// prediction model. If no rs_lengths parameter is passed, predict
// the RS lengths using the prediction model, otherwise use the
// given rs_lengths as the prediction.
// Calculate and return the minimum desired young list target
// length. This is the minimum desired young list length according
// to the user's inputs.
// Calculate and return the maximum desired young list target
// length. This is the maximum desired young list length according
// to the user's inputs.
// Calculate and return the maximum young list target length that
// can fit into the pause time goal. The parameters are: rs_lengths
// represent the prediction of how large the young RSet lengths will
// be, base_min_length is the alreay existing number of regions in
// the young list, min_length and max_length are the desired min and
// max young list length according to the user's inputs.
// Check whether a given young length (young_length) fits into the
// given target pause time and whether the prediction for the amount
// of objects to be copied for the given length will fit into the
// given free space (expressed by base_free_regions). It is used by
// calculate_young_list_target_length().
// Calculate the minimum number of old regions we'll add to the CSet
// during a mixed GC.
// Calculate the maximum number of old regions we'll add to the CSet
// during a mixed GC.
// Returns the given amount of uncollected reclaimable space
// as a percentage of the current heap capacity.
public:
return CollectorPolicy::G1CollectorPolicyKind;
}
// Check the current value of the young list RSet lengths and
// compare it against the last prediction. If the current value is
// higher, recalculate the young list target length prediction.
// This should be called after the heap is resized.
void init();
// Create jstat counters for the policy.
virtual void initialize_gc_policy_counters();
bool is_tlab,
bool* gc_overhead_limit_was_exceeded);
// This method controls how a collector handles one or more
// of its generations being fully allocated.
bool is_tlab);
// Record the start and end of an evacuation pause.
void record_collection_pause_start(double start_time_sec);
// Record the start and end of a full collection.
void record_full_collection_start();
void record_full_collection_end();
// Must currently be called while the world is stopped.
void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
// Record start and end of remark.
// Record start, end, and completion of cleanup.
// Records the information about the heap size for reporting in
// print_detailed_heap_transition
void record_heap_size_info_at_start();
// Print heap sizing transition (with less and more detail).
void print_heap_transition();
void print_detailed_heap_transition();
void record_stop_world_start();
void record_concurrent_pause();
// Record how much space we copied during a GC. This is typically
// called when a GC alloc region is being retired.
}
// The amount of space we copied during a GC.
return _bytes_copied_during_gc;
}
// Determine whether there are candidate regions so that the
// next GC should be mixed. The two action strings are used
// in the ergo output when the method returns true or false.
bool next_gc_should_be_mixed(const char* true_action_str,
const char* false_action_str);
// Choose a new collection set. Marks the chosen regions as being
// "in_collection_set", and links them together. The head and number of
// the collection set are available via access methods.
// The head of the list (via "next_in_collection_set()") representing the
// current collection set.
// Add old region "hr" to the CSet.
// Incremental CSet Support
// The head of the incrementally built collection set.
// The tail of the incrementally built collection set.
// Initialize incremental collection set info.
void start_incremental_cset_building();
// Perform any final calculations on the incremental CSet fields
// before we can use them.
void clear_incremental_cset() {
}
// Stop adding regions to the incremental collection set
// Add information about hr to the aggregated information for the
// incrementally built collection set.
// Update information about hr in the aggregated information for
// the incrementally built collection set.
private:
// Update the incremental cset information when adding a region
// (should not be called directly).
public:
// Add hr to the LHS of the incremental collection set.
// Add hr to the RHS of the incremental collection set.
#ifndef PRODUCT
#endif // !PRODUCT
// This sets the initiate_conc_mark_if_possible() flag to start a
// new cycle, as long as we are not already in one. It's best if it
// is called during a safepoint when the test whether a cycle is in
// progress or not is stable.
// This is called at the very beginning of an evacuation pause (it
// has to be the first thing that the pause does). If
// initiate_conc_mark_if_possible() is true, and the concurrent
// marking thread has completed its work during the previous cycle,
// it will set during_initial_mark_pause() to so that the pause does
// the initial-mark work and start a marking cycle.
void decide_on_conc_mark_initiation();
// If an expansion would be appropriate, because recent GC overhead had
// exceeded the desired limit, return an amount to expand by.
// Print tracing information.
void print_tracing_info() const;
// Print stats on young survival ratio
void print_yg_surv_rate_info() const;
if (is_survivors) {
} else {
}
// do that for any other surv rate groups
}
bool is_young_list_full() {
return young_list_length >= young_list_target_length;
}
bool can_expand_young_list() {
return young_list_length < young_list_max_length;
}
return _young_list_max_length;
}
bool gcs_are_young() {
return _gcs_are_young;
}
}
bool adaptive_young_list_length() {
return _young_gen_sizer->adaptive_young_list_length();
}
private:
//
// Survivor regions policy.
//
// Current tenuring threshold, set to 0 if the collector reaches the
// maximum amount of suvivors regions.
int _tenuring_threshold;
// The limit on the number of regions allocated for survivors.
// For reporting purposes.
// The amount of survor regions after a collection.
// List of survivor regions.
public:
inline GCAllocPurpose
return GCAllocForSurvived;
} else {
return GCAllocForTenured;
}
}
return purpose == GCAllocForSurvived;
}
// The limit on regions for a particular purpose is reached.
if (purpose == GCAllocForSurvived) {
_tenuring_threshold = 0;
}
}
void note_start_adding_survivor_regions() {
}
void note_stop_adding_survivor_regions() {
}
HeapRegion* tail) {
}
return _recorded_survivor_regions;
}
}
void update_max_gc_locker_expansion();
// Calculates survivor space parameters.
void update_survivors_policy();
};
// This should move to some place more general...
// If we have "n" measurements, and we've kept track of their "sum" and the
// "sum_of_squares" of the measurements, this returns the variance of the
// sequence.
double n_d = (double)n;
}
#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP