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8205921: Optimizing best-of-2 work stealing queue selection

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Bias towards stealing from queues that we recently successfully stole from to decrease the number of unsuccessful steal attempts.

Co-authored-by: Thomas Schatzl <thomas.schatzl@oracle.com>
Reviewed-by: eosterlund, kbarrett
This commit is contained in:
Zhengyu Gu 2018-08-03 11:06:10 +02:00
parent c4faf01f86
commit 4555c28590
19 changed files with 119 additions and 93 deletions
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36
src/hotspot/share/gc/shared/taskqueue.hpp
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@ -26,6 +26,7 @@
#define SHARE_VM_GC_SHARED_TASKQUEUE_HPP
#include "memory/allocation.hpp"
#include "memory/padded.hpp"
#include "oops/oopsHierarchy.hpp"
#include "utilities/ostream.hpp"
#include "utilities/stack.hpp"
@ -298,12 +299,30 @@ public:
template<typename Fn> void iterate(Fn fn);
private:
DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, 0);
// Element array.
volatile E* _elems;
DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(E*));
// Queue owner local variables. Not to be accessed by other threads.
static const uint InvalidQueueId = uint(-1);
uint _last_stolen_queue_id; // The id of the queue we last stole from
int _seed; // Current random seed used for selecting a random queue during stealing.
DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, sizeof(uint) + sizeof(int));
public:
int next_random_queue_id();
void set_last_stolen_queue_id(uint id) { _last_stolen_queue_id = id; }
uint last_stolen_queue_id() const { return _last_stolen_queue_id; }
bool is_last_stolen_queue_id_valid() const { return _last_stolen_queue_id != InvalidQueueId; }
void invalidate_last_stolen_queue_id() { _last_stolen_queue_id = InvalidQueueId; }
};
template<class E, MEMFLAGS F, unsigned int N>
GenericTaskQueue<E, F, N>::GenericTaskQueue() {
GenericTaskQueue<E, F, N>::GenericTaskQueue() : _last_stolen_queue_id(InvalidQueueId), _seed(17 /* random number */) {
assert(sizeof(Age) == sizeof(size_t), "Depends on this.");
}
@ -348,8 +367,6 @@ private:
};
class TaskQueueSetSuper {
protected:
static int randomParkAndMiller(int* seed0);
public:
// Returns "true" if some TaskQueue in the set contains a task.
virtual bool peek() = 0;
@ -367,22 +384,19 @@ private:
uint _n;
T** _queues;
bool steal_best_of_2(uint queue_num, int* seed, E& t);
bool steal_best_of_2(uint queue_num, E& t);
public:
GenericTaskQueueSet(int n);
GenericTaskQueueSet(uint n);
~GenericTaskQueueSet();
void register_queue(uint i, T* q);
T* queue(uint n);
// The thread with queue number "queue_num" (and whose random number seed is
// at "seed") is trying to steal a task from some other queue. (It may try
// several queues, according to some configuration parameter.) If some steal
// succeeds, returns "true" and sets "t" to the stolen task, otherwise returns
// false.
bool steal(uint queue_num, int* seed, E& t);
// Try to steal a task from some other queue than queue_num. It may perform several attempts at doing so.
// Returns if stealing succeeds, and sets "t" to the stolen task.
bool steal(uint queue_num, E& t);
bool peek();