| 187 |
|
* workers to start scanning -- see below.) Both a successful pop |
| 188 |
|
* and poll mainly entail a CAS of a slot from non-null to null. |
| 189 |
|
* |
| 190 |
< |
* The pop operation (always performed by owener) is: |
| 190 |
> |
* The pop operation (always performed by owner) is: |
| 191 |
|
* if ((base != top) and |
| 192 |
|
* (the task at top slot is not null) and |
| 193 |
|
* (CAS slot to null)) |
| 393 |
|
* power-of-two hash table, expanding as needed. The seedIndex |
| 394 |
|
* increment ensures no collisions until a resize is needed or a |
| 395 |
|
* worker is deregistered and replaced, and thereafter keeps |
| 396 |
< |
* probablility of collision low. We cannot use |
| 396 |
> |
* probability of collision low. We cannot use |
| 397 |
|
* ThreadLocalRandom.getProbe() for similar purposes here because |
| 398 |
|
* the thread has not started yet, but do so for creating |
| 399 |
|
* submission queues for existing external threads. |
| 400 |
|
* |
| 401 |
< |
* Deactivation and waiting. Queuing enounters several intrinsic |
| 401 |
> |
* Deactivation and waiting. Queuing encounters several intrinsic |
| 402 |
|
* races; most notably that a task-producing thread can miss |
| 403 |
|
* seeing (and signalling) another thread that gave up looking for |
| 404 |
|
* work but has not yet entered the wait queue. When a worker |
| 411 |
|
* scanning process after successful enqueuing until again stable. |
| 412 |
|
* In this state, the worker cannot take/run a task it sees until |
| 413 |
|
* it is released from the queue, so the worker itself eventually |
| 414 |
< |
* tries to release itself or any succcessor (see tryRelease). |
| 414 |
> |
* tries to release itself or any successor (see tryRelease). |
| 415 |
|
* Otherwise, upon an empty scan, a deactivated worker uses an |
| 416 |
|
* adaptive local spin construction (see awaitWork) before |
| 417 |
|
* blocking (via park). Note the unusual conventions about |
| 516 |
|
* |
| 517 |
|
* Helping actions for CountedCompleters do not require tracking |
| 518 |
|
* currentJoins: Method helpComplete takes and executes any task |
| 519 |
< |
* with the same root as the task being waited on (prefering local |
| 520 |
< |
* pops to non-local polls). However, this still entails some |
| 521 |
< |
* traversal of completer chains, so is less efficient than using |
| 522 |
< |
* CountedCompleters without explicit joins. |
| 519 |
> |
* with the same root as the task being waited on (preferring |
| 520 |
> |
* local pops to non-local polls). However, this still entails |
| 521 |
> |
* some traversal of completer chains, so is less efficient than |
| 522 |
> |
* using CountedCompleters without explicit joins. |
| 523 |
|
* |
| 524 |
|
* Compensation does not aim to keep exactly the target |
| 525 |
|
* parallelism number of unblocked threads running at any given |
| 703 |
|
|
| 704 |
|
/** |
| 705 |
|
* Queues supporting work-stealing as well as external task |
| 706 |
< |
* submission. See above for dewscriptions and algorithms |
| 706 |
> |
* submission. See above for descriptions and algorithms. |
| 707 |
|
* Performance on most platforms is very sensitive to placement of |
| 708 |
|
* instances of both WorkQueues and their arrays -- we absolutely |
| 709 |
|
* do not want multiple WorkQueue instances or multiple queue |
| 1418 |
|
* |
| 1419 |
|
* @param c incoming ctl value, with total count negative and no |
| 1420 |
|
* idle workers. On CAS failure, c is refreshed and retried if |
| 1421 |
< |
* this holds (otherwise, a new worker is not neeeded). |
| 1421 |
> |
* this holds (otherwise, a new worker is not needed). |
| 1422 |
|
*/ |
| 1423 |
|
private void tryAddWorker(long c) { |
| 1424 |
|
boolean add = false; |
| 1609 |
|
|
| 1610 |
|
/** |
| 1611 |
|
* Scans for and tries to steal a top-level task. Scans start at a |
| 1612 |
< |
* random location, randomly moving on apparentl contention, |
| 1612 |
> |
* random location, randomly moving on apparent contention, |
| 1613 |
|
* otherwise continuing linearly until reaching two consecutive |
| 1614 |
|
* empty passes over all queues with the same checksum (summing |
| 1615 |
|
* each base index of each queue, that moves on each steal), at |
| 1707 |
|
(j = pred & SMASK) < ws.length && |
| 1708 |
|
(v = ws[j]) != null && // see if pred parking |
| 1709 |
|
(v.parker == null || v.scanState >= 0)) |
| 1710 |
< |
spins = SPINS; // continue spinnning |
| 1710 |
> |
spins = SPINS; // continue spinning |
| 1711 |
|
else if ((s = w.nsteals) != 0) { |
| 1712 |
|
w.nsteals = 0; // collect steals |
| 1713 |
|
U.getAndAddLong(this, STEALCOUNT, s); |
| 1765 |
|
* values). |
| 1766 |
|
* |
| 1767 |
|
* @param w caller |
| 1768 |
< |
* @param maxTasks if non-sero, the maximum number of other tasks to run |
| 1768 |
> |
* @param maxTasks if non-zero, the maximum number of other tasks to run |
| 1769 |
|
* @return task status on exit |
| 1770 |
|
*/ |
| 1771 |
|
final int helpComplete(WorkQueue w, CountedCompleter<?> task, |
