--- a/src/hotspot/share/gc/cms/yieldingWorkgroup.cpp Fri Nov 08 14:54:17 2019 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,399 +0,0 @@
-/*
- * Copyright (c) 2005, 2019, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * 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/cms/yieldingWorkgroup.hpp"
-#include "gc/shared/gcId.hpp"
-#include "utilities/macros.hpp"
-
-YieldingFlexibleGangWorker::YieldingFlexibleGangWorker(YieldingFlexibleWorkGang* gang, int id)
- : AbstractGangWorker(gang, id) {}
-
-YieldingFlexibleWorkGang::YieldingFlexibleWorkGang(
- const char* name, uint workers, bool are_GC_task_threads) :
- AbstractWorkGang(name, workers, are_GC_task_threads, false),
- _yielded_workers(0),
- _started_workers(0),
- _finished_workers(0),
- _sequence_number(0),
- _task(NULL) {
-
- // Other initialization.
- _monitor = new Monitor(/* priority */ Mutex::leaf,
- /* name */ "WorkGroup monitor",
- /* allow_vm_block */ are_GC_task_threads,
- Monitor::_safepoint_check_never);
-
- assert(monitor() != NULL, "Failed to allocate monitor");
-}
-
-AbstractGangWorker* YieldingFlexibleWorkGang::allocate_worker(uint which) {
- return new YieldingFlexibleGangWorker(this, which);
-}
-
-void YieldingFlexibleWorkGang::internal_worker_poll(YieldingWorkData* data) const {
- assert(data != NULL, "worker data is null");
- data->set_task(task());
- data->set_sequence_number(sequence_number());
-}
-
-void YieldingFlexibleWorkGang::internal_note_start() {
- assert(monitor()->owned_by_self(), "note_finish is an internal method");
- _started_workers += 1;
-}
-
-void YieldingFlexibleWorkGang::internal_note_finish() {
- assert(monitor()->owned_by_self(), "note_finish is an internal method");
- _finished_workers += 1;
-}
-
-// Run a task; returns when the task is done, or the workers yield,
-// or the task is aborted.
-// A task that has been yielded can be continued via this interface
-// by using the same task repeatedly as the argument to the call.
-// It is expected that the YieldingFlexibleGangTask carries the appropriate
-// continuation information used by workers to continue the task
-// from its last yield point. Thus, a completed task will return
-// immediately with no actual work having been done by the workers.
-/////////////////////
-// Implementatiuon notes: remove before checking XXX
-/*
-Each gang is working on a task at a certain time.
-Some subset of workers may have yielded and some may
-have finished their quota of work. Until this task has
-been completed, the workers are bound to that task.
-Once the task has been completed, the gang unbounds
-itself from the task.
-
-The yielding work gang thus exports two invokation
-interfaces: run_task() and continue_task(). The
-first is used to initiate a new task and bind it
-to the workers; the second is used to continue an
-already bound task that has yielded. Upon completion
-the binding is released and a new binding may be
-created.
-
-The shape of a yielding work gang is as follows:
-
-Overseer invokes run_task(*task).
- Lock gang monitor
- Check that there is no existing binding for the gang
- If so, abort with an error
- Else, create a new binding of this gang to the given task
- Set number of active workers (as asked)
- Notify workers that work is ready to be done
- [the requisite # workers would then start up
- and do the task]
- Wait on the monitor until either
- all work is completed or the task has yielded
- -- this is normally done through
- yielded + completed == active
- [completed workers are rest to idle state by overseer?]
- return appropriate status to caller
-
-Overseer invokes continue_task(*task),
- Lock gang monitor
- Check that task is the same as current binding
- If not, abort with an error
- Else, set the number of active workers as requested?
- Notify workers that they can continue from yield points
- New workers can also start up as required
- while satisfying the constraint that
- active + yielded does not exceed required number
- Wait (as above).
-
-NOTE: In the above, for simplicity in a first iteration
- our gangs will be of fixed population and will not
- therefore be flexible work gangs, just yielding work
- gangs. Once this works well, we will in a second
- iteration.refinement introduce flexibility into
- the work gang.
-
-NOTE: we can always create a new gang per each iteration
- in order to get the flexibility, but we will for now
- desist that simplified route.
-
- */
-/////////////////////
-void YieldingFlexibleWorkGang::start_task(YieldingFlexibleGangTask* new_task) {
- MutexLocker ml(monitor(), Mutex::_no_safepoint_check_flag);
- assert(task() == NULL, "Gang currently tied to a task");
- assert(new_task != NULL, "Null task");
- // Bind task to gang
- _task = new_task;
- new_task->set_gang(this); // Establish 2-way binding to support yielding
- _sequence_number++;
-
- uint requested_size = new_task->requested_size();
- if (requested_size != 0) {
- _active_workers = MIN2(requested_size, total_workers());
- } else {
- _active_workers = active_workers();
- }
- new_task->set_actual_size(_active_workers);
- new_task->set_for_termination(_active_workers);
-
- assert(_started_workers == 0, "Tabula rasa non");
- assert(_finished_workers == 0, "Tabula rasa non");
- assert(_yielded_workers == 0, "Tabula rasa non");
- yielding_task()->set_status(ACTIVE);
-
- // Wake up all the workers, the first few will get to work,
- // and the rest will go back to sleep
- monitor()->notify_all();
- wait_for_gang();
-}
-
-void YieldingFlexibleWorkGang::wait_for_gang() {
-
- assert(monitor()->owned_by_self(), "Data race");
- // Wait for task to complete or yield
- for (Status status = yielding_task()->status();
- status != COMPLETED && status != YIELDED && status != ABORTED;
- status = yielding_task()->status()) {
- assert(started_workers() <= active_workers(), "invariant");
- assert(finished_workers() <= active_workers(), "invariant");
- assert(yielded_workers() <= active_workers(), "invariant");
- monitor()->wait_without_safepoint_check();
- }
- switch (yielding_task()->status()) {
- case COMPLETED:
- case ABORTED: {
- assert(finished_workers() == active_workers(), "Inconsistent status");
- assert(yielded_workers() == 0, "Invariant");
- reset(); // for next task; gang<->task binding released
- break;
- }
- case YIELDED: {
- assert(yielded_workers() > 0, "Invariant");
- assert(yielded_workers() + finished_workers() == active_workers(),
- "Inconsistent counts");
- break;
- }
- case ACTIVE:
- case INACTIVE:
- case COMPLETING:
- case YIELDING:
- case ABORTING:
- default:
- ShouldNotReachHere();
- }
-}
-
-void YieldingFlexibleWorkGang::continue_task(
- YieldingFlexibleGangTask* gang_task) {
-
- MutexLocker ml(monitor(), Mutex::_no_safepoint_check_flag);
- assert(task() != NULL && task() == gang_task, "Incorrect usage");
- assert(_started_workers == _active_workers, "Precondition");
- assert(_yielded_workers > 0 && yielding_task()->status() == YIELDED,
- "Else why are we calling continue_task()");
- // Restart the yielded gang workers
- yielding_task()->set_status(ACTIVE);
- monitor()->notify_all();
- wait_for_gang();
-}
-
-void YieldingFlexibleWorkGang::reset() {
- _started_workers = 0;
- _finished_workers = 0;
- yielding_task()->set_gang(NULL);
- _task = NULL; // unbind gang from task
-}
-
-void YieldingFlexibleWorkGang::yield() {
- assert(task() != NULL, "Inconsistency; should have task binding");
- MutexLocker ml(monitor(), Mutex::_no_safepoint_check_flag);
- assert(yielded_workers() < active_workers(), "Consistency check");
- if (yielding_task()->status() == ABORTING) {
- // Do not yield; we need to abort as soon as possible
- // XXX NOTE: This can cause a performance pathology in the
- // current implementation in Mustang, as of today, and
- // pre-Mustang in that as soon as an overflow occurs,
- // yields will not be honoured. The right way to proceed
- // of course is to fix bug # TBF, so that abort's cause
- // us to return at each potential yield point.
- return;
- }
- if (++_yielded_workers + finished_workers() == active_workers()) {
- yielding_task()->set_status(YIELDED);
- monitor()->notify_all();
- } else {
- yielding_task()->set_status(YIELDING);
- }
-
- while (true) {
- switch (yielding_task()->status()) {
- case YIELDING:
- case YIELDED: {
- monitor()->wait_without_safepoint_check();
- break; // from switch
- }
- case ACTIVE:
- case ABORTING:
- case COMPLETING: {
- assert(_yielded_workers > 0, "Else why am i here?");
- _yielded_workers--;
- return;
- }
- case INACTIVE:
- case ABORTED:
- case COMPLETED:
- default: {
- ShouldNotReachHere();
- }
- }
- }
- // Only return is from inside switch statement above
- ShouldNotReachHere();
-}
-
-void YieldingFlexibleWorkGang::abort() {
- assert(task() != NULL, "Inconsistency; should have task binding");
- MutexLocker ml(monitor(), Mutex::_no_safepoint_check_flag);
- assert(yielded_workers() < active_workers(), "Consistency check");
- #ifndef PRODUCT
- switch (yielding_task()->status()) {
- // allowed states
- case ACTIVE:
- case ABORTING:
- case COMPLETING:
- case YIELDING:
- break;
- // not allowed states
- case INACTIVE:
- case ABORTED:
- case COMPLETED:
- case YIELDED:
- default:
- ShouldNotReachHere();
- }
- #endif // !PRODUCT
- Status prev_status = yielding_task()->status();
- yielding_task()->set_status(ABORTING);
- if (prev_status == YIELDING) {
- assert(yielded_workers() > 0, "Inconsistency");
- // At least one thread has yielded, wake it up
- // so it can go back to waiting stations ASAP.
- monitor()->notify_all();
- }
-}
-
-///////////////////////////////
-// YieldingFlexibleGangTask
-///////////////////////////////
-void YieldingFlexibleGangTask::yield() {
- assert(gang() != NULL, "No gang to signal");
- gang()->yield();
-}
-
-void YieldingFlexibleGangTask::abort() {
- assert(gang() != NULL, "No gang to signal");
- gang()->abort();
-}
-
-///////////////////////////////
-// YieldingFlexibleGangWorker
-///////////////////////////////
-void YieldingFlexibleGangWorker::loop() {
- int previous_sequence_number = 0;
- Monitor* gang_monitor = yf_gang()->monitor();
- MutexLocker ml(gang_monitor, Mutex::_no_safepoint_check_flag);
- YieldingWorkData data;
- int id;
- while (true) {
- // Check if there is work to do.
- yf_gang()->internal_worker_poll(&data);
- if (data.task() != NULL && data.sequence_number() != previous_sequence_number) {
- // There is work to be done.
- // First check if we need to become active or if there
- // are already the requisite number of workers
- if (yf_gang()->started_workers() == yf_gang()->active_workers()) {
- // There are already enough workers, we do not need to
- // to run; fall through and wait on monitor.
- } else {
- // We need to pitch in and do the work.
- assert(yf_gang()->started_workers() < yf_gang()->active_workers(),
- "Unexpected state");
- id = yf_gang()->started_workers();
- yf_gang()->internal_note_start();
- // Now, release the gang mutex and do the work.
- {
- MutexUnlocker mul(gang_monitor, Mutex::_no_safepoint_check_flag);
- GCIdMark gc_id_mark(data.task()->gc_id());
- data.task()->work(id); // This might include yielding
- }
- // Reacquire monitor and note completion of this worker
- yf_gang()->internal_note_finish();
- // Update status of task based on whether all workers have
- // finished or some have yielded
- assert(data.task() == yf_gang()->task(), "Confused task binding");
- if (yf_gang()->finished_workers() == yf_gang()->active_workers()) {
- switch (data.yf_task()->status()) {
- case ABORTING: {
- data.yf_task()->set_status(ABORTED);
- break;
- }
- case ACTIVE:
- case COMPLETING: {
- data.yf_task()->set_status(COMPLETED);
- break;
- }
- default:
- ShouldNotReachHere();
- }
- gang_monitor->notify_all(); // Notify overseer
- } else { // at least one worker is still working or yielded
- assert(yf_gang()->finished_workers() < yf_gang()->active_workers(),
- "Counts inconsistent");
- switch (data.yf_task()->status()) {
- case ACTIVE: {
- // first, but not only thread to complete
- data.yf_task()->set_status(COMPLETING);
- break;
- }
- case YIELDING: {
- if (yf_gang()->finished_workers() + yf_gang()->yielded_workers()
- == yf_gang()->active_workers()) {
- data.yf_task()->set_status(YIELDED);
- gang_monitor->notify_all(); // notify overseer
- }
- break;
- }
- case ABORTING:
- case COMPLETING: {
- break; // nothing to do
- }
- default: // everything else: INACTIVE, YIELDED, ABORTED, COMPLETED
- ShouldNotReachHere();
- }
- }
- }
- }
- // Remember the sequence number
- previous_sequence_number = data.sequence_number();
- // Wait for more work
- gang_monitor->wait_without_safepoint_check();
- }
-}