| /* | |
| * Copyright (c) 2018, 2025, 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 "gc/shared/collectedHeap.hpp" | |
| #include "gc/shared/workerPolicy.hpp" | |
| #include "logging/log.hpp" | |
| #include "memory/universe.hpp" | |
| #include "runtime/globals_extension.hpp" | |
| #include "runtime/os.hpp" | |
| #include "runtime/vm_version.hpp" | |
| uint WorkerPolicy::_parallel_worker_threads = 0; | |
| bool WorkerPolicy::_parallel_worker_threads_initialized = false; | |
| uint WorkerPolicy::nof_parallel_worker_threads(uint num, | |
| uint den, | |
| uint switch_pt) { | |
| if (FLAG_IS_DEFAULT(ParallelGCThreads)) { | |
| assert(ParallelGCThreads == 0, "Default ParallelGCThreads is not 0"); | |
| uint threads; | |
| // For very large machines, there are diminishing returns | |
| // for large numbers of worker threads. Instead of | |
| // hogging the whole system, use a fraction of the workers for every | |
| // processor after the first 8. For example, on a 72 cpu machine | |
| // and a chosen fraction of 5/8 | |
| // use 8 + (72 - 8) * (5/8) == 48 worker threads. | |
| uint ncpus = (uint) os::initial_active_processor_count(); | |
| threads = (ncpus <= switch_pt) ? | |
| ncpus : | |
| (switch_pt + ((ncpus - switch_pt) * num) / den); | |
| #ifndef _LP64 | |
| // On 32-bit binaries the virtual address space available to the JVM | |
| // is usually limited to 2-3 GB (depends on the platform). | |
| // Do not use up address space with too many threads (stacks and per-thread | |
| // data). Note that x86 apps running on Win64 have 2 stacks per thread. | |
| // GC may more generally scale down threads by max heap size (etc), but the | |
| // consequences of over-provisioning threads are higher on 32-bit JVMS, | |
| // so add hard limit here: | |
| threads = MIN2(threads, (2 * switch_pt)); | |
| #endif | |
| return threads; | |
| } else { | |
| return ParallelGCThreads; | |
| } | |
| } | |
| uint WorkerPolicy::calc_parallel_worker_threads() { | |
| uint den = VM_Version::parallel_worker_threads_denominator(); | |
| return nof_parallel_worker_threads(5, den, 8); | |
| } | |
| uint WorkerPolicy::parallel_worker_threads() { | |
| if (!_parallel_worker_threads_initialized) { | |
| _parallel_worker_threads = WorkerPolicy::calc_parallel_worker_threads(); | |
| _parallel_worker_threads_initialized = true; | |
| } | |
| return _parallel_worker_threads; | |
| } | |
| // If the number of GC threads was set on the command line, use it. | |
| // Else | |
| // Calculate the number of GC threads based on the number of Java threads. | |
| // Calculate the number of GC threads based on the size of the heap. | |
| // Use the larger. | |
| uint WorkerPolicy::calc_default_active_workers(uintx total_workers, | |
| const uintx min_workers, | |
| uintx active_workers, | |
| uintx application_workers) { | |
| // If the user has specifically set the number of GC threads, use them. | |
| // If the user has turned off using a dynamic number of GC threads | |
| // or the users has requested a specific number, set the active | |
| // number of workers to all the workers. | |
| uintx new_active_workers = total_workers; | |
| uintx prev_active_workers = active_workers; | |
| uintx active_workers_by_JT = 0; | |
| uintx active_workers_by_heap_size = 0; | |
| // Always use at least min_workers but use up to | |
| // GCThreadsPerJavaThreads * application threads. | |
| active_workers_by_JT = | |
| MAX2((uintx) GCWorkersPerJavaThread * application_workers, | |
| min_workers); | |
| // Choose a number of GC threads based on the current size | |
| // of the heap. This may be complicated because the size of | |
| // the heap depends on factors such as the throughput goal. | |
| // Still a large heap should be collected by more GC threads. | |
| active_workers_by_heap_size = | |
| MAX2((size_t) 2U, Universe::heap()->capacity() / HeapSizePerGCThread); | |
| uintx max_active_workers = | |
| MAX2(active_workers_by_JT, active_workers_by_heap_size); | |
| new_active_workers = MIN2(max_active_workers, (uintx) total_workers); | |
| // Increase GC workers instantly but decrease them more | |
| // slowly. | |
| if (new_active_workers < prev_active_workers) { | |
| new_active_workers = | |
| MAX2(min_workers, (prev_active_workers + new_active_workers) / 2); | |
| } | |
| // Check once more that the number of workers is within the limits. | |
| assert(min_workers <= total_workers, "Minimum workers not consistent with total workers"); | |
| assert(new_active_workers >= min_workers, "Minimum workers not observed"); | |
| assert(new_active_workers <= total_workers, "Total workers not observed"); | |
| log_trace(gc, task)("WorkerPolicy::calc_default_active_workers() : " | |
| "active_workers(): %zu new_active_workers: %zu " | |
| "prev_active_workers: %zu\n" | |
| " active_workers_by_JT: %zu active_workers_by_heap_size: %zu", | |
| active_workers, new_active_workers, prev_active_workers, | |
| active_workers_by_JT, active_workers_by_heap_size); | |
| assert(new_active_workers > 0, "Always need at least 1"); | |
| return new_active_workers; | |
| } | |
| uint WorkerPolicy::calc_active_workers(uintx total_workers, | |
| uintx active_workers, | |
| uintx application_workers) { | |
| // If the user has specifically set the number of GC threads, use them. | |
| // If the user has turned off using a dynamic number of GC threads | |
| // or the users has requested a specific number, set the active | |
| // number of workers to all the workers. | |
| uint new_active_workers; | |
| if (!UseDynamicNumberOfGCThreads || !FLAG_IS_DEFAULT(ParallelGCThreads)) { | |
| new_active_workers = total_workers; | |
| } else { | |
| uintx min_workers = (total_workers == 1) ? 1 : 2; | |
| new_active_workers = calc_default_active_workers(total_workers, | |
| min_workers, | |
| active_workers, | |
| application_workers); | |
| } | |
| assert(new_active_workers > 0, "Always need at least 1"); | |
| return new_active_workers; | |
| } | |
| uint WorkerPolicy::calc_active_conc_workers(uintx total_workers, | |
| uintx active_workers, | |
| uintx application_workers) { | |
| if (!UseDynamicNumberOfGCThreads || !FLAG_IS_DEFAULT(ConcGCThreads)) { | |
| return ConcGCThreads; | |
| } else { | |
| uint no_of_gc_threads = calc_default_active_workers(total_workers, | |
| 1, /* Minimum number of workers */ | |
| active_workers, | |
| application_workers); | |
| return no_of_gc_threads; | |
| } | |
| } |