--- /dev/null 2020-01-17 11:46:19.065201212 +0100 +++ new/src/hotspot/share/gc/shenandoah/shenandoahArguments.cpp 2020-01-17 17:09:49.263131628 +0100 @@ -0,0 +1,240 @@ +/* + * Copyright (c) 2018, 2019, Red Hat, Inc. 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/shared/gcArguments.inline.hpp" +#include "gc/shenandoah/shenandoahArguments.hpp" +#include "gc/shenandoah/shenandoahCollectorPolicy.hpp" +#include "gc/shenandoah/shenandoahHeap.inline.hpp" +#include "gc/shenandoah/shenandoahHeapRegion.hpp" +#include "utilities/defaultStream.hpp" + +void ShenandoahArguments::initialize() { +#if !(defined AARCH64 || defined AMD64 || defined IA32) + vm_exit_during_initialization("Shenandoah GC is not supported on this platform."); +#endif + +#if 0 // leave this block as stepping stone for future platforms + log_warning(gc)("Shenandoah GC is not fully supported on this platform:"); + log_warning(gc)(" concurrent modes are not supported, only STW cycles are enabled;"); + log_warning(gc)(" arch-specific barrier code is not implemented, disabling barriers;"); + + FLAG_SET_DEFAULT(ShenandoahGCHeuristics, "passive"); + + FLAG_SET_DEFAULT(ShenandoahSATBBarrier, false); + FLAG_SET_DEFAULT(ShenandoahLoadRefBarrier, false); + FLAG_SET_DEFAULT(ShenandoahKeepAliveBarrier, false); + FLAG_SET_DEFAULT(ShenandoahStoreValEnqueueBarrier, false); + FLAG_SET_DEFAULT(ShenandoahCASBarrier, false); + FLAG_SET_DEFAULT(ShenandoahCloneBarrier, false); + + FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false); +#endif + + if (UseLargePages && (MaxHeapSize / os::large_page_size()) < ShenandoahHeapRegion::MIN_NUM_REGIONS) { + warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit", + os::large_page_size() / K); + FLAG_SET_DEFAULT(ShenandoahUncommit, false); + } + + // Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes + // storage allocation code NUMA-aware. + if (FLAG_IS_DEFAULT(UseNUMA)) { + FLAG_SET_DEFAULT(UseNUMA, true); + } + + // Set up default number of concurrent threads. We want to have cycles complete fast + // enough, but we also do not want to steal too much CPU from the concurrently running + // application. Using 1/4 of available threads for concurrent GC seems a good + // compromise here. + bool ergo_conc = FLAG_IS_DEFAULT(ConcGCThreads); + if (ergo_conc) { + FLAG_SET_DEFAULT(ConcGCThreads, MAX2(1, os::processor_count() / 4)); + } + + if (ConcGCThreads == 0) { + vm_exit_during_initialization("Shenandoah expects ConcGCThreads > 0, check -XX:ConcGCThreads=#"); + } + + // Set up default number of parallel threads. We want to have decent pauses performance + // which would use parallel threads, but we also do not want to do too many threads + // that will overwhelm the OS scheduler. Using 1/2 of available threads seems to be a fair + // compromise here. Due to implementation constraints, it should not be lower than + // the number of concurrent threads. + bool ergo_parallel = FLAG_IS_DEFAULT(ParallelGCThreads); + if (ergo_parallel) { + FLAG_SET_DEFAULT(ParallelGCThreads, MAX2(1, os::processor_count() / 2)); + } + + if (ParallelGCThreads == 0) { + vm_exit_during_initialization("Shenandoah expects ParallelGCThreads > 0, check -XX:ParallelGCThreads=#"); + } + + // Make sure ergonomic decisions do not break the thread count invariants. + // This may happen when user overrides one of the flags, but not the other. + // When that happens, we want to adjust the setting that was set ergonomically. + if (ParallelGCThreads < ConcGCThreads) { + if (ergo_conc && !ergo_parallel) { + FLAG_SET_DEFAULT(ConcGCThreads, ParallelGCThreads); + } else if (!ergo_conc && ergo_parallel) { + FLAG_SET_DEFAULT(ParallelGCThreads, ConcGCThreads); + } else if (ergo_conc && ergo_parallel) { + // Should not happen, check the ergonomic computation above. Fail with relevant error. + vm_exit_during_initialization("Shenandoah thread count ergonomic error"); + } else { + // User settings error, report and ask user to rectify. + vm_exit_during_initialization("Shenandoah expects ConcGCThreads <= ParallelGCThreads, check -XX:ParallelGCThreads, -XX:ConcGCThreads"); + } + } + + if (FLAG_IS_DEFAULT(ParallelRefProcEnabled)) { + FLAG_SET_DEFAULT(ParallelRefProcEnabled, true); + } + + if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) { + // When sampling is enabled, max out the PerfData memory to get more + // Shenandoah data in, including Matrix. + FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K); + } + +#ifdef COMPILER2 + // Shenandoah cares more about pause times, rather than raw throughput. + if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) { + FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true); + if (FLAG_IS_DEFAULT(LoopStripMiningIter)) { + FLAG_SET_DEFAULT(LoopStripMiningIter, 1000); + } + } +#ifdef ASSERT + // C2 barrier verification is only reliable when all default barriers are enabled + if (ShenandoahVerifyOptoBarriers && + (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) || + !FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier) || + !FLAG_IS_DEFAULT(ShenandoahKeepAliveBarrier) || + !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) || + !FLAG_IS_DEFAULT(ShenandoahCASBarrier) || + !FLAG_IS_DEFAULT(ShenandoahCloneBarrier) + )) { + warning("Unusual barrier configuration, disabling C2 barrier verification"); + FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false); + } +#else + guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled"); +#endif // ASSERT +#endif // COMPILER2 + + if (AlwaysPreTouch) { + // Shenandoah handles pre-touch on its own. It does not let the + // generic storage code to do the pre-touch before Shenandoah has + // a chance to do it on its own. + FLAG_SET_DEFAULT(AlwaysPreTouch, false); + FLAG_SET_DEFAULT(ShenandoahAlwaysPreTouch, true); + } + + // Shenandoah C2 optimizations apparently dislike the shape of thread-local handshakes. + // Disable it by default, unless we enable it specifically for debugging. + if (FLAG_IS_DEFAULT(ThreadLocalHandshakes)) { + if (ThreadLocalHandshakes) { + FLAG_SET_DEFAULT(ThreadLocalHandshakes, false); + } + } else { + if (ThreadLocalHandshakes) { + warning("Thread-local handshakes are not working correctly with Shenandoah at the moment. Enable at your own risk."); + } + } + + // Record more information about previous cycles for improved debugging pleasure + if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) { + FLAG_SET_DEFAULT(LogEventsBufferEntries, 250); + } + + if (ShenandoahAlwaysPreTouch) { + if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) { + warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit"); + } + FLAG_SET_DEFAULT(ShenandoahUncommit, false); + } + + if ((InitialHeapSize == MaxHeapSize) && ShenandoahUncommit) { + log_info(gc)("Min heap equals to max heap, disabling ShenandoahUncommit"); + FLAG_SET_DEFAULT(ShenandoahUncommit, false); + } + + // If class unloading is disabled, no unloading for concurrent cycles as well. + // If class unloading is enabled, users should opt-in for unloading during + // concurrent cycles. + if (!ClassUnloading || !FLAG_IS_CMDLINE(ClassUnloadingWithConcurrentMark)) { + log_info(gc)("Consider -XX:+ClassUnloadingWithConcurrentMark if large pause times " + "are observed on class-unloading sensitive workloads"); + FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false); + } + + // AOT is not supported yet + if (UseAOT) { + if (!FLAG_IS_DEFAULT(UseAOT)) { + warning("Shenandoah does not support AOT at this moment, disabling UseAOT"); + } + FLAG_SET_DEFAULT(UseAOT, false); + } + + // TLAB sizing policy makes resizing decisions before each GC cycle. It averages + // historical data, assigning more recent data the weight according to TLABAllocationWeight. + // Current default is good for generational collectors that run frequent young GCs. + // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy + // to converge faster over smaller number of resizing decisions. + if (FLAG_IS_DEFAULT(TLABAllocationWeight)) { + FLAG_SET_DEFAULT(TLABAllocationWeight, 90); + } + + // Shenandoah needs more C2 nodes to compile some methods with lots of barriers. + // NodeLimitFudgeFactor needs to stay the same relative to MaxNodeLimit. +#ifdef COMPILER2 + if (FLAG_IS_DEFAULT(MaxNodeLimit)) { + FLAG_SET_DEFAULT(MaxNodeLimit, MaxNodeLimit * 3); + FLAG_SET_DEFAULT(NodeLimitFudgeFactor, NodeLimitFudgeFactor * 3); + } +#endif + + // Make sure safepoint deadlocks are failing predictably. This sets up VM to report + // fatal error after 10 seconds of wait for safepoint syncronization (not the VM + // operation itself). There is no good reason why Shenandoah would spend that + // much time synchronizing. +#ifdef ASSERT + FLAG_SET_DEFAULT(SafepointTimeout, true); + FLAG_SET_DEFAULT(SafepointTimeoutDelay, 10000); + FLAG_SET_DEFAULT(AbortVMOnSafepointTimeout, true); +#endif +} + +size_t ShenandoahArguments::conservative_max_heap_alignment() { + size_t align = ShenandoahMaxRegionSize; + if (UseLargePages) { + align = MAX2(align, os::large_page_size()); + } + return align; +} + +CollectedHeap* ShenandoahArguments::create_heap() { + return create_heap_with_policy(); +}