jdk

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/*
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 * Copyright (c) 2018, 2022, Red Hat, Inc. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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#include "precompiled.hpp"
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#include "gc/shared/gcArguments.hpp"
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#include "gc/shared/tlab_globals.hpp"
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#include "gc/shared/workerPolicy.hpp"
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#include "gc/shenandoah/shenandoahArguments.hpp"
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#include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
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#include "gc/shenandoah/shenandoahHeap.inline.hpp"
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#include "gc/shenandoah/shenandoahHeapRegion.hpp"
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#include "runtime/globals_extension.hpp"
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#include "runtime/java.hpp"
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#include "utilities/defaultStream.hpp"
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void ShenandoahArguments::initialize() {
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#if !(defined AARCH64 || defined AMD64 || defined IA32 || defined PPC64 || defined RISCV64)
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  vm_exit_during_initialization("Shenandoah GC is not supported on this platform.");
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#endif
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#if 0 // leave this block as stepping stone for future platforms
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  log_warning(gc)("Shenandoah GC is not fully supported on this platform:");
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  log_warning(gc)("  concurrent modes are not supported, only STW cycles are enabled;");
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  log_warning(gc)("  arch-specific barrier code is not implemented, disabling barriers;");
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  FLAG_SET_DEFAULT(ShenandoahGCHeuristics,           "passive");
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  FLAG_SET_DEFAULT(ShenandoahSATBBarrier,            false);
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  FLAG_SET_DEFAULT(ShenandoahLoadRefBarrier,         false);
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  FLAG_SET_DEFAULT(ShenandoahCASBarrier,             false);
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  FLAG_SET_DEFAULT(ShenandoahCloneBarrier,           false);
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  FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers,     false);
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#endif
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  if (UseLargePages) {
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    size_t large_page_size = os::large_page_size();
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    if ((align_up(MaxHeapSize, large_page_size) / large_page_size) < ShenandoahHeapRegion::MIN_NUM_REGIONS) {
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      warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit",
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              os::large_page_size() / K);
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      FLAG_SET_DEFAULT(ShenandoahUncommit, false);
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    }
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  }
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  // Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes
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  // storage allocation code NUMA-aware.
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  if (FLAG_IS_DEFAULT(UseNUMA)) {
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    FLAG_SET_DEFAULT(UseNUMA, true);
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  }
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  // Set up default number of concurrent threads. We want to have cycles complete fast
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  // enough, but we also do not want to steal too much CPU from the concurrently running
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  // application. Using 1/4 of available threads for concurrent GC seems a good
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  // compromise here.
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  bool ergo_conc = FLAG_IS_DEFAULT(ConcGCThreads);
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  if (ergo_conc) {
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    FLAG_SET_DEFAULT(ConcGCThreads, MAX2(1, os::initial_active_processor_count() / 4));
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  }
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  if (ConcGCThreads == 0) {
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    vm_exit_during_initialization("Shenandoah expects ConcGCThreads > 0, check -XX:ConcGCThreads=#");
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  }
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  // Set up default number of parallel threads. We want to have decent pauses performance
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  // which would use parallel threads, but we also do not want to do too many threads
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  // that will overwhelm the OS scheduler. Using 1/2 of available threads seems to be a fair
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  // compromise here. Due to implementation constraints, it should not be lower than
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  // the number of concurrent threads.
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  bool ergo_parallel = FLAG_IS_DEFAULT(ParallelGCThreads);
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  if (ergo_parallel) {
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    FLAG_SET_DEFAULT(ParallelGCThreads, MAX2(1, os::initial_active_processor_count() / 2));
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  }
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  if (ParallelGCThreads == 0) {
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    vm_exit_during_initialization("Shenandoah expects ParallelGCThreads > 0, check -XX:ParallelGCThreads=#");
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  }
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  // Make sure ergonomic decisions do not break the thread count invariants.
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  // This may happen when user overrides one of the flags, but not the other.
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  // When that happens, we want to adjust the setting that was set ergonomically.
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  if (ParallelGCThreads < ConcGCThreads) {
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    if (ergo_conc && !ergo_parallel) {
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      FLAG_SET_DEFAULT(ConcGCThreads, ParallelGCThreads);
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    } else if (!ergo_conc && ergo_parallel) {
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      FLAG_SET_DEFAULT(ParallelGCThreads, ConcGCThreads);
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    } else if (ergo_conc && ergo_parallel) {
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      // Should not happen, check the ergonomic computation above. Fail with relevant error.
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      vm_exit_during_initialization("Shenandoah thread count ergonomic error");
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    } else {
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      // User settings error, report and ask user to rectify.
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      vm_exit_during_initialization("Shenandoah expects ConcGCThreads <= ParallelGCThreads, check -XX:ParallelGCThreads, -XX:ConcGCThreads");
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    }
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  }
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  // Disable support for dynamic number of GC threads. We do not let the runtime
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  // heuristics to misjudge how many threads we need during the heavy concurrent phase
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  // or a GC pause.
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  if (UseDynamicNumberOfGCThreads) {
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    if (FLAG_IS_CMDLINE(UseDynamicNumberOfGCThreads)) {
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      warning("Shenandoah does not support UseDynamicNumberOfGCThreads, disabling");
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    }
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    FLAG_SET_DEFAULT(UseDynamicNumberOfGCThreads, false);
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  }
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  if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
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    // When sampling is enabled, max out the PerfData memory to get more
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    // Shenandoah data in, including Matrix.
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    FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
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  }
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#ifdef COMPILER2
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  // Shenandoah cares more about pause times, rather than raw throughput.
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  if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
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    FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
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    if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
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      FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
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    }
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  }
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#ifdef ASSERT
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  // C2 barrier verification is only reliable when all default barriers are enabled
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  if (ShenandoahVerifyOptoBarriers &&
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          (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier)            ||
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           !FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier)         ||
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           !FLAG_IS_DEFAULT(ShenandoahCASBarrier)             ||
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           !FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
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          )) {
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    warning("Unusual barrier configuration, disabling C2 barrier verification");
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    FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
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  }
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#else
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  guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
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#endif // ASSERT
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#endif // COMPILER2
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  // Record more information about previous cycles for improved debugging pleasure
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  if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
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    FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
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  }
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  if ((InitialHeapSize == MaxHeapSize) && ShenandoahUncommit) {
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    log_info(gc)("Min heap equals to max heap, disabling ShenandoahUncommit");
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    FLAG_SET_DEFAULT(ShenandoahUncommit, false);
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  }
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  // If class unloading is disabled, no unloading for concurrent cycles as well.
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  if (!ClassUnloading) {
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    FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
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  }
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  // TLAB sizing policy makes resizing decisions before each GC cycle. It averages
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  // historical data, assigning more recent data the weight according to TLABAllocationWeight.
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  // Current default is good for generational collectors that run frequent young GCs.
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  // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy
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  // to converge faster over smaller number of resizing decisions.
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  if (FLAG_IS_DEFAULT(TLABAllocationWeight)) {
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    FLAG_SET_DEFAULT(TLABAllocationWeight, 90);
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  }
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}
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size_t ShenandoahArguments::conservative_max_heap_alignment() {
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  size_t align = ShenandoahMaxRegionSize;
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  if (UseLargePages) {
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    align = MAX2(align, os::large_page_size());
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  }
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  return align;
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}
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void ShenandoahArguments::initialize_alignments() {
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  // Need to setup sizes early to get correct alignments.
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  MaxHeapSize = ShenandoahHeapRegion::setup_sizes(MaxHeapSize);
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  // This is expected by our algorithm for ShenandoahHeap::heap_region_containing().
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  size_t align = ShenandoahHeapRegion::region_size_bytes();
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  if (UseLargePages) {
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    align = MAX2(align, os::large_page_size());
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  }
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  SpaceAlignment = align;
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  HeapAlignment = align;
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}
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CollectedHeap* ShenandoahArguments::create_heap() {
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  return new ShenandoahHeap(new ShenandoahCollectorPolicy());
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}
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