/*

 * 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.hpp"

#include "gc/shared/workerPolicy.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);

  }

  // 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;

}

void ShenandoahArguments::initialize_alignments() {

  // Need to setup sizes early to get correct alignments.

  ShenandoahHeapRegion::setup_sizes(MaxHeapSize);

  // This is expected by our algorithm for ShenandoahHeap::heap_region_containing().

  size_t align = ShenandoahHeapRegion::region_size_bytes();

  if (UseLargePages) {

    align = MAX2(align, os::large_page_size());

  }

  SpaceAlignment = align;

  HeapAlignment = align;

}

CollectedHeap* ShenandoahArguments::create_heap() {

  return new ShenandoahHeap(new ShenandoahCollectorPolicy());

}