1 /*
   2  * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/shared/gcArguments.inline.hpp"
  27 #include "gc/shenandoah/shenandoahArguments.hpp"
  28 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
  29 #include "gc/shenandoah/shenandoahHeap.hpp"
  30 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
  31 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
  32 #include "utilities/defaultStream.hpp"
  33 
  34 void ShenandoahArguments::initialize() {
  35 #if !(defined AARCH64 || defined AMD64 || defined IA32)
  36   vm_exit_during_initialization("Shenandoah GC is not supported on this platform.");
  37 #endif
  38 
  39 #ifdef IA32
  40   log_warning(gc)("Shenandoah GC is not fully supported on this platform:");
  41   log_warning(gc)("  concurrent modes are not supported, only STW cycles are enabled;");
  42   log_warning(gc)("  arch-specific barrier code is not implemented, disabling barriers;");
  43 
  44   FLAG_SET_DEFAULT(ShenandoahGCHeuristics,           "passive");
  45 
  46   FLAG_SET_DEFAULT(ShenandoahSATBBarrier,            false);
  47   FLAG_SET_DEFAULT(ShenandoahKeepAliveBarrier,       false);
  48   FLAG_SET_DEFAULT(ShenandoahWriteBarrier,           false);
  49   FLAG_SET_DEFAULT(ShenandoahReadBarrier,            false);
  50   FLAG_SET_DEFAULT(ShenandoahStoreValEnqueueBarrier, false);
  51   FLAG_SET_DEFAULT(ShenandoahStoreValReadBarrier,    false);
  52   FLAG_SET_DEFAULT(ShenandoahCASBarrier,             false);
  53   FLAG_SET_DEFAULT(ShenandoahAcmpBarrier,            false);
  54   FLAG_SET_DEFAULT(ShenandoahCloneBarrier,           false);
  55 #endif
  56 
  57 #ifdef _LP64
  58   // The optimized ObjArrayChunkedTask takes some bits away from the full 64 addressable
  59   // bits, fail if we ever attempt to address more than we can. Only valid on 64bit.
  60   if (MaxHeapSize >= ObjArrayChunkedTask::max_addressable()) {
  61     jio_fprintf(defaultStream::error_stream(),
  62                 "Shenandoah GC cannot address more than " SIZE_FORMAT " bytes, and " SIZE_FORMAT " bytes heap requested.",
  63                 ObjArrayChunkedTask::max_addressable(), MaxHeapSize);
  64     vm_exit(1);
  65   }
  66 #endif
  67 
  68   if (UseLargePages && (MaxHeapSize / os::large_page_size()) < ShenandoahHeapRegion::MIN_NUM_REGIONS) {
  69     warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit",
  70             os::large_page_size() / K);
  71     FLAG_SET_DEFAULT(ShenandoahUncommit, false);
  72   }
  73 
  74   // Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes
  75   // storage allocation code NUMA-aware, and NUMA interleaving makes the storage
  76   // allocated in consistent manner (interleaving) to minimize run-to-run variance.
  77   if (FLAG_IS_DEFAULT(UseNUMA)) {
  78     FLAG_SET_DEFAULT(UseNUMA, true);
  79     FLAG_SET_DEFAULT(UseNUMAInterleaving, true);
  80   }
  81 
  82   FLAG_SET_DEFAULT(ParallelGCThreads,
  83                    Abstract_VM_Version::parallel_worker_threads());
  84 
  85   if (FLAG_IS_DEFAULT(ConcGCThreads)) {
  86     uint conc_threads = MAX2((uint) 1, ParallelGCThreads);
  87     FLAG_SET_DEFAULT(ConcGCThreads, conc_threads);
  88   }
  89 
  90   if (FLAG_IS_DEFAULT(ParallelRefProcEnabled)) {
  91     FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
  92   }
  93 
  94   if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
  95     // When sampling is enabled, max out the PerfData memory to get more
  96     // Shenandoah data in, including Matrix.
  97     FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
  98   }
  99 
 100 #ifdef COMPILER2
 101   // Shenandoah cares more about pause times, rather than raw throughput.
 102   if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
 103     FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
 104     if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
 105       FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
 106     }
 107   }
 108 #ifdef ASSERT
 109   // C2 barrier verification is only reliable when all default barriers are enabled
 110   if (ShenandoahVerifyOptoBarriers &&
 111           (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier)            ||
 112            !FLAG_IS_DEFAULT(ShenandoahKeepAliveBarrier)       ||
 113            !FLAG_IS_DEFAULT(ShenandoahWriteBarrier)           ||
 114            !FLAG_IS_DEFAULT(ShenandoahReadBarrier)            ||
 115            !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) ||
 116            !FLAG_IS_DEFAULT(ShenandoahStoreValReadBarrier)    ||
 117            !FLAG_IS_DEFAULT(ShenandoahCASBarrier)             ||
 118            !FLAG_IS_DEFAULT(ShenandoahAcmpBarrier)            ||
 119            !FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
 120           )) {
 121     warning("Unusual barrier configuration, disabling C2 barrier verification");
 122     FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
 123   }
 124 #else
 125   guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
 126 #endif // ASSERT
 127 #endif // COMPILER2
 128 
 129   if (AlwaysPreTouch) {
 130     // Shenandoah handles pre-touch on its own. It does not let the
 131     // generic storage code to do the pre-touch before Shenandoah has
 132     // a chance to do it on its own.
 133     FLAG_SET_DEFAULT(AlwaysPreTouch, false);
 134     FLAG_SET_DEFAULT(ShenandoahAlwaysPreTouch, true);
 135   }
 136 
 137   // Shenandoah C2 optimizations apparently dislike the shape of thread-local handshakes.
 138   // Disable it by default, unless we enable it specifically for debugging.
 139   if (FLAG_IS_DEFAULT(ThreadLocalHandshakes)) {
 140     if (ThreadLocalHandshakes) {
 141       FLAG_SET_DEFAULT(ThreadLocalHandshakes, false);
 142     }
 143   } else {
 144     if (ThreadLocalHandshakes) {
 145       warning("Thread-local handshakes are not working correctly with Shenandoah at the moment. Enable at your own risk.");
 146     }
 147   }
 148 
 149   // Record more information about previous cycles for improved debugging pleasure
 150   if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
 151     FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
 152   }
 153 
 154   if (ShenandoahAlwaysPreTouch) {
 155     if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) {
 156       warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit");
 157     }
 158     FLAG_SET_DEFAULT(ShenandoahUncommit, false);
 159   }
 160 
 161   // If class unloading is disabled, no unloading for concurrent cycles as well.
 162   // If class unloading is enabled, users should opt-in for unloading during
 163   // concurrent cycles.
 164   if (!ClassUnloading || !FLAG_IS_CMDLINE(ClassUnloadingWithConcurrentMark)) {
 165     log_info(gc)("Consider -XX:+ClassUnloadingWithConcurrentMark if large pause times "
 166                  "are observed on class-unloading sensitive workloads");
 167     FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
 168   }
 169 
 170   // AOT is not supported yet
 171   if (UseAOT) {
 172     if (!FLAG_IS_DEFAULT(UseAOT)) {
 173       warning("Shenandoah does not support AOT at this moment, disabling UseAOT");
 174     }
 175     FLAG_SET_DEFAULT(UseAOT, false);
 176   }
 177 
 178   // JNI fast get field stuff is not currently supported by Shenandoah.
 179   // It would introduce another heap memory access for reading the forwarding
 180   // pointer, which would have to be guarded by the signal handler machinery.
 181   // See:
 182   // http://mail.openjdk.java.net/pipermail/hotspot-dev/2018-June/032763.html
 183   FLAG_SET_DEFAULT(UseFastJNIAccessors, false);
 184 
 185   // TLAB sizing policy makes resizing decisions before each GC cycle. It averages
 186   // historical data, assigning more recent data the weight according to TLABAllocationWeight.
 187   // Current default is good for generational collectors that run frequent young GCs.
 188   // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy
 189   // to converge faster over smaller number of resizing decisions.
 190   if (FLAG_IS_DEFAULT(TLABAllocationWeight)) {
 191     FLAG_SET_DEFAULT(TLABAllocationWeight, 90);
 192   }
 193 
 194   // Shenandoah needs more C2 nodes to compile some methods with lots of barriers.
 195   // NodeLimitFudgeFactor needs to stay the same relative to MaxNodeLimit.
 196 #ifdef COMPILER2
 197   if (FLAG_IS_DEFAULT(MaxNodeLimit)) {
 198     FLAG_SET_DEFAULT(MaxNodeLimit, MaxNodeLimit * 3);
 199     FLAG_SET_DEFAULT(NodeLimitFudgeFactor, NodeLimitFudgeFactor * 3);
 200   }
 201 #endif
 202 
 203   // Make sure safepoint deadlocks are failing predictably. This sets up VM to report
 204   // fatal error after 10 seconds of wait for safepoint syncronization (not the VM
 205   // operation itself). There is no good reason why Shenandoah would spend that
 206   // much time synchronizing.
 207 #ifdef ASSERT
 208   FLAG_SET_DEFAULT(SafepointTimeout, true);
 209   FLAG_SET_DEFAULT(SafepointTimeoutDelay, 10000);
 210   FLAG_SET_DEFAULT(AbortVMOnSafepointTimeout, true);
 211 #endif
 212 }
 213 
 214 size_t ShenandoahArguments::conservative_max_heap_alignment() {
 215   size_t align = ShenandoahMaxRegionSize;
 216   if (UseLargePages) {
 217     align = MAX2(align, os::large_page_size());
 218   }
 219   return align;
 220 }
 221 
 222 CollectedHeap* ShenandoahArguments::create_heap() {
 223   return create_heap_with_policy<ShenandoahHeap, ShenandoahCollectorPolicy>();
 224 }