1 /*
   2  * Copyright (c) 2018, 2019, 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.hpp"
  27 #include "gc/shared/workerPolicy.hpp"
  28 #include "gc/shenandoah/shenandoahArguments.hpp"
  29 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
  30 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  31 #include "gc/shenandoah/shenandoahHeapRegion.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 #if 0 // leave this block as stepping stone for future platforms
  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(ShenandoahLoadRefBarrier,         false);
  48   FLAG_SET_DEFAULT(ShenandoahKeepAliveBarrier,       false);
  49   FLAG_SET_DEFAULT(ShenandoahStoreValEnqueueBarrier, false);
  50   FLAG_SET_DEFAULT(ShenandoahCASBarrier,             false);
  51   FLAG_SET_DEFAULT(ShenandoahCloneBarrier,           false);
  52 
  53   FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers,     false);
  54 #endif
  55 
  56   if (UseLargePages && (MaxHeapSize / os::large_page_size()) < ShenandoahHeapRegion::MIN_NUM_REGIONS) {
  57     warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit",
  58             os::large_page_size() / K);
  59     FLAG_SET_DEFAULT(ShenandoahUncommit, false);
  60   }
  61 
  62   // Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes
  63   // storage allocation code NUMA-aware.
  64   if (FLAG_IS_DEFAULT(UseNUMA)) {
  65     FLAG_SET_DEFAULT(UseNUMA, true);
  66   }
  67 
  68   // Set up default number of concurrent threads. We want to have cycles complete fast
  69   // enough, but we also do not want to steal too much CPU from the concurrently running
  70   // application. Using 1/4 of available threads for concurrent GC seems a good
  71   // compromise here.
  72   bool ergo_conc = FLAG_IS_DEFAULT(ConcGCThreads);
  73   if (ergo_conc) {
  74     FLAG_SET_DEFAULT(ConcGCThreads, MAX2(1, os::processor_count() / 4));
  75   }
  76 
  77   if (ConcGCThreads == 0) {
  78     vm_exit_during_initialization("Shenandoah expects ConcGCThreads > 0, check -XX:ConcGCThreads=#");
  79   }
  80 
  81   // Set up default number of parallel threads. We want to have decent pauses performance
  82   // which would use parallel threads, but we also do not want to do too many threads
  83   // that will overwhelm the OS scheduler. Using 1/2 of available threads seems to be a fair
  84   // compromise here. Due to implementation constraints, it should not be lower than
  85   // the number of concurrent threads.
  86   bool ergo_parallel = FLAG_IS_DEFAULT(ParallelGCThreads);
  87   if (ergo_parallel) {
  88     FLAG_SET_DEFAULT(ParallelGCThreads, MAX2(1, os::processor_count() / 2));
  89   }
  90 
  91   if (ParallelGCThreads == 0) {
  92     vm_exit_during_initialization("Shenandoah expects ParallelGCThreads > 0, check -XX:ParallelGCThreads=#");
  93   }
  94 
  95   // Make sure ergonomic decisions do not break the thread count invariants.
  96   // This may happen when user overrides one of the flags, but not the other.
  97   // When that happens, we want to adjust the setting that was set ergonomically.
  98   if (ParallelGCThreads < ConcGCThreads) {
  99     if (ergo_conc && !ergo_parallel) {
 100       FLAG_SET_DEFAULT(ConcGCThreads, ParallelGCThreads);
 101     } else if (!ergo_conc && ergo_parallel) {
 102       FLAG_SET_DEFAULT(ParallelGCThreads, ConcGCThreads);
 103     } else if (ergo_conc && ergo_parallel) {
 104       // Should not happen, check the ergonomic computation above. Fail with relevant error.
 105       vm_exit_during_initialization("Shenandoah thread count ergonomic error");
 106     } else {
 107       // User settings error, report and ask user to rectify.
 108       vm_exit_during_initialization("Shenandoah expects ConcGCThreads <= ParallelGCThreads, check -XX:ParallelGCThreads, -XX:ConcGCThreads");
 109     }
 110   }
 111 
 112   if (FLAG_IS_DEFAULT(ParallelRefProcEnabled)) {
 113     FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
 114   }
 115 
 116   if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
 117     // When sampling is enabled, max out the PerfData memory to get more
 118     // Shenandoah data in, including Matrix.
 119     FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
 120   }
 121 
 122 #ifdef COMPILER2
 123   // Shenandoah cares more about pause times, rather than raw throughput.
 124   if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
 125     FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
 126     if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
 127       FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
 128     }
 129   }
 130 #ifdef ASSERT
 131   // C2 barrier verification is only reliable when all default barriers are enabled
 132   if (ShenandoahVerifyOptoBarriers &&
 133           (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier)            ||
 134            !FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier)         ||
 135            !FLAG_IS_DEFAULT(ShenandoahKeepAliveBarrier)       ||
 136            !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) ||
 137            !FLAG_IS_DEFAULT(ShenandoahCASBarrier)             ||
 138            !FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
 139           )) {
 140     warning("Unusual barrier configuration, disabling C2 barrier verification");
 141     FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
 142   }
 143 #else
 144   guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
 145 #endif // ASSERT
 146 #endif // COMPILER2
 147 
 148   if (AlwaysPreTouch) {
 149     // Shenandoah handles pre-touch on its own. It does not let the
 150     // generic storage code to do the pre-touch before Shenandoah has
 151     // a chance to do it on its own.
 152     FLAG_SET_DEFAULT(AlwaysPreTouch, false);
 153     FLAG_SET_DEFAULT(ShenandoahAlwaysPreTouch, true);
 154   }
 155 
 156   // Record more information about previous cycles for improved debugging pleasure
 157   if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
 158     FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
 159   }
 160 
 161   if (ShenandoahAlwaysPreTouch) {
 162     if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) {
 163       warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit");
 164     }
 165     FLAG_SET_DEFAULT(ShenandoahUncommit, false);
 166   }
 167 
 168   if ((InitialHeapSize == MaxHeapSize) && ShenandoahUncommit) {
 169     log_info(gc)("Min heap equals to max heap, disabling ShenandoahUncommit");
 170     FLAG_SET_DEFAULT(ShenandoahUncommit, false);
 171   }
 172 
 173   // If class unloading is disabled, no unloading for concurrent cycles as well.
 174   if (!ClassUnloading) {
 175     FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
 176   }
 177 
 178   // AOT is not supported yet
 179   if (UseAOT) {
 180     if (!FLAG_IS_DEFAULT(UseAOT)) {
 181       warning("Shenandoah does not support AOT at this moment, disabling UseAOT");
 182     }
 183     FLAG_SET_DEFAULT(UseAOT, false);
 184   }
 185 
 186   // TLAB sizing policy makes resizing decisions before each GC cycle. It averages
 187   // historical data, assigning more recent data the weight according to TLABAllocationWeight.
 188   // Current default is good for generational collectors that run frequent young GCs.
 189   // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy
 190   // to converge faster over smaller number of resizing decisions.
 191   if (FLAG_IS_DEFAULT(TLABAllocationWeight)) {
 192     FLAG_SET_DEFAULT(TLABAllocationWeight, 90);
 193   }
 194 
 195   // Shenandoah needs more C2 nodes to compile some methods with lots of barriers.
 196   // NodeLimitFudgeFactor needs to stay the same relative to MaxNodeLimit.
 197 #ifdef COMPILER2
 198   if (FLAG_IS_DEFAULT(MaxNodeLimit)) {
 199     FLAG_SET_DEFAULT(MaxNodeLimit, MaxNodeLimit * 3);
 200     FLAG_SET_DEFAULT(NodeLimitFudgeFactor, NodeLimitFudgeFactor * 3);
 201   }
 202 #endif
 203 
 204   // Make sure safepoint deadlocks are failing predictably. This sets up VM to report
 205   // fatal error after 10 seconds of wait for safepoint syncronization (not the VM
 206   // operation itself). There is no good reason why Shenandoah would spend that
 207   // much time synchronizing.
 208 #ifdef ASSERT
 209   FLAG_SET_DEFAULT(SafepointTimeout, true);
 210   FLAG_SET_DEFAULT(SafepointTimeoutDelay, 10000);
 211   FLAG_SET_DEFAULT(AbortVMOnSafepointTimeout, true);
 212 #endif
 213 }
 214 
 215 size_t ShenandoahArguments::conservative_max_heap_alignment() {
 216   size_t align = ShenandoahMaxRegionSize;
 217   if (UseLargePages) {
 218     align = MAX2(align, os::large_page_size());
 219   }
 220   return align;
 221 }
 222 
 223 void ShenandoahArguments::initialize_alignments() {
 224   // Need to setup sizes early to get correct alignments.
 225   ShenandoahHeapRegion::setup_sizes(MaxHeapSize);
 226 
 227   // This is expected by our algorithm for ShenandoahHeap::heap_region_containing().
 228   size_t align = ShenandoahHeapRegion::region_size_bytes();
 229   if (UseLargePages) {
 230     align = MAX2(align, os::large_page_size());
 231   }
 232   SpaceAlignment = align;
 233   HeapAlignment = align;
 234 }
 235 
 236 CollectedHeap* ShenandoahArguments::create_heap() {
 237   return new ShenandoahHeap(new ShenandoahCollectorPolicy());
 238 }