1 /* 2 * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved. 3 * Copyright (c) 2016, 2020, Red Hat, Inc. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 * 24 */ 25 26 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP 27 #define SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP 28 29 #include "utilities/macros.hpp" 30 #if INCLUDE_SHENANDOAHGC 31 #include "runtime/flags/jvmFlag.hpp" 32 PRODUCT_FLAG(size_t, ShenandoahRegionSize, 0, JVMFlag::EXPERIMENTAL, 33 "Static heap region size. Set zero to enable automatic sizing."); 34 35 PRODUCT_FLAG(size_t, ShenandoahTargetNumRegions, 2048, JVMFlag::EXPERIMENTAL, 36 "With automatic region sizing, this is the approximate number " 37 "of regions that would be used, within min/max region size " 38 "limits."); 39 40 PRODUCT_FLAG(size_t, ShenandoahMinRegionSize, 256 * K, JVMFlag::EXPERIMENTAL, 41 "With automatic region sizing, the regions would be at least " 42 "this large."); 43 44 PRODUCT_FLAG(size_t, ShenandoahMaxRegionSize, 32 * M, JVMFlag::EXPERIMENTAL, 45 "With automatic region sizing, the regions would be at most " 46 "this large."); 47 48 PRODUCT_FLAG(intx, ShenandoahHumongousThreshold, 100, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 49 "Humongous objects are allocated in separate regions. " 50 "This setting defines how large the object should be to be " 51 "deemed humongous. Value is in percents of heap region size. " 52 "This also caps the maximum TLAB size."); 53 FLAG_RANGE( ShenandoahHumongousThreshold, 1, 100); 54 55 PRODUCT_FLAG(ccstr, ShenandoahGCMode, "normal", JVMFlag::EXPERIMENTAL, 56 "GC mode to use. Among other things, this defines which " 57 "barriers are in in use. Possible values are:" 58 " normal - default concurrent GC (three pass mark-evac-update);" 59 " passive - stop the world GC only (either degenerated or full)"); 60 61 PRODUCT_FLAG(ccstr, ShenandoahGCHeuristics, "adaptive", JVMFlag::EXPERIMENTAL, 62 "GC heuristics to use. This fine-tunes the GC mode selected, " 63 "by choosing when to start the GC, how much to process on each " 64 "cycle, and what other features to automatically enable. " 65 "Possible values are:" 66 " adaptive - adapt to maintain the given amount of free heap " 67 "at all times, even during the GC cycle;" 68 " static - trigger GC when free heap falls below the threshold;" 69 " aggressive - run GC continuously, try to evacuate everything;" 70 " compact - run GC more frequently and with deeper targets to " 71 "free up more memory."); 72 73 PRODUCT_FLAG(uintx, ShenandoahRefProcFrequency, 5, JVMFlag::EXPERIMENTAL, 74 "Process process weak (soft, phantom, finalizers) references " 75 "every Nth cycle. Normally affects concurrent GC cycles only, " 76 "as degenerated and full GCs would try to process references " 77 "regardless. Set to zero to disable reference processing " 78 "completely."); 79 80 PRODUCT_FLAG(uintx, ShenandoahUnloadClassesFrequency, 1, JVMFlag::EXPERIMENTAL, 81 "Unload the classes every Nth cycle. Normally affects concurrent " 82 "GC cycles, as degenerated and full GCs would try to unload " 83 "classes regardless. Set to zero to disable class unloading."); 84 85 PRODUCT_FLAG(uintx, ShenandoahGarbageThreshold, 25, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 86 "How much garbage a region has to contain before it would be " 87 "taken for collection. This a guideline only, as GC heuristics " 88 "may select the region for collection even if it has little " 89 "garbage. This also affects how much internal fragmentation the " 90 "collector accepts. In percents of heap region size."); 91 FLAG_RANGE( ShenandoahGarbageThreshold, 0,100); 92 93 PRODUCT_FLAG(uintx, ShenandoahInitFreeThreshold, 70, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 94 "How much heap should be free before some heuristics trigger the " 95 "initial (learning) cycles. Affects cycle frequency on startup " 96 "and after drastic state changes, e.g. after degenerated/full " 97 "GC cycles. In percents of total heap size."); 98 FLAG_RANGE( ShenandoahInitFreeThreshold, 0,100); 99 100 PRODUCT_FLAG(uintx, ShenandoahMinFreeThreshold, 10, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 101 "How much heap should be free before most heuristics trigger the " 102 "collection, even without other triggers. Provides the safety " 103 "margin for many heuristics. In percents of total heap size."); 104 FLAG_RANGE( ShenandoahMinFreeThreshold, 0,100); 105 106 PRODUCT_FLAG(uintx, ShenandoahAllocationThreshold, 0, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 107 "How many new allocations should happen since the last GC cycle " 108 "before some heuristics trigger the collection. In percents of " 109 "total heap size. Set to zero to effectively disable."); 110 FLAG_RANGE( ShenandoahAllocationThreshold, 0,100); 111 112 PRODUCT_FLAG(uintx, ShenandoahAllocSpikeFactor, 5, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 113 "How much of heap should some heuristics reserve for absorbing " 114 "the allocation spikes. Larger value wastes more memory in " 115 "non-emergency cases, but provides more safety in emergency " 116 "cases. In percents of total heap size."); 117 FLAG_RANGE( ShenandoahAllocSpikeFactor, 0,100); 118 119 PRODUCT_FLAG(uintx, ShenandoahLearningSteps, 5, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 120 "The number of cycles some heuristics take to collect in order " 121 "to learn application and GC performance."); 122 FLAG_RANGE( ShenandoahLearningSteps, 0,100); 123 124 PRODUCT_FLAG(uintx, ShenandoahImmediateThreshold, 90, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 125 "The cycle may shortcut when enough garbage can be reclaimed " 126 "from the immediate garbage (completely garbage regions). " 127 "In percents of total garbage found. Setting this threshold " 128 "to 100 effectively disables the shortcut."); 129 FLAG_RANGE( ShenandoahImmediateThreshold, 0,100); 130 131 PRODUCT_FLAG(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, JVMFlag::EXPERIMENTAL, 132 "Many heuristics would guarantee a concurrent GC cycle at " 133 "least with this interval. This is useful when large idle " 134 "intervals are present, where GC can run without stealing " 135 "time from active application. Time is in milliseconds. " 136 "Setting this to 0 disables the feature."); 137 138 PRODUCT_FLAG(bool, ShenandoahAlwaysClearSoftRefs, false, JVMFlag::EXPERIMENTAL, 139 "Unconditionally clear soft references, instead of using any " 140 "other cleanup policy. This minimizes footprint at expense of" 141 "more soft reference churn in applications."); 142 143 PRODUCT_FLAG(bool, ShenandoahUncommit, true, JVMFlag::EXPERIMENTAL, 144 "Allow to uncommit memory under unused regions and metadata. " 145 "This optimizes footprint at expense of allocation latency in " 146 "regions that require committing back. Uncommits would be " 147 "disabled by some heuristics, or with static heap size."); 148 149 PRODUCT_FLAG(uintx, ShenandoahUncommitDelay, 5*60*1000, JVMFlag::EXPERIMENTAL, 150 "Uncommit memory for regions that were not used for more than " 151 "this time. First use after that would incur allocation stalls. " 152 "Actively used regions would never be uncommitted, because they " 153 "do not become unused longer than this delay. Time is in " 154 "milliseconds. Setting this delay to 0 effectively uncommits " 155 "regions almost immediately after they become unused."); 156 157 PRODUCT_FLAG(bool, ShenandoahRegionSampling, false, JVMFlag::EXPERIMENTAL, 158 "Provide heap region sampling data via jvmstat."); 159 160 PRODUCT_FLAG(int, ShenandoahRegionSamplingRate, 40, JVMFlag::EXPERIMENTAL, 161 "Sampling rate for heap region sampling. In milliseconds between " 162 "the samples. Higher values provide more fidelity, at expense " 163 "of more sampling overhead."); 164 165 PRODUCT_FLAG(uintx, ShenandoahControlIntervalMin, 1, JVMFlag::EXPERIMENTAL, 166 "The minimum sleep interval for the control loop that drives " 167 "the cycles. Lower values would increase GC responsiveness " 168 "to changing heap conditions, at the expense of higher perf " 169 "overhead. Time is in milliseconds."); 170 171 PRODUCT_FLAG(uintx, ShenandoahControlIntervalMax, 10, JVMFlag::EXPERIMENTAL, 172 "The maximum sleep interval for control loop that drives " 173 "the cycles. Lower values would increase GC responsiveness " 174 "to changing heap conditions, at the expense of higher perf " 175 "overhead. Time is in milliseconds."); 176 177 PRODUCT_FLAG(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, JVMFlag::EXPERIMENTAL, 178 "The time period for one step in control loop interval " 179 "adjustment. Lower values make adjustments faster, at the " 180 "expense of higher perf overhead. Time is in milliseconds."); 181 182 PRODUCT_FLAG(bool, ShenandoahCriticalControlThreadPriority, false, JVMFlag::EXPERIMENTAL, 183 "Run control thread runs at critical scheduling priority."); 184 185 PRODUCT_FLAG(bool, ShenandoahVerify, false, JVMFlag::DIAGNOSTIC, 186 "Enable internal verification. This would catch many GC bugs, " 187 "but it would also stall the collector during the verification, " 188 "which prolongs the pauses and might hide other bugs."); 189 190 PRODUCT_FLAG(intx, ShenandoahVerifyLevel, 4, JVMFlag::DIAGNOSTIC, 191 "Verification level, higher levels check more, taking more time. " 192 "Accepted values are:" 193 " 0 = basic heap checks; " 194 " 1 = previous level, plus basic region checks; " 195 " 2 = previous level, plus all roots; " 196 " 3 = previous level, plus all reachable objects; " 197 " 4 = previous level, plus all marked objects"); 198 199 PRODUCT_FLAG(bool, ShenandoahElasticTLAB, true, JVMFlag::DIAGNOSTIC, 200 "Use Elastic TLABs with Shenandoah"); 201 202 PRODUCT_FLAG(bool, ShenandoahAllowMixedAllocs, true, JVMFlag::DIAGNOSTIC, 203 "Allow mixing mutator and collector allocations into a single " 204 "region. Some heuristics enable/disable it for their needs"); 205 206 PRODUCT_FLAG(uintx, ShenandoahEvacReserve, 5, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 207 "How much of heap to reserve for evacuations. Larger values make " 208 "GC evacuate more live objects on every cycle, while leaving " 209 "less headroom for application to allocate in. In percents of " 210 "total heap size."); 211 FLAG_RANGE( ShenandoahEvacReserve, 1,100); 212 213 PRODUCT_FLAG(double, ShenandoahEvacWaste, 1.2, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 214 "How much waste evacuations produce within the reserved space. " 215 "Larger values make evacuations more resilient against " 216 "evacuation conflicts, at expense of evacuating less on each " 217 "GC cycle."); 218 FLAG_RANGE( ShenandoahEvacWaste, 1.0,100.0); 219 220 PRODUCT_FLAG(bool, ShenandoahEvacReserveOverflow, true, JVMFlag::EXPERIMENTAL, 221 "Allow evacuations to overflow the reserved space. Enabling it " 222 "will make evacuations more resilient when evacuation " 223 "reserve/waste is incorrect, at the risk that application " 224 "runs out of memory too early."); 225 226 PRODUCT_FLAG(bool, ShenandoahPacing, true, JVMFlag::EXPERIMENTAL, 227 "Pace application allocations to give GC chance to start " 228 "and complete before allocation failure is reached."); 229 230 PRODUCT_FLAG(uintx, ShenandoahPacingMaxDelay, 10, JVMFlag::EXPERIMENTAL, 231 "Max delay for pacing application allocations. Larger values " 232 "provide more resilience against out of memory, at expense at " 233 "hiding the GC latencies in the allocation path. Time is in " 234 "milliseconds. Setting it to arbitrarily large value makes " 235 "GC effectively stall the threads indefinitely instead of going " 236 "to degenerated or Full GC."); 237 238 PRODUCT_FLAG(uintx, ShenandoahPacingIdleSlack, 2, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 239 "How much of heap counted as non-taxable allocations during idle " 240 "phases. Larger value makes the pacing milder when collector is " 241 "idle, requiring less rendezvous with control thread. Lower " 242 "value makes the pacing control less responsive to out-of-cycle " 243 "allocs. In percent of total heap size."); 244 FLAG_RANGE( ShenandoahPacingIdleSlack, 0, 100); 245 246 PRODUCT_FLAG(uintx, ShenandoahPacingCycleSlack, 10, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 247 "How much of free space to take as non-taxable allocations " 248 "the GC cycle. Larger value makes the pacing milder at the " 249 "beginning of the GC cycle. Lower value makes the pacing less " 250 "uniform during the cycle. In percent of free space."); 251 FLAG_RANGE( ShenandoahPacingCycleSlack, 0, 100); 252 253 PRODUCT_FLAG(double, ShenandoahPacingSurcharge, 1.1, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 254 "Additional pacing tax surcharge to help unclutter the heap. " 255 "Larger values makes the pacing more aggressive. Lower values " 256 "risk GC cycles finish with less memory than were available at " 257 "the beginning of it."); 258 FLAG_RANGE( ShenandoahPacingSurcharge, 1.0, 100.0); 259 260 PRODUCT_FLAG(uintx, ShenandoahCriticalFreeThreshold, 1, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 261 "How much of the heap needs to be free after recovery cycles, " 262 "either Degenerated or Full GC to be claimed successful. If this " 263 "much space is not available, next recovery step would be " 264 "triggered."); 265 FLAG_RANGE( ShenandoahCriticalFreeThreshold, 0, 100); 266 267 PRODUCT_FLAG(bool, ShenandoahDegeneratedGC, true, JVMFlag::DIAGNOSTIC, 268 "Enable Degenerated GC as the graceful degradation step. " 269 "Disabling this option leads to degradation to Full GC instead. " 270 "When running in passive mode, this can be toggled to measure " 271 "either Degenerated GC or Full GC costs."); 272 273 PRODUCT_FLAG(uintx, ShenandoahFullGCThreshold, 3, JVMFlag::EXPERIMENTAL, 274 "How many back-to-back Degenerated GCs should happen before " 275 "going to a Full GC."); 276 277 PRODUCT_FLAG(bool, ShenandoahImplicitGCInvokesConcurrent, false, JVMFlag::EXPERIMENTAL, 278 "Should internally-caused GC requests invoke concurrent cycles, " 279 "should they do the stop-the-world (Degenerated / Full GC)? " 280 "Many heuristics automatically enable this. This option is " 281 "similar to global ExplicitGCInvokesConcurrent."); 282 283 PRODUCT_FLAG(bool, ShenandoahHumongousMoves, true, JVMFlag::DIAGNOSTIC, 284 "Allow moving humongous regions. This makes GC more resistant " 285 "to external fragmentation that may otherwise fail other " 286 "humongous allocations, at the expense of higher GC copying " 287 "costs. Currently affects stop-the-world (Full) cycle only."); 288 289 PRODUCT_FLAG(bool, ShenandoahOOMDuringEvacALot, false, JVMFlag::DIAGNOSTIC, 290 "Testing: simulate OOM during evacuation."); 291 292 PRODUCT_FLAG(bool, ShenandoahAllocFailureALot, false, JVMFlag::DIAGNOSTIC, 293 "Testing: make lots of artificial allocation failures."); 294 295 PRODUCT_FLAG(bool, ShenandoahAlwaysPreTouch, false, JVMFlag::DIAGNOSTIC, 296 "Pre-touch heap memory, overrides global AlwaysPreTouch."); 297 298 PRODUCT_FLAG(intx, ShenandoahMarkScanPrefetch, 32, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 299 "How many objects to prefetch ahead when traversing mark bitmaps." 300 "Set to 0 to disable prefetching."); 301 FLAG_RANGE( ShenandoahMarkScanPrefetch, 0, 256); 302 303 PRODUCT_FLAG(uintx, ShenandoahMarkLoopStride, 1000, JVMFlag::EXPERIMENTAL, 304 "How many items to process during one marking iteration before " 305 "checking for cancellation, yielding, etc. Larger values improve " 306 "marking performance at expense of responsiveness."); 307 308 PRODUCT_FLAG(uintx, ShenandoahParallelRegionStride, 1024, JVMFlag::EXPERIMENTAL, 309 "How many regions to process at once during parallel region " 310 "iteration. Affects heaps with lots of regions."); 311 312 PRODUCT_FLAG(size_t, ShenandoahSATBBufferSize, 1 * K, JVMFlag::EXPERIMENTAL | JVMFlag::RANGE, 313 "Number of entries in an SATB log buffer."); 314 FLAG_RANGE( ShenandoahSATBBufferSize, 1, max_uintx); 315 316 PRODUCT_FLAG(uintx, ShenandoahSATBBufferFlushInterval, 100, JVMFlag::EXPERIMENTAL, 317 "Forcefully flush non-empty SATB buffers at this interval. " 318 "Time is in milliseconds."); 319 320 PRODUCT_FLAG(bool, ShenandoahPreclean, true, JVMFlag::DIAGNOSTIC, 321 "Do concurrent preclean phase before final mark: process " 322 "definitely alive references to avoid dealing with them during " 323 "pause."); 324 325 PRODUCT_FLAG(bool, ShenandoahSuspendibleWorkers, false, JVMFlag::EXPERIMENTAL, 326 "Suspend concurrent GC worker threads at safepoints"); 327 328 PRODUCT_FLAG(bool, ShenandoahSATBBarrier, true, JVMFlag::DIAGNOSTIC, 329 "Turn on/off SATB barriers in Shenandoah"); 330 331 PRODUCT_FLAG(bool, ShenandoahStoreValEnqueueBarrier, false, JVMFlag::DIAGNOSTIC, 332 "Turn on/off enqueuing of oops for storeval barriers"); 333 334 PRODUCT_FLAG(bool, ShenandoahCASBarrier, true, JVMFlag::DIAGNOSTIC, 335 "Turn on/off CAS barriers in Shenandoah"); 336 337 PRODUCT_FLAG(bool, ShenandoahCloneBarrier, true, JVMFlag::DIAGNOSTIC, 338 "Turn on/off clone barriers in Shenandoah"); 339 340 PRODUCT_FLAG(bool, ShenandoahLoadRefBarrier, true, JVMFlag::DIAGNOSTIC, 341 "Turn on/off load-reference barriers in Shenandoah"); 342 343 PRODUCT_FLAG(bool, ShenandoahConcurrentScanCodeRoots, true, JVMFlag::DIAGNOSTIC, 344 "Scan code roots concurrently, instead of during a pause"); 345 346 PRODUCT_FLAG(uintx, ShenandoahCodeRootsStyle, 2, JVMFlag::DIAGNOSTIC, 347 "Use this style to scan the code cache roots:" 348 " 0 - sequential iterator;" 349 " 1 - parallel iterator;" 350 " 2 - parallel iterator with cset filters;"); 351 352 PRODUCT_FLAG(bool, ShenandoahOptimizeStaticFinals, true, JVMFlag::DIAGNOSTIC, 353 "Optimize barriers on static final fields. " 354 "Turn it off for maximum compatibility with reflection or JNI " 355 "code that manipulates final fields."); 356 357 DEVELOP_FLAG(bool, ShenandoahVerifyOptoBarriers, false, JVMFlag::DEFAULT, 358 "Verify no missing barriers in C2."); 359 360 PRODUCT_FLAG(bool, ShenandoahLoopOptsAfterExpansion, true, JVMFlag::DIAGNOSTIC, 361 "Attempt more loop opts after barrier expansion."); 362 363 PRODUCT_FLAG(bool, ShenandoahSelfFixing, true, JVMFlag::DIAGNOSTIC, 364 "Fix references with load reference barrier. Disabling this " 365 "might degrade performance."); 366 #endif // INCLUDE_SHENANDOAHGC 367 368 #endif // SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP