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 #define GC_SHENANDOAH_FLAGS(develop, \ 30 develop_pd, \ 31 product, \ 32 product_pd, \ 33 diagnostic, \ 34 diagnostic_pd, \ 35 experimental, \ 36 notproduct, \ 37 manageable, \ 38 product_rw, \ 39 lp64_product, \ 40 range, \ 41 constraint) \ 42 \ 43 experimental(size_t, ShenandoahRegionSize, 0, \ 44 "Static heap region size. Set zero to enable automatic sizing.") \ 45 \ 46 experimental(size_t, ShenandoahTargetNumRegions, 2048, \ 47 "With automatic region sizing, this is the approximate number " \ 48 "of regions that would be used, within min/max region size " \ 49 "limits.") \ 50 \ 51 experimental(size_t, ShenandoahMinRegionSize, 256 * K, \ 52 "With automatic region sizing, the regions would be at least " \ 53 "this large.") \ 54 \ 55 experimental(size_t, ShenandoahMaxRegionSize, 32 * M, \ 56 "With automatic region sizing, the regions would be at most " \ 57 "this large.") \ 58 \ 59 experimental(intx, ShenandoahHumongousThreshold, 100, \ 60 "Humongous objects are allocated in separate regions. " \ 61 "This setting defines how large the object should be to be " \ 62 "deemed humongous. Value is in percents of heap region size. " \ 63 "This also caps the maximum TLAB size.") \ 64 range(1, 100) \ 65 \ 66 product(ccstr, ShenandoahGCMode, "satb", \ 67 "GC mode to use. Among other things, this defines which " \ 68 "barriers are in in use. Possible values are:" \ 69 " satb - snapshot-at-the-beginning concurrent GC (three pass mark-evac-update);" \ 70 " iu - incremental-update concurrent GC (three pass mark-evac-update);" \ 71 " passive - stop the world GC only (either degenerated or full)") \ 72 \ 73 product(ccstr, ShenandoahGCHeuristics, "adaptive", \ 74 "GC heuristics to use. This fine-tunes the GC mode selected, " \ 75 "by choosing when to start the GC, how much to process on each " \ 76 "cycle, and what other features to automatically enable. " \ 77 "Possible values are:" \ 78 " adaptive - adapt to maintain the given amount of free heap " \ 79 "at all times, even during the GC cycle;" \ 80 " static - trigger GC when free heap falls below the threshold;" \ 81 " aggressive - run GC continuously, try to evacuate everything;" \ 82 " compact - run GC more frequently and with deeper targets to " \ 83 "free up more memory.") \ 84 \ 85 experimental(uintx, ShenandoahRefProcFrequency, 5, \ 86 "Process process weak (soft, phantom, finalizers) references " \ 87 "every Nth cycle. Normally affects concurrent GC cycles only, " \ 88 "as degenerated and full GCs would try to process references " \ 89 "regardless. Set to zero to disable reference processing " \ 90 "completely.") \ 91 \ 92 experimental(uintx, ShenandoahUnloadClassesFrequency, 1, \ 93 "Unload the classes every Nth cycle. Normally affects concurrent "\ 94 "GC cycles, as degenerated and full GCs would try to unload " \ 95 "classes regardless. Set to zero to disable class unloading.") \ 96 \ 97 experimental(uintx, ShenandoahGarbageThreshold, 25, \ 98 "How much garbage a region has to contain before it would be " \ 99 "taken for collection. This a guideline only, as GC heuristics " \ 100 "may select the region for collection even if it has little " \ 101 "garbage. This also affects how much internal fragmentation the " \ 102 "collector accepts. In percents of heap region size.") \ 103 range(0,100) \ 104 \ 105 experimental(uintx, ShenandoahInitFreeThreshold, 70, \ 106 "How much heap should be free before some heuristics trigger the "\ 107 "initial (learning) cycles. Affects cycle frequency on startup " \ 108 "and after drastic state changes, e.g. after degenerated/full " \ 109 "GC cycles. In percents of total heap size.") \ 110 range(0,100) \ 111 \ 112 experimental(uintx, ShenandoahMinFreeThreshold, 10, \ 113 "How much heap should be free before most heuristics trigger the "\ 114 "collection, even without other triggers. Provides the safety " \ 115 "margin for many heuristics. In percents of total heap size.") \ 116 range(0,100) \ 117 \ 118 experimental(uintx, ShenandoahAllocationThreshold, 0, \ 119 "How many new allocations should happen since the last GC cycle " \ 120 "before some heuristics trigger the collection. In percents of " \ 121 "total heap size. Set to zero to effectively disable.") \ 122 range(0,100) \ 123 \ 124 experimental(uintx, ShenandoahAllocSpikeFactor, 5, \ 125 "How much of heap should some heuristics reserve for absorbing " \ 126 "the allocation spikes. Larger value wastes more memory in " \ 127 "non-emergency cases, but provides more safety in emergency " \ 128 "cases. In percents of total heap size.") \ 129 range(0,100) \ 130 \ 131 experimental(uintx, ShenandoahLearningSteps, 5, \ 132 "The number of cycles some heuristics take to collect in order " \ 133 "to learn application and GC performance.") \ 134 range(0,100) \ 135 \ 136 experimental(uintx, ShenandoahImmediateThreshold, 90, \ 137 "The cycle may shortcut when enough garbage can be reclaimed " \ 138 "from the immediate garbage (completely garbage regions). " \ 139 "In percents of total garbage found. Setting this threshold " \ 140 "to 100 effectively disables the shortcut.") \ 141 range(0,100) \ 142 \ 143 experimental(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, \ 144 "Many heuristics would guarantee a concurrent GC cycle at " \ 145 "least with this interval. This is useful when large idle " \ 146 "intervals are present, where GC can run without stealing " \ 147 "time from active application. Time is in milliseconds. " \ 148 "Setting this to 0 disables the feature.") \ 149 \ 150 experimental(bool, ShenandoahAlwaysClearSoftRefs, false, \ 151 "Unconditionally clear soft references, instead of using any " \ 152 "other cleanup policy. This minimizes footprint at expense of" \ 153 "more soft reference churn in applications.") \ 154 \ 155 experimental(bool, ShenandoahUncommit, true, \ 156 "Allow to uncommit memory under unused regions and metadata. " \ 157 "This optimizes footprint at expense of allocation latency in " \ 158 "regions that require committing back. Uncommits would be " \ 159 "disabled by some heuristics, or with static heap size.") \ 160 \ 161 experimental(uintx, ShenandoahUncommitDelay, 5*60*1000, \ 162 "Uncommit memory for regions that were not used for more than " \ 163 "this time. First use after that would incur allocation stalls. " \ 164 "Actively used regions would never be uncommitted, because they " \ 165 "do not become unused longer than this delay. Time is in " \ 166 "milliseconds. Setting this delay to 0 effectively uncommits " \ 167 "regions almost immediately after they become unused.") \ 168 \ 169 experimental(bool, ShenandoahRegionSampling, false, \ 170 "Provide heap region sampling data via jvmstat.") \ 171 \ 172 experimental(int, ShenandoahRegionSamplingRate, 40, \ 173 "Sampling rate for heap region sampling. In milliseconds between "\ 174 "the samples. Higher values provide more fidelity, at expense " \ 175 "of more sampling overhead.") \ 176 \ 177 experimental(uintx, ShenandoahControlIntervalMin, 1, \ 178 "The minimum sleep interval for the control loop that drives " \ 179 "the cycles. Lower values would increase GC responsiveness " \ 180 "to changing heap conditions, at the expense of higher perf " \ 181 "overhead. Time is in milliseconds.") \ 182 \ 183 experimental(uintx, ShenandoahControlIntervalMax, 10, \ 184 "The maximum sleep interval for control loop that drives " \ 185 "the cycles. Lower values would increase GC responsiveness " \ 186 "to changing heap conditions, at the expense of higher perf " \ 187 "overhead. Time is in milliseconds.") \ 188 \ 189 experimental(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, \ 190 "The time period for one step in control loop interval " \ 191 "adjustment. Lower values make adjustments faster, at the " \ 192 "expense of higher perf overhead. Time is in milliseconds.") \ 193 \ 194 experimental(bool, ShenandoahCriticalControlThreadPriority, false, \ 195 "Run control thread runs at critical scheduling priority.") \ 196 \ 197 diagnostic(bool, ShenandoahVerify, false, \ 198 "Enable internal verification. This would catch many GC bugs, " \ 199 "but it would also stall the collector during the verification, " \ 200 "which prolongs the pauses and might hide other bugs.") \ 201 \ 202 diagnostic(intx, ShenandoahVerifyLevel, 4, \ 203 "Verification level, higher levels check more, taking more time. "\ 204 "Accepted values are:" \ 205 " 0 = basic heap checks; " \ 206 " 1 = previous level, plus basic region checks; " \ 207 " 2 = previous level, plus all roots; " \ 208 " 3 = previous level, plus all reachable objects; " \ 209 " 4 = previous level, plus all marked objects") \ 210 \ 211 diagnostic(bool, ShenandoahElasticTLAB, true, \ 212 "Use Elastic TLABs with Shenandoah") \ 213 \ 214 experimental(uintx, ShenandoahEvacReserve, 5, \ 215 "How much of heap to reserve for evacuations. Larger values make "\ 216 "GC evacuate more live objects on every cycle, while leaving " \ 217 "less headroom for application to allocate in. In percents of " \ 218 "total heap size.") \ 219 range(1,100) \ 220 \ 221 experimental(double, ShenandoahEvacWaste, 1.2, \ 222 "How much waste evacuations produce within the reserved space. " \ 223 "Larger values make evacuations more resilient against " \ 224 "evacuation conflicts, at expense of evacuating less on each " \ 225 "GC cycle.") \ 226 range(1.0,100.0) \ 227 \ 228 experimental(bool, ShenandoahEvacReserveOverflow, true, \ 229 "Allow evacuations to overflow the reserved space. Enabling it " \ 230 "will make evacuations more resilient when evacuation " \ 231 "reserve/waste is incorrect, at the risk that application " \ 232 "runs out of memory too early.") \ 233 \ 234 experimental(bool, ShenandoahPacing, true, \ 235 "Pace application allocations to give GC chance to start " \ 236 "and complete before allocation failure is reached.") \ 237 \ 238 experimental(uintx, ShenandoahPacingMaxDelay, 10, \ 239 "Max delay for pacing application allocations. Larger values " \ 240 "provide more resilience against out of memory, at expense at " \ 241 "hiding the GC latencies in the allocation path. Time is in " \ 242 "milliseconds. Setting it to arbitrarily large value makes " \ 243 "GC effectively stall the threads indefinitely instead of going " \ 244 "to degenerated or Full GC.") \ 245 \ 246 experimental(uintx, ShenandoahPacingIdleSlack, 2, \ 247 "How much of heap counted as non-taxable allocations during idle "\ 248 "phases. Larger value makes the pacing milder when collector is " \ 249 "idle, requiring less rendezvous with control thread. Lower " \ 250 "value makes the pacing control less responsive to out-of-cycle " \ 251 "allocs. In percent of total heap size.") \ 252 range(0, 100) \ 253 \ 254 experimental(uintx, ShenandoahPacingCycleSlack, 10, \ 255 "How much of free space to take as non-taxable allocations " \ 256 "the GC cycle. Larger value makes the pacing milder at the " \ 257 "beginning of the GC cycle. Lower value makes the pacing less " \ 258 "uniform during the cycle. In percent of free space.") \ 259 range(0, 100) \ 260 \ 261 experimental(double, ShenandoahPacingSurcharge, 1.1, \ 262 "Additional pacing tax surcharge to help unclutter the heap. " \ 263 "Larger values makes the pacing more aggressive. Lower values " \ 264 "risk GC cycles finish with less memory than were available at " \ 265 "the beginning of it.") \ 266 range(1.0, 100.0) \ 267 \ 268 experimental(uintx, ShenandoahCriticalFreeThreshold, 1, \ 269 "How much of the heap needs to be free after recovery cycles, " \ 270 "either Degenerated or Full GC to be claimed successful. If this "\ 271 "much space is not available, next recovery step would be " \ 272 "triggered.") \ 273 range(0, 100) \ 274 \ 275 diagnostic(bool, ShenandoahDegeneratedGC, true, \ 276 "Enable Degenerated GC as the graceful degradation step. " \ 277 "Disabling this option leads to degradation to Full GC instead. " \ 278 "When running in passive mode, this can be toggled to measure " \ 279 "either Degenerated GC or Full GC costs.") \ 280 \ 281 experimental(uintx, ShenandoahFullGCThreshold, 3, \ 282 "How many back-to-back Degenerated GCs should happen before " \ 283 "going to a Full GC.") \ 284 \ 285 experimental(bool, ShenandoahImplicitGCInvokesConcurrent, false, \ 286 "Should internally-caused GC requests invoke concurrent cycles, " \ 287 "should they do the stop-the-world (Degenerated / Full GC)? " \ 288 "Many heuristics automatically enable this. This option is " \ 289 "similar to global ExplicitGCInvokesConcurrent.") \ 290 \ 291 diagnostic(bool, ShenandoahHumongousMoves, true, \ 292 "Allow moving humongous regions. This makes GC more resistant " \ 293 "to external fragmentation that may otherwise fail other " \ 294 "humongous allocations, at the expense of higher GC copying " \ 295 "costs. Currently affects stop-the-world (Full) cycle only.") \ 296 \ 297 diagnostic(bool, ShenandoahOOMDuringEvacALot, false, \ 298 "Testing: simulate OOM during evacuation.") \ 299 \ 300 diagnostic(bool, ShenandoahAllocFailureALot, false, \ 301 "Testing: make lots of artificial allocation failures.") \ 302 \ 303 experimental(intx, ShenandoahMarkScanPrefetch, 32, \ 304 "How many objects to prefetch ahead when traversing mark bitmaps."\ 305 "Set to 0 to disable prefetching.") \ 306 range(0, 256) \ 307 \ 308 experimental(uintx, ShenandoahMarkLoopStride, 1000, \ 309 "How many items to process during one marking iteration before " \ 310 "checking for cancellation, yielding, etc. Larger values improve "\ 311 "marking performance at expense of responsiveness.") \ 312 \ 313 experimental(uintx, ShenandoahParallelRegionStride, 1024, \ 314 "How many regions to process at once during parallel region " \ 315 "iteration. Affects heaps with lots of regions.") \ 316 \ 317 experimental(size_t, ShenandoahSATBBufferSize, 1 * K, \ 318 "Number of entries in an SATB log buffer.") \ 319 range(1, max_uintx) \ 320 \ 321 experimental(uintx, ShenandoahSATBBufferFlushInterval, 100, \ 322 "Forcefully flush non-empty SATB buffers at this interval. " \ 323 "Time is in milliseconds.") \ 324 \ 325 diagnostic(bool, ShenandoahPreclean, true, \ 326 "Do concurrent preclean phase before final mark: process " \ 327 "definitely alive references to avoid dealing with them during " \ 328 "pause.") \ 329 \ 330 experimental(bool, ShenandoahSuspendibleWorkers, false, \ 331 "Suspend concurrent GC worker threads at safepoints") \ 332 \ 333 diagnostic(bool, ShenandoahSATBBarrier, true, \ 334 "Turn on/off SATB barriers in Shenandoah") \ 335 \ 336 diagnostic(bool, ShenandoahStoreValEnqueueBarrier, false, \ 337 "Turn on/off enqueuing of oops for storeval barriers") \ 338 \ 339 diagnostic(bool, ShenandoahCASBarrier, true, \ 340 "Turn on/off CAS barriers in Shenandoah") \ 341 \ 342 diagnostic(bool, ShenandoahCloneBarrier, true, \ 343 "Turn on/off clone barriers in Shenandoah") \ 344 \ 345 diagnostic(bool, ShenandoahLoadRefBarrier, true, \ 346 "Turn on/off load-reference barriers in Shenandoah") \ 347 \ 348 diagnostic(bool, ShenandoahConcurrentScanCodeRoots, true, \ 349 "Scan code roots concurrently, instead of during a pause") \ 350 \ 351 diagnostic(uintx, ShenandoahCodeRootsStyle, 2, \ 352 "Use this style to scan the code cache roots:" \ 353 " 0 - sequential iterator;" \ 354 " 1 - parallel iterator;" \ 355 " 2 - parallel iterator with cset filters;") \ 356 \ 357 diagnostic(bool, ShenandoahOptimizeStaticFinals, true, \ 358 "Optimize barriers on static final fields. " \ 359 "Turn it off for maximum compatibility with reflection or JNI " \ 360 "code that manipulates final fields.") \ 361 \ 362 develop(bool, ShenandoahVerifyOptoBarriers, false, \ 363 "Verify no missing barriers in C2.") \ 364 \ 365 diagnostic(bool, ShenandoahLoopOptsAfterExpansion, true, \ 366 "Attempt more loop opts after barrier expansion.") \ 367 \ 368 diagnostic(bool, ShenandoahSelfFixing, true, \ 369 "Fix references with load reference barrier. Disabling this " \ 370 "might degrade performance.") \ 371 372 373 #endif // SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP