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, ShenandoahHeapRegionSize, 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 experimental(ccstr, ShenandoahGCMode, "normal", \ 67 "GC mode to use. Among other things, this defines which " \ 68 "barriers are in in use. Possible values are:" \ 69 " normal - default concurrent GC (three pass mark-evac-update);" \ 70 " traversal - traversal concurrent GC (single-pass); " \ 71 " passive - stop the world GC only (either degenerated or full)") \ 72 \ 73 experimental(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, 60, \ 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. In percents of heap region size.") \ 102 range(0,100) \ 103 \ 104 experimental(uintx, ShenandoahInitFreeThreshold, 70, \ 105 "How much heap should be free before some heuristics trigger the "\ 106 "initial (learning) cycles. Affects cycle frequency on startup " \ 107 "and after drastic state changes, e.g. after degenerated/full " \ 108 "GC cycles. In percents of total heap size.") \ 109 range(0,100) \ 110 \ 111 experimental(uintx, ShenandoahMinFreeThreshold, 10, \ 112 "How much heap should be free before most heuristics trigger the "\ 113 "collection, even without other triggers. Provides the safety " \ 114 "margin for many heuristics. In percents of total heap size.") \ 115 range(0,100) \ 116 \ 117 experimental(uintx, ShenandoahAllocationThreshold, 0, \ 118 "How many new allocations should happen since the last GC cycle " \ 119 "before some heuristics trigger the collection. In percents of " \ 120 "total heap size. Set to zero to effectively disable.") \ 121 range(0,100) \ 122 \ 123 experimental(uintx, ShenandoahAllocSpikeFactor, 5, \ 124 "How much of heap should some heuristics reserve for absorbing " \ 125 "the allocation spikes. Larger value wastes more memory in " \ 126 "non-emergency cases, but provides more safety in emergency " \ 127 "cases. In percents of total heap size.") \ 128 range(0,100) \ 129 \ 130 experimental(uintx, ShenandoahLearningSteps, 5, \ 131 "The number of cycles some heuristics take to collect in order " \ 132 "to learn application and GC performance.") \ 133 range(0,100) \ 134 \ 135 experimental(uintx, ShenandoahImmediateThreshold, 90, \ 136 "The cycle may shortcut when enough garbage can be reclaimed " \ 137 "from the immediate garbage (completely garbage regions). " \ 138 "In percents of total garbage found. Setting this threshold " \ 139 "to 100 effectively disables the shortcut.") \ 140 range(0,100) \ 141 \ 142 experimental(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, \ 143 "Many heuristics would guarantee a concurrent GC cycle at " \ 144 "least with this interval. This is useful when large idle " \ 145 "intervals are present, where GC can run without stealing " \ 146 "time from active application. Time is in milliseconds. " \ 147 "Setting this to 0 disables the feature.") \ 148 \ 149 experimental(bool, ShenandoahAlwaysClearSoftRefs, false, \ 150 "Unconditionally clear soft references, instead of using any " \ 151 "other cleanup policy. This minimizes footprint at expense of" \ 152 "more soft reference churn in applications.") \ 153 \ 154 experimental(bool, ShenandoahUncommit, true, \ 155 "Allow to uncommit memory under unused regions and metadata. " \ 156 "This optimizes footprint at expense of allocation latency in " \ 157 "regions that require committing back. Uncommits would be " \ 158 "disabled by some heuristics, or with static heap size.") \ 159 \ 160 experimental(uintx, ShenandoahUncommitDelay, 5*60*1000, \ 161 "Uncommit memory for regions that were not used for more than " \ 162 "this time. First use after that would incur allocation stalls. " \ 163 "Actively used regions would never be uncommitted, because they " \ 164 "do not become unused longer than this delay. Time is in " \ 165 "milliseconds. Setting this delay to 0 effectively uncommits " \ 166 "regions almost immediately after they become unused.") \ 167 \ 168 experimental(bool, ShenandoahRegionSampling, false, \ 169 "Provide heap region sampling data via jvmstat.") \ 170 \ 171 experimental(int, ShenandoahRegionSamplingRate, 40, \ 172 "Sampling rate for heap region sampling. In milliseconds between "\ 173 "the samples. Higher values provide more fidelity, at expense " \ 174 "of more sampling overhead.") \ 175 \ 176 experimental(uintx, ShenandoahControlIntervalMin, 1, \ 177 "The minimum sleep interval for the control loop that drives " \ 178 "the cycles. Lower values would increase GC responsiveness " \ 179 "to changing heap conditions, at the expense of higher perf " \ 180 "overhead. Time is in milliseconds.") \ 181 \ 182 experimental(uintx, ShenandoahControlIntervalMax, 10, \ 183 "The maximum sleep interval for control loop that drives " \ 184 "the cycles. Lower values would increase GC responsiveness " \ 185 "to changing heap conditions, at the expense of higher perf " \ 186 "overhead. Time is in milliseconds.") \ 187 \ 188 experimental(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, \ 189 "The time period for one step in control loop interval " \ 190 "adjustment. Lower values make adjustments faster, at the " \ 191 "expense of higher perf overhead. Time is in milliseconds.") \ 192 \ 193 experimental(bool, ShenandoahCriticalControlThreadPriority, false, \ 194 "Run control thread runs at critical scheduling priority.") \ 195 \ 196 diagnostic(bool, ShenandoahVerify, false, \ 197 "Enable internal verification. This would catch many GC bugs, " \ 198 "but it would also stall the collector during the verification, " \ 199 "which prolongs the pauses and might hide other bugs.") \ 200 \ 201 diagnostic(intx, ShenandoahVerifyLevel, 4, \ 202 "Verification level, higher levels check more, taking more time. "\ 203 "Accepted values are:" \ 204 " 0 = basic heap checks; " \ 205 " 1 = previous level, plus basic region checks; " \ 206 " 2 = previous level, plus all roots; " \ 207 " 3 = previous level, plus all reachable objects; " \ 208 " 4 = previous level, plus all marked objects") \ 209 \ 210 diagnostic(bool, ShenandoahElasticTLAB, true, \ 211 "Use Elastic TLABs with Shenandoah") \ 212 \ 213 diagnostic(bool, ShenandoahAllowMixedAllocs, true, \ 214 "Allow mixing mutator and collector allocations into a single " \ 215 "region. Some heuristics enable/disable it for their needs") \ 216 \ 217 experimental(uintx, ShenandoahEvacReserve, 5, \ 218 "How much of heap to reserve for evacuations. Larger values make "\ 219 "GC evacuate more live objects on every cycle, while leaving " \ 220 "less headroom for application to allocate in. In percents of " \ 221 "total heap size.") \ 222 range(1,100) \ 223 \ 224 experimental(double, ShenandoahEvacWaste, 1.2, \ 225 "How much waste evacuations produce within the reserved space. " \ 226 "Larger values make evacuations more resilient against " \ 227 "evacuation conflicts, at expense of evacuating less on each " \ 228 "GC cycle.") \ 229 range(1.0,100.0) \ 230 \ 231 experimental(bool, ShenandoahEvacReserveOverflow, true, \ 232 "Allow evacuations to overflow the reserved space. Enabling it " \ 233 "will make evacuations more resilient when evacuation " \ 234 "reserve/waste is incorrect, at the risk that application " \ 235 "runs out of memory too early.") \ 236 \ 237 experimental(bool, ShenandoahPacing, true, \ 238 "Pace application allocations to give GC chance to start " \ 239 "and complete before allocation failure is reached.") \ 240 \ 241 experimental(uintx, ShenandoahPacingMaxDelay, 10, \ 242 "Max delay for pacing application allocations. Larger values " \ 243 "provide more resilience against out of memory, at expense at " \ 244 "hiding the GC latencies in the allocation path. Time is in " \ 245 "milliseconds. Setting it to arbitrarily large value makes " \ 246 "GC effectively stall the threads indefinitely instead of going " \ 247 "to degenerated or Full GC.") \ 248 \ 249 experimental(uintx, ShenandoahPacingIdleSlack, 2, \ 250 "How much of heap counted as non-taxable allocations during idle "\ 251 "phases. Larger value makes the pacing milder when collector is " \ 252 "idle, requiring less rendezvous with control thread. Lower " \ 253 "value makes the pacing control less responsive to out-of-cycle " \ 254 "allocs. In percent of total heap size.") \ 255 range(0, 100) \ 256 \ 257 experimental(uintx, ShenandoahPacingCycleSlack, 10, \ 258 "How much of free space to take as non-taxable allocations " \ 259 "the GC cycle. Larger value makes the pacing milder at the " \ 260 "beginning of the GC cycle. Lower value makes the pacing less " \ 261 "uniform during the cycle. In percent of free space.") \ 262 range(0, 100) \ 263 \ 264 experimental(double, ShenandoahPacingSurcharge, 1.1, \ 265 "Additional pacing tax surcharge to help unclutter the heap. " \ 266 "Larger values makes the pacing more aggressive. Lower values " \ 267 "risk GC cycles finish with less memory than were available at " \ 268 "the beginning of it.") \ 269 range(1.0, 100.0) \ 270 \ 271 experimental(uintx, ShenandoahCriticalFreeThreshold, 1, \ 272 "How much of the heap needs to be free after recovery cycles, " \ 273 "either Degenerated or Full GC to be claimed successful. If this "\ 274 "much space is not available, next recovery step would be " \ 275 "triggered.") \ 276 range(0, 100) \ 277 \ 278 diagnostic(bool, ShenandoahDegeneratedGC, true, \ 279 "Enable Degenerated GC as the graceful degradation step. " \ 280 "Disabling this option leads to degradation to Full GC instead. " \ 281 "When running in passive mode, this can be toggled to measure " \ 282 "either Degenerated GC or Full GC costs.") \ 283 \ 284 experimental(uintx, ShenandoahFullGCThreshold, 3, \ 285 "How many back-to-back Degenerated GCs should happen before " \ 286 "going to a Full GC.") \ 287 \ 288 experimental(bool, ShenandoahImplicitGCInvokesConcurrent, false, \ 289 "Should internally-caused GC requests invoke concurrent cycles, " \ 290 "should they do the stop-the-world (Degenerated / Full GC)? " \ 291 "Many heuristics automatically enable this. This option is " \ 292 "similar to global ExplicitGCInvokesConcurrent.") \ 293 \ 294 diagnostic(bool, ShenandoahHumongousMoves, true, \ 295 "Allow moving humongous regions. This makes GC more resistant " \ 296 "to external fragmentation that may otherwise fail other " \ 297 "humongous allocations, at the expense of higher GC copying " \ 298 "costs. Currently affects stop-the-world (Full) cycle only.") \ 299 \ 300 diagnostic(bool, ShenandoahOOMDuringEvacALot, false, \ 301 "Testing: simulate OOM during evacuation.") \ 302 \ 303 diagnostic(bool, ShenandoahAllocFailureALot, false, \ 304 "Testing: make lots of artificial allocation failures.") \ 305 \ 306 diagnostic(bool, ShenandoahAlwaysPreTouch, false, \ 307 "Pre-touch heap memory, overrides global AlwaysPreTouch.") \ 308 \ 309 experimental(intx, ShenandoahMarkScanPrefetch, 32, \ 310 "How many objects to prefetch ahead when traversing mark bitmaps."\ 311 "Set to 0 to disable prefetching.") \ 312 range(0, 256) \ 313 \ 314 experimental(uintx, ShenandoahMarkLoopStride, 1000, \ 315 "How many items to process during one marking iteration before " \ 316 "checking for cancellation, yielding, etc. Larger values improve "\ 317 "marking performance at expense of responsiveness.") \ 318 \ 319 experimental(uintx, ShenandoahParallelRegionStride, 1024, \ 320 "How many regions to process at once during parallel region " \ 321 "iteration. Affects heaps with lots of regions.") \ 322 \ 323 experimental(size_t, ShenandoahSATBBufferSize, 1 * K, \ 324 "Number of entries in an SATB log buffer.") \ 325 range(1, max_uintx) \ 326 \ 327 experimental(uintx, ShenandoahSATBBufferFlushInterval, 100, \ 328 "Forcefully flush non-empty SATB buffers at this interval. " \ 329 "Time is in milliseconds.") \ 330 \ 331 diagnostic(bool, ShenandoahPreclean, true, \ 332 "Do concurrent preclean phase before final mark: process " \ 333 "definitely alive references to avoid dealing with them during " \ 334 "pause.") \ 335 \ 336 experimental(bool, ShenandoahSuspendibleWorkers, false, \ 337 "Suspend concurrent GC worker threads at safepoints") \ 338 \ 339 diagnostic(bool, ShenandoahSATBBarrier, true, \ 340 "Turn on/off SATB barriers in Shenandoah") \ 341 \ 342 diagnostic(bool, ShenandoahStoreValEnqueueBarrier, false, \ 343 "Turn on/off enqueuing of oops for storeval barriers") \ 344 \ 345 diagnostic(bool, ShenandoahCASBarrier, true, \ 346 "Turn on/off CAS barriers in Shenandoah") \ 347 \ 348 diagnostic(bool, ShenandoahCloneBarrier, true, \ 349 "Turn on/off clone barriers in Shenandoah") \ 350 \ 351 diagnostic(bool, ShenandoahLoadRefBarrier, true, \ 352 "Turn on/off load-reference barriers in Shenandoah") \ 353 \ 354 diagnostic(bool, ShenandoahConcurrentScanCodeRoots, true, \ 355 "Scan code roots concurrently, instead of during a pause") \ 356 \ 357 diagnostic(uintx, ShenandoahCodeRootsStyle, 2, \ 358 "Use this style to scan the code cache roots:" \ 359 " 0 - sequential iterator;" \ 360 " 1 - parallel iterator;" \ 361 " 2 - parallel iterator with cset filters;") \ 362 \ 363 diagnostic(bool, ShenandoahOptimizeStaticFinals, true, \ 364 "Optimize barriers on static final fields. " \ 365 "Turn it off for maximum compatibility with reflection or JNI " \ 366 "code that manipulates final fields.") \ 367 \ 368 develop(bool, ShenandoahVerifyOptoBarriers, false, \ 369 "Verify no missing barriers in C2.") \ 370 \ 371 diagnostic(bool, ShenandoahLoopOptsAfterExpansion, true, \ 372 "Attempt more loop opts after barrier expansion.") \ 373 \ 374 diagnostic(bool, ShenandoahSelfFixing, true, \ 375 "Fix references with load reference barrier. Disabling this " \ 376 "might degrade performance.") \ 377 378 379 #endif // SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP