1 /* 2 * Copyright (c) 2016, 2020, Red Hat, Inc. All rights reserved. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. 7 * 8 * This code is distributed in the hope that it will be useful, but WITHOUT 9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 11 * version 2 for more details (a copy is included in the LICENSE file that 12 * accompanied this code). 13 * 14 * You should have received a copy of the GNU General Public License version 15 * 2 along with this work; if not, write to the Free Software Foundation, 16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 17 * 18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 19 * or visit www.oracle.com if you need additional information or have any 20 * questions. 21 * 22 */ 23 24 #ifndef SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP 25 #define SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP 26 27 #define GC_SHENANDOAH_FLAGS(develop, \ 28 develop_pd, \ 29 product, \ 30 product_pd, \ 31 diagnostic, \ 32 diagnostic_pd, \ 33 experimental, \ 34 notproduct, \ 35 manageable, \ 36 product_rw, \ 37 lp64_product, \ 38 range, \ 39 constraint, \ 40 writeable) \ 41 \ 42 experimental(size_t, ShenandoahRegionSize, 0, \ 43 "Static heap region size. Set zero to enable automatic sizing.") \ 44 \ 45 experimental(size_t, ShenandoahTargetNumRegions, 2048, \ 46 "With automatic region sizing, this is the approximate number " \ 47 "of regions that would be used, within min/max region size " \ 48 "limits.") \ 49 \ 50 experimental(size_t, ShenandoahMinRegionSize, 256 * K, \ 51 "With automatic region sizing, the regions would be at least " \ 52 "this large.") \ 53 \ 54 experimental(size_t, ShenandoahMaxRegionSize, 32 * M, \ 55 "With automatic region sizing, the regions would be at most " \ 56 "this large.") \ 57 \ 58 experimental(intx, ShenandoahHumongousThreshold, 100, \ 59 "Humongous objects are allocated in separate regions. " \ 60 "This setting defines how large the object should be to be " \ 61 "deemed humongous. Value is in percents of heap region size. " \ 62 "This also caps the maximum TLAB size.") \ 63 range(1, 100) \ 64 \ 65 product(ccstr, ShenandoahGCMode, "satb", \ 66 "GC mode to use. Among other things, this defines which " \ 67 "barriers are in in use. Possible values are:" \ 68 " satb - snapshot-at-the-beginning concurrent GC (three pass mark-evac-update);" \ 69 " iu - incremental-update concurrent GC (three pass mark-evac-update);" \ 70 " passive - stop the world GC only (either degenerated or full)") \ 71 \ 72 product(ccstr, ShenandoahGCHeuristics, "adaptive", \ 73 "GC heuristics to use. This fine-tunes the GC mode selected, " \ 74 "by choosing when to start the GC, how much to process on each " \ 75 "cycle, and what other features to automatically enable. " \ 76 "Possible values are:" \ 77 " adaptive - adapt to maintain the given amount of free heap " \ 78 "at all times, even during the GC cycle;" \ 79 " static - trigger GC when free heap falls below the threshold;" \ 80 " aggressive - run GC continuously, try to evacuate everything;" \ 81 " compact - run GC more frequently and with deeper targets to " \ 82 "free up more memory.") \ 83 \ 84 experimental(uintx, ShenandoahRefProcFrequency, 5, \ 85 "Process process weak (soft, phantom, finalizers) references " \ 86 "every Nth cycle. Normally affects concurrent GC cycles only, " \ 87 "as degenerated and full GCs would try to process references " \ 88 "regardless. Set to zero to disable reference processing " \ 89 "completely.") \ 90 \ 91 experimental(uintx, ShenandoahUnloadClassesFrequency, 5, \ 92 "Unload the classes every Nth cycle. Normally affects concurrent "\ 93 "GC cycles, as degenerated and full GCs would try to unload " \ 94 "classes regardless. Set to zero to disable class unloading.") \ 95 \ 96 experimental(uintx, ShenandoahGarbageThreshold, 25, \ 97 "How much garbage a region has to contain before it would be " \ 98 "taken for collection. This a guideline only, as GC heuristics " \ 99 "may select the region for collection even if it has little " \ 100 "garbage. This also affects how much internal fragmentation the " \ 101 "collector accepts. 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 experimental(uintx, ShenandoahEvacReserve, 5, \ 214 "How much of heap to reserve for evacuations. Larger values make "\ 215 "GC evacuate more live objects on every cycle, while leaving " \ 216 "less headroom for application to allocate in. In percents of " \ 217 "total heap size.") \ 218 range(1,100) \ 219 \ 220 experimental(double, ShenandoahEvacWaste, 1.2, \ 221 "How much waste evacuations produce within the reserved space. " \ 222 "Larger values make evacuations more resilient against " \ 223 "evacuation conflicts, at expense of evacuating less on each " \ 224 "GC cycle.") \ 225 range(1.0,100.0) \ 226 \ 227 experimental(bool, ShenandoahEvacReserveOverflow, true, \ 228 "Allow evacuations to overflow the reserved space. Enabling it " \ 229 "will make evacuations more resilient when evacuation " \ 230 "reserve/waste is incorrect, at the risk that application " \ 231 "runs out of memory too early.") \ 232 \ 233 experimental(bool, ShenandoahPacing, true, \ 234 "Pace application allocations to give GC chance to start " \ 235 "and complete before allocation failure is reached.") \ 236 \ 237 experimental(uintx, ShenandoahPacingMaxDelay, 10, \ 238 "Max delay for pacing application allocations. Larger values " \ 239 "provide more resilience against out of memory, at expense at " \ 240 "hiding the GC latencies in the allocation path. Time is in " \ 241 "milliseconds. Setting it to arbitrarily large value makes " \ 242 "GC effectively stall the threads indefinitely instead of going " \ 243 "to degenerated or Full GC.") \ 244 \ 245 experimental(uintx, ShenandoahPacingIdleSlack, 2, \ 246 "How much of heap counted as non-taxable allocations during idle "\ 247 "phases. Larger value makes the pacing milder when collector is " \ 248 "idle, requiring less rendezvous with control thread. Lower " \ 249 "value makes the pacing control less responsive to out-of-cycle " \ 250 "allocs. In percent of total heap size.") \ 251 range(0, 100) \ 252 \ 253 experimental(uintx, ShenandoahPacingCycleSlack, 10, \ 254 "How much of free space to take as non-taxable allocations " \ 255 "the GC cycle. Larger value makes the pacing milder at the " \ 256 "beginning of the GC cycle. Lower value makes the pacing less " \ 257 "uniform during the cycle. In percent of free space.") \ 258 range(0, 100) \ 259 \ 260 experimental(double, ShenandoahPacingSurcharge, 1.1, \ 261 "Additional pacing tax surcharge to help unclutter the heap. " \ 262 "Larger values makes the pacing more aggressive. Lower values " \ 263 "risk GC cycles finish with less memory than were available at " \ 264 "the beginning of it.") \ 265 range(1.0, 100.0) \ 266 \ 267 experimental(uintx, ShenandoahCriticalFreeThreshold, 1, \ 268 "How much of the heap needs to be free after recovery cycles, " \ 269 "either Degenerated or Full GC to be claimed successful. If this "\ 270 "much space is not available, next recovery step would be " \ 271 "triggered.") \ 272 range(0, 100) \ 273 \ 274 diagnostic(bool, ShenandoahDegeneratedGC, true, \ 275 "Enable Degenerated GC as the graceful degradation step. " \ 276 "Disabling this option leads to degradation to Full GC instead. " \ 277 "When running in passive mode, this can be toggled to measure " \ 278 "either Degenerated GC or Full GC costs.") \ 279 \ 280 experimental(uintx, ShenandoahFullGCThreshold, 3, \ 281 "How many back-to-back Degenerated GCs should happen before " \ 282 "going to a Full GC.") \ 283 \ 284 experimental(bool, ShenandoahImplicitGCInvokesConcurrent, false, \ 285 "Should internally-caused GC requests invoke concurrent cycles, " \ 286 "should they do the stop-the-world (Degenerated / Full GC)? " \ 287 "Many heuristics automatically enable this. This option is " \ 288 "similar to global ExplicitGCInvokesConcurrent.") \ 289 \ 290 diagnostic(bool, ShenandoahHumongousMoves, true, \ 291 "Allow moving humongous regions. This makes GC more resistant " \ 292 "to external fragmentation that may otherwise fail other " \ 293 "humongous allocations, at the expense of higher GC copying " \ 294 "costs. Currently affects stop-the-world (Full) cycle only.") \ 295 \ 296 diagnostic(bool, ShenandoahOOMDuringEvacALot, false, \ 297 "Testing: simulate OOM during evacuation.") \ 298 \ 299 diagnostic(bool, ShenandoahAllocFailureALot, false, \ 300 "Testing: make lots of artificial allocation failures.") \ 301 \ 302 experimental(intx, ShenandoahMarkScanPrefetch, 32, \ 303 "How many objects to prefetch ahead when traversing mark bitmaps."\ 304 "Set to 0 to disable prefetching.") \ 305 range(0, 256) \ 306 \ 307 experimental(uintx, ShenandoahMarkLoopStride, 1000, \ 308 "How many items to process during one marking iteration before " \ 309 "checking for cancellation, yielding, etc. Larger values improve "\ 310 "marking performance at expense of responsiveness.") \ 311 \ 312 experimental(uintx, ShenandoahParallelRegionStride, 1024, \ 313 "How many regions to process at once during parallel region " \ 314 "iteration. Affects heaps with lots of regions.") \ 315 \ 316 experimental(size_t, ShenandoahSATBBufferSize, 1 * K, \ 317 "Number of entries in an SATB log buffer.") \ 318 range(1, max_uintx) \ 319 \ 320 experimental(uintx, ShenandoahSATBBufferFlushInterval, 100, \ 321 "Forcefully flush non-empty SATB buffers at this interval. " \ 322 "Time is in milliseconds.") \ 323 \ 324 diagnostic(bool, ShenandoahPreclean, true, \ 325 "Do concurrent preclean phase before final mark: process " \ 326 "definitely alive references to avoid dealing with them during " \ 327 "pause.") \ 328 \ 329 experimental(bool, ShenandoahSuspendibleWorkers, false, \ 330 "Suspend concurrent GC worker threads at safepoints") \ 331 \ 332 diagnostic(bool, ShenandoahSATBBarrier, true, \ 333 "Turn on/off SATB barriers in Shenandoah") \ 334 \ 335 diagnostic(bool, ShenandoahStoreValEnqueueBarrier, false, \ 336 "Turn on/off enqueuing of oops for storeval barriers") \ 337 \ 338 diagnostic(bool, ShenandoahCASBarrier, true, \ 339 "Turn on/off CAS barriers in Shenandoah") \ 340 \ 341 diagnostic(bool, ShenandoahCloneBarrier, true, \ 342 "Turn on/off clone barriers in Shenandoah") \ 343 \ 344 diagnostic(bool, ShenandoahLoadRefBarrier, true, \ 345 "Turn on/off load-reference barriers in Shenandoah") \ 346 \ 347 diagnostic(uintx, ShenandoahCodeRootsStyle, 2, \ 348 "Use this style to scan the code cache roots:" \ 349 " 0 - sequential iterator;" \ 350 " 1 - parallel iterator;" \ 351 " 2 - parallel iterator with cset filters;") \ 352 \ 353 diagnostic(bool, ShenandoahOptimizeStaticFinals, true, \ 354 "Optimize barriers on static final fields. " \ 355 "Turn it off for maximum compatibility with reflection or JNI " \ 356 "code that manipulates final fields.") \ 357 \ 358 develop(bool, ShenandoahVerifyOptoBarriers, false, \ 359 "Verify no missing barriers in C2.") \ 360 \ 361 diagnostic(bool, ShenandoahLoopOptsAfterExpansion, true, \ 362 "Attempt more loop opts after barrier expansion.") \ 363 \ 364 diagnostic(bool, ShenandoahSelfFixing, true, \ 365 "Fix references with load reference barrier. Disabling this " \ 366 "might degrade performance.") \ 367 368 369 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP