1 /* 2 * Copyright (c) 2016, 2018, 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 #include "runtime/globals.hpp" 28 29 #define SHENANDOAH_FLAGS(develop, \ 30 develop_pd, \ 31 product, \ 32 product_pd, \ 33 diagnostic, \ 34 experimental, \ 35 notproduct, \ 36 manageable, \ 37 product_rw) \ 38 \ 39 experimental(uintx, ShenandoahRegionSize, 0, \ 40 "Static heap region size. Set zero to enable automatic sizing.") \ 41 \ 42 experimental(uintx, ShenandoahTargetNumRegions, 2048, \ 43 "With automatic region sizing, this is the approximate number " \ 44 "of regions that would be used, within min/max region size " \ 45 "limits.") \ 46 \ 47 experimental(uintx, ShenandoahMinRegionSize, 256 * K, \ 48 "With automatic region sizing, the regions would be at least " \ 49 "this large.") \ 50 \ 51 experimental(uintx, ShenandoahMaxRegionSize, 32 * M, \ 52 "With automatic region sizing, the regions would be at most " \ 53 "this large.") \ 54 \ 55 experimental(intx, ShenandoahHumongousThreshold, 100, \ 56 "Humongous objects are allocated in separate regions. " \ 57 "This setting defines how large the object should be to be " \ 58 "deemed humongous. Value is in percents of heap region size. " \ 59 "This also caps the maximum TLAB size.") \ 60 \ 61 product(ccstr, ShenandoahGCMode, "satb", \ 62 "GC mode to use. Among other things, this defines which " \ 63 "barriers are in in use. Possible values are:" \ 64 " satb - snapshot-at-the-beginning concurrent GC (three pass mark-evac-update);" \ 65 " iu - incremental-update concurrent GC (three pass mark-evac-update);" \ 66 " passive - stop the world GC only (either degenerated or full)") \ 67 \ 68 product(ccstr, ShenandoahGCHeuristics, "adaptive", \ 69 "GC heuristics to use. This fine-tunes the GC mode selected, " \ 70 "by choosing when to start the GC, how much to process on each " \ 71 "cycle, and what other features to automatically enable. " \ 72 "Possible values are:" \ 73 " adaptive - adapt to maintain the given amount of free heap " \ 74 "at all times, even during the GC cycle;" \ 75 " static - trigger GC when free heap falls below the threshold;" \ 76 " aggressive - run GC continuously, try to evacuate everything;" \ 77 " compact - run GC more frequently and with deeper targets to " \ 78 "free up more memory.") \ 79 \ 80 experimental(uintx, ShenandoahRefProcFrequency, 5, \ 81 "Process process weak (soft, phantom, finalizers) references " \ 82 "every Nth cycle. Normally affects concurrent GC cycles only, " \ 83 "as degenerated and full GCs would try to process references " \ 84 "regardless. Set to zero to disable reference processing " \ 85 "completely.") \ 86 \ 87 experimental(uintx, ShenandoahUnloadClassesFrequency, 100, \ 88 "Unload the classes every Nth cycle. Normally affects concurrent "\ 89 "GC cycles, as degenerated and full GCs would try to unload " \ 90 "classes regardless. Set to zero to disable class unloading.") \ 91 \ 92 experimental(uintx, ShenandoahGarbageThreshold, 25, \ 93 "How much garbage a region has to contain before it would be " \ 94 "taken for collection. This a guideline only, as GC heuristics " \ 95 "may select the region for collection even if it has little " \ 96 "garbage. This also affects how much internal fragmentation the " \ 97 "collector accepts. In percents of heap region size.") \ 98 \ 99 experimental(uintx, ShenandoahInitFreeThreshold, 70, \ 100 "How much heap should be free before some heuristics trigger the "\ 101 "initial (learning) cycles. Affects cycle frequency on startup " \ 102 "and after drastic state changes, e.g. after degenerated/full " \ 103 "GC cycles. In percents of total heap size.") \ 104 \ 105 experimental(uintx, ShenandoahMinFreeThreshold, 10, \ 106 "How much heap should be free before most heuristics trigger the "\ 107 "collection, even without other triggers. Provides the safety " \ 108 "margin for many heuristics. In percents of total heap size.") \ 109 \ 110 experimental(uintx, ShenandoahAllocationThreshold, 0, \ 111 "How many new allocations should happen since the last GC cycle " \ 112 "before some heuristics trigger the collection. In percents of " \ 113 "total heap size. Set to zero to effectively disable.") \ 114 \ 115 experimental(uintx, ShenandoahAllocSpikeFactor, 5, \ 116 "How much of heap should some heuristics reserve for absorbing " \ 117 "the allocation spikes. Larger value wastes more memory in " \ 118 "non-emergency cases, but provides more safety in emergency " \ 119 "cases. In percents of total heap size.") \ 120 \ 121 experimental(uintx, ShenandoahLearningSteps, 5, \ 122 "The number of cycles some heuristics take to collect in order " \ 123 "to learn application and GC performance.") \ 124 \ 125 experimental(uintx, ShenandoahImmediateThreshold, 90, \ 126 "The cycle may shortcut when enough garbage can be reclaimed " \ 127 "from the immediate garbage (completely garbage regions). " \ 128 "In percents of total garbage found. Setting this threshold " \ 129 "to 100 effectively disables the shortcut.") \ 130 \ 131 experimental(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, \ 132 "Many heuristics would guarantee a concurrent GC cycle at " \ 133 "at 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 experimental(bool, ShenandoahAlwaysClearSoftRefs, false, \ 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 experimental(bool, ShenandoahUncommit, true, \ 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 experimental(uintx, ShenandoahUncommitDelay, 5*60*1000, \ 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 experimental(bool, ShenandoahRegionSampling, false, \ 158 "Provide heap region sampling data via jvmstat.") \ 159 \ 160 experimental(int, ShenandoahRegionSamplingRate, 40, \ 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 experimental(uintx, ShenandoahControlIntervalMin, 1, \ 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 experimental(uintx, ShenandoahControlIntervalMax, 10, \ 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 experimental(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, \ 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 diagnostic(bool, ShenandoahVerify, false, \ 183 "Enable internal verification. This would catch many GC bugs, " \ 184 "but it would also stall the collector during the verification, " \ 185 "which prolongs the pauses and might hide other bugs.") \ 186 \ 187 diagnostic(intx, ShenandoahVerifyLevel, 4, \ 188 "Verification level, higher levels check more, taking more time. "\ 189 "Accepted values are:" \ 190 " 0 = basic heap checks; " \ 191 " 1 = previous level, plus basic region checks; " \ 192 " 2 = previous level, plus all roots; " \ 193 " 3 = previous level, plus all reachable objects; " \ 194 " 4 = previous level, plus all marked objects") \ 195 \ 196 diagnostic(bool, ShenandoahElasticTLAB, true, \ 197 "Use Elastic TLABs with Shenandoah") \ 198 \ 199 experimental(uintx, ShenandoahEvacReserve, 5, \ 200 "How much of heap to reserve for evacuations. Larger values make "\ 201 "GC evacuate more live objects on every cycle, while leaving " \ 202 "less headroom for application to allocate in. In percents of " \ 203 "total heap size.") \ 204 \ 205 experimental(double, ShenandoahEvacWaste, 1.2, \ 206 "How much waste evacuations produce within the reserved space. " \ 207 "Larger values make evacuations more resilient against " \ 208 "evacuation conflicts, at expense of evacuating less on each " \ 209 "GC cycle.") \ 210 \ 211 experimental(bool, ShenandoahEvacReserveOverflow, true, \ 212 "Allow evacuations to overflow the reserved space. Enabling it " \ 213 "will make evacuations more resilient when evacuation " \ 214 "reserve/waste is incorrect, at the risk that application " \ 215 "runs out of memory too early.") \ 216 \ 217 experimental(bool, ShenandoahPacing, true, \ 218 "Pace application allocations to give GC chance to start " \ 219 "and complete before allocation failure is reached.") \ 220 \ 221 experimental(uintx, ShenandoahPacingMaxDelay, 10, \ 222 "Max delay for pacing application allocations. Larger values " \ 223 "provide more resilience against out of memory, at expense at " \ 224 "hiding the GC latencies in the allocation path. Time is in " \ 225 "milliseconds. Setting it to arbitrarily large value makes " \ 226 "GC effectively stall the threads indefinitely instead of going " \ 227 "to degenerated or Full GC.") \ 228 \ 229 experimental(uintx, ShenandoahPacingIdleSlack, 2, \ 230 "How much of heap counted as non-taxable allocations during idle "\ 231 "phases. Larger value makes the pacing milder when collector is " \ 232 "idle, requiring less rendezvous with control thread. Lower " \ 233 "value makes the pacing control less responsive to out-of-cycle " \ 234 "allocs. In percent of total heap size.") \ 235 \ 236 experimental(uintx, ShenandoahPacingCycleSlack, 10, \ 237 "How much of free space to take as non-taxable allocations " \ 238 "the GC cycle. Larger value makes the pacing milder at the " \ 239 "beginning of the GC cycle. Lower value makes the pacing less " \ 240 "uniform during the cycle. In percent of free space.") \ 241 \ 242 experimental(double, ShenandoahPacingSurcharge, 1.1, \ 243 "Additional pacing tax surcharge to help unclutter the heap. " \ 244 "Larger values makes the pacing more aggressive. Lower values " \ 245 "risk GC cycles finish with less memory than were available at " \ 246 "the beginning of it.") \ 247 \ 248 experimental(uintx, ShenandoahCriticalFreeThreshold, 1, \ 249 "How much of the heap needs to be free after recovery cycles, " \ 250 "either Degenerated or Full GC to be claimed successful. If this "\ 251 "much space is not available, next recovery step would be " \ 252 "triggered.") \ 253 \ 254 diagnostic(bool, ShenandoahDegeneratedGC, true, \ 255 "Enable Degenerated GC as the graceful degradation step. " \ 256 "Disabling this option leads to degradation to Full GC instead. " \ 257 "When running in passive mode, this can be toggled to measure " \ 258 "either Degenerated GC or Full GC costs.") \ 259 \ 260 experimental(uintx, ShenandoahFullGCThreshold, 3, \ 261 "How many back-to-back Degenerated GCs should happen before " \ 262 "going to a Full GC.") \ 263 \ 264 experimental(bool, ShenandoahImplicitGCInvokesConcurrent, false, \ 265 "Should internally-caused GC requests invoke concurrent cycles, " \ 266 "should they do the stop-the-world (Degenerated / Full GC)? " \ 267 "Many heuristics automatically enable this. This option is " \ 268 "similar to global ExplicitGCInvokesConcurrent.") \ 269 \ 270 diagnostic(bool, ShenandoahHumongousMoves, true, \ 271 "Allow moving humongous regions. This makes GC more resistant " \ 272 "to external fragmentation that may otherwise fail other " \ 273 "humongous allocations, at the expense of higher GC copying " \ 274 "costs. Currently affects stop-the-world (Full) cycle only.") \ 275 \ 276 diagnostic(bool, ShenandoahOOMDuringEvacALot, false, \ 277 "Testing: simulate OOM during evacuation.") \ 278 \ 279 diagnostic(bool, ShenandoahAllocFailureALot, false, \ 280 "Testing: make lots of artificial allocation failures.") \ 281 \ 282 experimental(intx, ShenandoahMarkScanPrefetch, 32, \ 283 "How many objects to prefetch ahead when traversing mark bitmaps."\ 284 "Set to 0 to disable prefetching.") \ 285 \ 286 experimental(uintx, ShenandoahMarkLoopStride, 1000, \ 287 "How many items to process during one marking iteration before " \ 288 "checking for cancellation, yielding, etc. Larger values improve "\ 289 "marking performance at expense of responsiveness.") \ 290 \ 291 experimental(uintx, ShenandoahParallelRegionStride, 1024, \ 292 "How many regions to process at once during parallel region " \ 293 "iteration. Affects heaps with lots of regions.") \ 294 \ 295 experimental(intx, ShenandoahSATBBufferSize, 1 * K, \ 296 "Number of entries in an SATB log buffer.") \ 297 \ 298 experimental(uintx, ShenandoahSATBBufferFlushInterval, 100, \ 299 "Forcefully flush non-empty SATB buffers at this interval. " \ 300 "Time is in milliseconds.") \ 301 \ 302 diagnostic(bool, ShenandoahPreclean, true, \ 303 "Do concurrent preclean phase before final mark: process " \ 304 "definitely alive references to avoid dealing with them during " \ 305 "pause.") \ 306 \ 307 diagnostic(bool, ShenandoahSATBBarrier, true, \ 308 "Turn on/off SATB barriers in Shenandoah") \ 309 \ 310 diagnostic(bool, ShenandoahStoreValEnqueueBarrier, false, \ 311 "Turn on/off enqueuing of oops for storeval barriers") \ 312 \ 313 diagnostic(bool, ShenandoahCASBarrier, true, \ 314 "Turn on/off CAS barriers in Shenandoah") \ 315 \ 316 diagnostic(bool, ShenandoahCloneBarrier, true, \ 317 "Turn on/off clone barriers in Shenandoah") \ 318 \ 319 diagnostic(bool, ShenandoahLoadRefBarrier, true, \ 320 "Turn on/off load-reference barriers in Shenandoah") \ 321 \ 322 diagnostic(uintx, ShenandoahCodeRootsStyle, 2, \ 323 "Use this style to scan the code cache roots:" \ 324 " 0 - sequential iterator;" \ 325 " 1 - parallel iterator;" \ 326 " 2 - parallel iterator with cset filters;") \ 327 \ 328 diagnostic(bool, ShenandoahOptimizeStaticFinals, true, \ 329 "Optimize barriers on static final fields. " \ 330 "Turn it off for maximum compatibility with reflection or JNI " \ 331 "code that manipulates final fields.") \ 332 \ 333 develop(bool, ShenandoahVerifyOptoBarriers, false, \ 334 "Verify no missing barriers in C2.") \ 335 \ 336 product(bool, ShenandoahLogTrace, false, \ 337 "Turns on logging in Shenandoah at trace level. ") \ 338 \ 339 product(bool, ShenandoahLogDebug, false, \ 340 "Turns on logging in Shenandoah at debug level. ") \ 341 \ 342 product(bool, ShenandoahLogInfo, false, \ 343 "Turns on logging in Shenandoah at info level. ") \ 344 \ 345 product(bool, ShenandoahLogWarning, false, \ 346 "Turns on logging in Shenandoah at warning level. ") \ 347 \ 348 349 SHENANDOAH_FLAGS(DECLARE_DEVELOPER_FLAG, \ 350 DECLARE_PD_DEVELOPER_FLAG, \ 351 DECLARE_PRODUCT_FLAG, \ 352 DECLARE_PD_PRODUCT_FLAG, \ 353 DECLARE_DIAGNOSTIC_FLAG, \ 354 DECLARE_EXPERIMENTAL_FLAG, \ 355 DECLARE_NOTPRODUCT_FLAG, \ 356 DECLARE_MANAGEABLE_FLAG, \ 357 DECLARE_PRODUCT_RW_FLAG) 358 359 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP