| /* |
| * Copyright (c) 2016, 2020, Red Hat, Inc. All rights reserved. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #ifndef SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP |
| #define SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP |
| |
| #define GC_SHENANDOAH_FLAGS(develop, \ |
| develop_pd, \ |
| product, \ |
| product_pd, \ |
| diagnostic, \ |
| diagnostic_pd, \ |
| experimental, \ |
| notproduct, \ |
| manageable, \ |
| product_rw, \ |
| lp64_product, \ |
| range, \ |
| constraint, \ |
| writeable) \ |
| \ |
| experimental(size_t, ShenandoahRegionSize, 0, \ |
| "Static heap region size. Set zero to enable automatic sizing.") \ |
| \ |
| experimental(size_t, ShenandoahTargetNumRegions, 2048, \ |
| "With automatic region sizing, this is the approximate number " \ |
| "of regions that would be used, within min/max region size " \ |
| "limits.") \ |
| \ |
| experimental(size_t, ShenandoahMinRegionSize, 256 * K, \ |
| "With automatic region sizing, the regions would be at least " \ |
| "this large.") \ |
| \ |
| experimental(size_t, ShenandoahMaxRegionSize, 32 * M, \ |
| "With automatic region sizing, the regions would be at most " \ |
| "this large.") \ |
| \ |
| experimental(intx, ShenandoahHumongousThreshold, 100, \ |
| "Humongous objects are allocated in separate regions. " \ |
| "This setting defines how large the object should be to be " \ |
| "deemed humongous. Value is in percents of heap region size. " \ |
| "This also caps the maximum TLAB size.") \ |
| range(1, 100) \ |
| \ |
| product(ccstr, ShenandoahGCMode, "satb", \ |
| "GC mode to use. Among other things, this defines which " \ |
| "barriers are in in use. Possible values are:" \ |
| " satb - snapshot-at-the-beginning concurrent GC (three pass mark-evac-update);" \ |
| " iu - incremental-update concurrent GC (three pass mark-evac-update);" \ |
| " passive - stop the world GC only (either degenerated or full)") \ |
| \ |
| product(ccstr, ShenandoahGCHeuristics, "adaptive", \ |
| "GC heuristics to use. This fine-tunes the GC mode selected, " \ |
| "by choosing when to start the GC, how much to process on each " \ |
| "cycle, and what other features to automatically enable. " \ |
| "Possible values are:" \ |
| " adaptive - adapt to maintain the given amount of free heap " \ |
| "at all times, even during the GC cycle;" \ |
| " static - trigger GC when free heap falls below the threshold;" \ |
| " aggressive - run GC continuously, try to evacuate everything;" \ |
| " compact - run GC more frequently and with deeper targets to " \ |
| "free up more memory.") \ |
| \ |
| experimental(uintx, ShenandoahRefProcFrequency, 5, \ |
| "Process process weak (soft, phantom, finalizers) references " \ |
| "every Nth cycle. Normally affects concurrent GC cycles only, " \ |
| "as degenerated and full GCs would try to process references " \ |
| "regardless. Set to zero to disable reference processing " \ |
| "completely.") \ |
| \ |
| experimental(uintx, ShenandoahUnloadClassesFrequency, 100, \ |
| "Unload the classes every Nth cycle. Normally affects concurrent "\ |
| "GC cycles, as degenerated and full GCs would try to unload " \ |
| "classes regardless. Set to zero to disable class unloading.") \ |
| \ |
| experimental(uintx, ShenandoahGarbageThreshold, 25, \ |
| "How much garbage a region has to contain before it would be " \ |
| "taken for collection. This a guideline only, as GC heuristics " \ |
| "may select the region for collection even if it has little " \ |
| "garbage. This also affects how much internal fragmentation the " \ |
| "collector accepts. In percents of heap region size.") \ |
| range(0,100) \ |
| \ |
| experimental(uintx, ShenandoahInitFreeThreshold, 70, \ |
| "How much heap should be free before some heuristics trigger the "\ |
| "initial (learning) cycles. Affects cycle frequency on startup " \ |
| "and after drastic state changes, e.g. after degenerated/full " \ |
| "GC cycles. In percents of (soft) max heap size.") \ |
| range(0,100) \ |
| \ |
| experimental(uintx, ShenandoahMinFreeThreshold, 10, \ |
| "How much heap should be free before most heuristics trigger the "\ |
| "collection, even without other triggers. Provides the safety " \ |
| "margin for many heuristics. In percents of (soft) max heap size.")\ |
| range(0,100) \ |
| \ |
| experimental(uintx, ShenandoahAllocationThreshold, 0, \ |
| "How many new allocations should happen since the last GC cycle " \ |
| "before some heuristics trigger the collection. In percents of " \ |
| "(soft) max heap size. Set to zero to effectively disable.") \ |
| range(0,100) \ |
| \ |
| experimental(uintx, ShenandoahAllocSpikeFactor, 5, \ |
| "How much of heap should some heuristics reserve for absorbing " \ |
| "the allocation spikes. Larger value wastes more memory in " \ |
| "non-emergency cases, but provides more safety in emergency " \ |
| "cases. In percents of (soft) max heap size.") \ |
| range(0,100) \ |
| \ |
| experimental(uintx, ShenandoahLearningSteps, 5, \ |
| "The number of cycles some heuristics take to collect in order " \ |
| "to learn application and GC performance.") \ |
| range(0,100) \ |
| \ |
| experimental(uintx, ShenandoahImmediateThreshold, 90, \ |
| "The cycle may shortcut when enough garbage can be reclaimed " \ |
| "from the immediate garbage (completely garbage regions). " \ |
| "In percents of total garbage found. Setting this threshold " \ |
| "to 100 effectively disables the shortcut.") \ |
| range(0,100) \ |
| \ |
| experimental(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, \ |
| "Many heuristics would guarantee a concurrent GC cycle at " \ |
| "least with this interval. This is useful when large idle " \ |
| "intervals are present, where GC can run without stealing " \ |
| "time from active application. Time is in milliseconds. " \ |
| "Setting this to 0 disables the feature.") \ |
| \ |
| experimental(bool, ShenandoahAlwaysClearSoftRefs, false, \ |
| "Unconditionally clear soft references, instead of using any " \ |
| "other cleanup policy. This minimizes footprint at expense of" \ |
| "more soft reference churn in applications.") \ |
| \ |
| experimental(bool, ShenandoahUncommit, true, \ |
| "Allow to uncommit memory under unused regions and metadata. " \ |
| "This optimizes footprint at expense of allocation latency in " \ |
| "regions that require committing back. Uncommits would be " \ |
| "disabled by some heuristics, or with static heap size.") \ |
| \ |
| experimental(uintx, ShenandoahUncommitDelay, 5*60*1000, \ |
| "Uncommit memory for regions that were not used for more than " \ |
| "this time. First use after that would incur allocation stalls. " \ |
| "Actively used regions would never be uncommitted, because they " \ |
| "do not become unused longer than this delay. Time is in " \ |
| "milliseconds. Setting this delay to 0 effectively uncommits " \ |
| "regions almost immediately after they become unused.") \ |
| \ |
| experimental(bool, ShenandoahRegionSampling, false, \ |
| "Provide heap region sampling data via jvmstat.") \ |
| \ |
| experimental(int, ShenandoahRegionSamplingRate, 40, \ |
| "Sampling rate for heap region sampling. In milliseconds between "\ |
| "the samples. Higher values provide more fidelity, at expense " \ |
| "of more sampling overhead.") \ |
| \ |
| experimental(uintx, ShenandoahControlIntervalMin, 1, \ |
| "The minimum sleep interval for the control loop that drives " \ |
| "the cycles. Lower values would increase GC responsiveness " \ |
| "to changing heap conditions, at the expense of higher perf " \ |
| "overhead. Time is in milliseconds.") \ |
| \ |
| experimental(uintx, ShenandoahControlIntervalMax, 10, \ |
| "The maximum sleep interval for control loop that drives " \ |
| "the cycles. Lower values would increase GC responsiveness " \ |
| "to changing heap conditions, at the expense of higher perf " \ |
| "overhead. Time is in milliseconds.") \ |
| \ |
| experimental(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, \ |
| "The time period for one step in control loop interval " \ |
| "adjustment. Lower values make adjustments faster, at the " \ |
| "expense of higher perf overhead. Time is in milliseconds.") \ |
| \ |
| diagnostic(bool, ShenandoahVerify, false, \ |
| "Enable internal verification. This would catch many GC bugs, " \ |
| "but it would also stall the collector during the verification, " \ |
| "which prolongs the pauses and might hide other bugs.") \ |
| \ |
| diagnostic(intx, ShenandoahVerifyLevel, 4, \ |
| "Verification level, higher levels check more, taking more time. "\ |
| "Accepted values are:" \ |
| " 0 = basic heap checks; " \ |
| " 1 = previous level, plus basic region checks; " \ |
| " 2 = previous level, plus all roots; " \ |
| " 3 = previous level, plus all reachable objects; " \ |
| " 4 = previous level, plus all marked objects") \ |
| \ |
| diagnostic(bool, ShenandoahElasticTLAB, true, \ |
| "Use Elastic TLABs with Shenandoah") \ |
| \ |
| experimental(uintx, ShenandoahEvacReserve, 5, \ |
| "How much of heap to reserve for evacuations. Larger values make "\ |
| "GC evacuate more live objects on every cycle, while leaving " \ |
| "less headroom for application to allocate in. In percents of " \ |
| "total heap size.") \ |
| range(1,100) \ |
| \ |
| experimental(double, ShenandoahEvacWaste, 1.2, \ |
| "How much waste evacuations produce within the reserved space. " \ |
| "Larger values make evacuations more resilient against " \ |
| "evacuation conflicts, at expense of evacuating less on each " \ |
| "GC cycle.") \ |
| range(1.0,100.0) \ |
| \ |
| experimental(bool, ShenandoahEvacReserveOverflow, true, \ |
| "Allow evacuations to overflow the reserved space. Enabling it " \ |
| "will make evacuations more resilient when evacuation " \ |
| "reserve/waste is incorrect, at the risk that application " \ |
| "runs out of memory too early.") \ |
| \ |
| experimental(bool, ShenandoahPacing, true, \ |
| "Pace application allocations to give GC chance to start " \ |
| "and complete before allocation failure is reached.") \ |
| \ |
| experimental(uintx, ShenandoahPacingMaxDelay, 10, \ |
| "Max delay for pacing application allocations. Larger values " \ |
| "provide more resilience against out of memory, at expense at " \ |
| "hiding the GC latencies in the allocation path. Time is in " \ |
| "milliseconds. Setting it to arbitrarily large value makes " \ |
| "GC effectively stall the threads indefinitely instead of going " \ |
| "to degenerated or Full GC.") \ |
| \ |
| experimental(uintx, ShenandoahPacingIdleSlack, 2, \ |
| "How much of heap counted as non-taxable allocations during idle "\ |
| "phases. Larger value makes the pacing milder when collector is " \ |
| "idle, requiring less rendezvous with control thread. Lower " \ |
| "value makes the pacing control less responsive to out-of-cycle " \ |
| "allocs. In percent of total heap size.") \ |
| range(0, 100) \ |
| \ |
| experimental(uintx, ShenandoahPacingCycleSlack, 10, \ |
| "How much of free space to take as non-taxable allocations " \ |
| "the GC cycle. Larger value makes the pacing milder at the " \ |
| "beginning of the GC cycle. Lower value makes the pacing less " \ |
| "uniform during the cycle. In percent of free space.") \ |
| range(0, 100) \ |
| \ |
| experimental(double, ShenandoahPacingSurcharge, 1.1, \ |
| "Additional pacing tax surcharge to help unclutter the heap. " \ |
| "Larger values makes the pacing more aggressive. Lower values " \ |
| "risk GC cycles finish with less memory than were available at " \ |
| "the beginning of it.") \ |
| range(1.0, 100.0) \ |
| \ |
| experimental(uintx, ShenandoahCriticalFreeThreshold, 1, \ |
| "How much of the heap needs to be free after recovery cycles, " \ |
| "either Degenerated or Full GC to be claimed successful. If this "\ |
| "much space is not available, next recovery step would be " \ |
| "triggered.") \ |
| range(0, 100) \ |
| \ |
| diagnostic(bool, ShenandoahDegeneratedGC, true, \ |
| "Enable Degenerated GC as the graceful degradation step. " \ |
| "Disabling this option leads to degradation to Full GC instead. " \ |
| "When running in passive mode, this can be toggled to measure " \ |
| "either Degenerated GC or Full GC costs.") \ |
| \ |
| experimental(uintx, ShenandoahFullGCThreshold, 3, \ |
| "How many back-to-back Degenerated GCs should happen before " \ |
| "going to a Full GC.") \ |
| \ |
| experimental(bool, ShenandoahImplicitGCInvokesConcurrent, false, \ |
| "Should internally-caused GC requests invoke concurrent cycles, " \ |
| "should they do the stop-the-world (Degenerated / Full GC)? " \ |
| "Many heuristics automatically enable this. This option is " \ |
| "similar to global ExplicitGCInvokesConcurrent.") \ |
| \ |
| diagnostic(bool, ShenandoahHumongousMoves, true, \ |
| "Allow moving humongous regions. This makes GC more resistant " \ |
| "to external fragmentation that may otherwise fail other " \ |
| "humongous allocations, at the expense of higher GC copying " \ |
| "costs. Currently affects stop-the-world (Full) cycle only.") \ |
| \ |
| diagnostic(bool, ShenandoahOOMDuringEvacALot, false, \ |
| "Testing: simulate OOM during evacuation.") \ |
| \ |
| diagnostic(bool, ShenandoahAllocFailureALot, false, \ |
| "Testing: make lots of artificial allocation failures.") \ |
| \ |
| experimental(intx, ShenandoahMarkScanPrefetch, 32, \ |
| "How many objects to prefetch ahead when traversing mark bitmaps."\ |
| "Set to 0 to disable prefetching.") \ |
| range(0, 256) \ |
| \ |
| experimental(uintx, ShenandoahMarkLoopStride, 1000, \ |
| "How many items to process during one marking iteration before " \ |
| "checking for cancellation, yielding, etc. Larger values improve "\ |
| "marking performance at expense of responsiveness.") \ |
| \ |
| experimental(uintx, ShenandoahParallelRegionStride, 1024, \ |
| "How many regions to process at once during parallel region " \ |
| "iteration. Affects heaps with lots of regions.") \ |
| \ |
| experimental(size_t, ShenandoahSATBBufferSize, 1 * K, \ |
| "Number of entries in an SATB log buffer.") \ |
| range(1, max_uintx) \ |
| \ |
| experimental(uintx, ShenandoahMaxSATBBufferFlushes, 5, \ |
| "How many times to maximum attempt to flush SATB buffers at the " \ |
| "end of concurrent marking.") \ |
| \ |
| diagnostic(bool, ShenandoahPreclean, true, \ |
| "Do concurrent preclean phase before final mark: process " \ |
| "definitely alive references to avoid dealing with them during " \ |
| "pause.") \ |
| \ |
| experimental(bool, ShenandoahSuspendibleWorkers, false, \ |
| "Suspend concurrent GC worker threads at safepoints") \ |
| \ |
| diagnostic(bool, ShenandoahSATBBarrier, true, \ |
| "Turn on/off SATB barriers in Shenandoah") \ |
| \ |
| diagnostic(bool, ShenandoahIUBarrier, false, \ |
| "Turn on/off I-U barriers barriers in Shenandoah") \ |
| \ |
| diagnostic(bool, ShenandoahCASBarrier, true, \ |
| "Turn on/off CAS barriers in Shenandoah") \ |
| \ |
| diagnostic(bool, ShenandoahCloneBarrier, true, \ |
| "Turn on/off clone barriers in Shenandoah") \ |
| \ |
| diagnostic(bool, ShenandoahLoadRefBarrier, true, \ |
| "Turn on/off load-reference barriers in Shenandoah") \ |
| \ |
| diagnostic(uintx, ShenandoahCodeRootsStyle, 2, \ |
| "Use this style to scan the code cache roots:" \ |
| " 0 - sequential iterator;" \ |
| " 1 - parallel iterator;" \ |
| " 2 - parallel iterator with cset filters;") \ |
| \ |
| diagnostic(bool, ShenandoahOptimizeStaticFinals, true, \ |
| "Optimize barriers on static final fields. " \ |
| "Turn it off for maximum compatibility with reflection or JNI " \ |
| "code that manipulates final fields.") \ |
| \ |
| develop(bool, ShenandoahVerifyOptoBarriers, false, \ |
| "Verify no missing barriers in C2.") \ |
| \ |
| diagnostic(bool, ShenandoahLoopOptsAfterExpansion, true, \ |
| "Attempt more loop opts after barrier expansion.") \ |
| \ |
| diagnostic(bool, ShenandoahSelfFixing, true, \ |
| "Fix references with load reference barrier. Disabling this " \ |
| "might degrade performance.") \ |
| \ |
| manageable(size_t, ShenandoahSoftMaxHeapSize, 0, \ |
| "Soft limit for maximum heap size (in bytes)") \ |
| |
| #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP |
