/* * Copyright (c) 2016, 2018, 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, ShenandoahHeapRegionSize, 0, \ "Size of the Shenandoah regions. Set to zero to detect " \ "automatically.") \ \ experimental(size_t, ShenandoahTargetNumRegions, 2048, \ "Target number of regions. We try to get around that many " \ "regions, based on Shenandoah{Min,Max}RegionSize.") \ \ experimental(size_t, ShenandoahMinRegionSize, 256 * K, \ "Minimum Shenandoah heap region size.") \ \ experimental(size_t, ShenandoahMaxRegionSize, 32 * M, \ "Maximum Shenandoah heap region size.") \ \ experimental(intx, ShenandoahHumongousThreshold, 100, \ "How large should the object be to get allocated in humongous " \ "region, in percents of heap region size. This also caps the " \ "maximum TLAB size.") \ range(1, 100) \ \ experimental(ccstr, ShenandoahGCHeuristics, "adaptive", \ "The heuristics to use in Shenandoah GC. Possible values:" \ " *) adaptive - adapt to maintain the given amount of free heap;" \ " *) static - start concurrent GC when static free heap " \ " threshold and static allocation threshold are " \ " tripped;" \ " *) passive - do not start concurrent GC, wait for Full GC; " \ " *) aggressive - run concurrent GC continuously, evacuate " \ " everything;" \ " *) compact - run GC with lower footprint target, may end up " \ " doing continuous GC, evacuate lots of live " \ " objects, uncommit heap aggressively;") \ \ experimental(ccstr, ShenandoahUpdateRefsEarly, "adaptive", \ "Run a separate concurrent reference updating phase after" \ "concurrent evacuation. Possible values: 'on', 'off', 'adaptive'")\ \ experimental(uintx, ShenandoahRefProcFrequency, 5, \ "How often should (weak, soft, etc) references be processed. " \ "References get processed at every Nth GC cycle. Set to zero " \ "to disable reference processing.") \ \ experimental(uintx, ShenandoahUnloadClassesFrequency, 5, \ "How often should classes get unloaded. " \ "Class unloading is performed at every Nth GC cycle. " \ "Set to zero to disable class unloading during concurrent GC.") \ \ experimental(uintx, ShenandoahGarbageThreshold, 60, \ "Sets the percentage of garbage a region need to contain before " \ "it can be marked for collection. Does not apply to all " \ "heuristics.") \ range(0,100) \ \ experimental(uintx, ShenandoahFreeThreshold, 10, \ "Set the percentage of free heap at which a GC cycle is started. "\ "Does not apply to all heuristics.") \ range(0,100) \ \ experimental(uintx, ShenandoahInitFreeThreshold, 70, \ "Initial remaining free heap threshold for learning steps in " \ "heuristics. In percents of total heap size. Does not apply to " \ "all heuristics.") \ range(0,100) \ \ experimental(uintx, ShenandoahMinFreeThreshold, 10, \ "Minimum remaining free space threshold, after which collection " \ "definitely triggers. Does not apply to all heuristics.") \ range(0,100) \ \ experimental(uintx, ShenandoahAllocationThreshold, 0, \ "Set percentage of memory allocated since last GC cycle before " \ "a new GC cycle can be started. Set to zero to effectively " \ "disable.") \ range(0,100) \ \ experimental(uintx, ShenandoahLearningSteps, 5, \ "Number of GC cycles to run in order to learn application " \ "and GC performance for adaptive heuristics.") \ range(0,100) \ \ experimental(uintx, ShenandoahImmediateThreshold, 90, \ "If mark identifies more than this much immediate garbage " \ "regions, it shall recycle them, and shall not continue the " \ "rest of the GC cycle. The value is in percents of total " \ "number of candidate regions for collection set. Setting this " \ "threshold to 100% effectively disables this shortcut.") \ range(0,100) \ \ experimental(uintx, ShenandoahMergeUpdateRefsMinGap, 100, \ "If GC is currently running in separate update-refs mode " \ "this numbers gives the threshold when to switch to " \ "merged update-refs mode. Number is percentage relative to" \ "duration(marking)+duration(update-refs).") \ \ experimental(uintx, ShenandoahMergeUpdateRefsMaxGap, 200, \ "If GC is currently running in merged update-refs mode " \ "this numbers gives the threshold when to switch to " \ "separate update-refs mode. Number is percentage relative " \ "to duration(marking)+duration(update-refs).") \ \ experimental(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, \ "Adaptive and dynamic heuristics would guarantee a 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.") \ \ experimental(bool, ShenandoahAlwaysClearSoftRefs, false, \ "Clear soft references always, instead of using any smart " \ "cleanup policy. This minimizes footprint at expense of more " \ "softref churn in applications.") \ \ experimental(bool, ShenandoahUncommit, true, \ "Allow Shenandoah to uncommit unused memory.") \ \ experimental(uintx, ShenandoahUncommitDelay, 5*60*1000, \ "Shenandoah would start to 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 never decay. Time is in milliseconds." \ "Setting this delay to 0 effectively makes Shenandoah to " \ "uncommit the regions almost immediately.") \ \ experimental(bool, ShenandoahRegionSampling, false, \ "Turns on heap region sampling via JVMStat") \ \ experimental(int, ShenandoahRegionSamplingRate, 40, \ "Sampling rate for heap region sampling. " \ "Number of milliseconds between samples") \ \ experimental(uintx, ShenandoahControlIntervalMin, 1, \ "The minumum 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, 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, \ "Verify the Shenandoah garbage collector") \ \ diagnostic(intx, ShenandoahVerifyLevel, 4, \ "Shenandoah verification level: " \ "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") \ \ diagnostic(bool, ShenandoahAllowMixedAllocs, true, \ "Allow mixing mutator and collector allocations in a single " \ "region") \ \ experimental(uintx, ShenandoahAllocSpikeFactor, 5, \ "The amount of heap space to 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 total heap size.") \ range(0,100) \ \ experimental(uintx, ShenandoahEvacReserve, 5, \ "Maximum amount of free space to reserve for evacuation. " \ "Larger values make GC more aggressive, 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 allocation failures, at expense of smaller csets " \ "on each 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 allocations run out of memory too early.") \ \ diagnostic(bool, ShenandoahAllocationTrace, false, \ "Trace allocation latencies and stalls. Can be expensive when " \ "lots of allocations happen, and may introduce scalability " \ "bottlenecks.") \ \ diagnostic(intx, ShenandoahAllocationStallThreshold, 10000, \ "When allocation tracing is enabled, the allocation stalls " \ "larger than this threshold would be reported as warnings. " \ "Time is in microseconds.") \ \ experimental(uintx, ShenandoahEvacAssist, 10, \ "How many objects to evacuate on WB assist path. " \ "Use zero to disable.") \ \ 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. " \ "Time is in milliseconds.") \ \ experimental(uintx, ShenandoahPacingIdleSlack, 2, \ "Percent of heap counted as non-taxable allocations during idle. "\ "Larger value makes the pacing milder during idle phases, " \ "requiring less rendezvous with control thread. Lower value " \ "makes the pacing control less responsive to out-of-cycle allocs.")\ range(0, 100) \ \ experimental(uintx, ShenandoahPacingCycleSlack, 10, \ "Percent of free space taken as non-taxable allocations during " \ "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.") \ 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, \ "Percent of heap that needs to be free after recovery cycles, " \ "either Degenerated or Full GC. If this much space is not " \ "available, next recovery step would triggered.") \ range(0, 100) \ \ diagnostic(bool, ShenandoahDegeneratedGC, true, \ "Use Degenerated GC as the graceful degradation step. Disabling " \ "this leads to degradation to Full GC") \ \ experimental(uintx, ShenandoahFullGCThreshold, 3, \ "How many back-to-back Degenerated GCs to do before triggering " \ "a Full GC.") \ \ experimental(bool, ShenandoahImplicitGCInvokesConcurrent, false, \ "Should internally-caused GCs invoke concurrent cycles, or go to" \ "stop-the-world (degenerated/full)?") \ \ experimental(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.") \ \ diagnostic(bool, ShenandoahOOMDuringEvacALot, false, \ "Simulate OOM during evacuation frequently.") \ \ diagnostic(bool, ShenandoahAllocFailureALot, false, \ "Make lots of artificial allocation failures.") \ \ diagnostic(bool, ShenandoahTerminationTrace, false, \ "Tracing task termination timings") \ \ develop(bool, ShenandoahVerifyObjectEquals, false, \ "Verify that == and != are not used on oops. Only in fastdebug") \ \ diagnostic(bool, ShenandoahAlwaysPreTouch, false, \ "Pre-touch heap memory, overrides global AlwaysPreTouch") \ \ 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 are processed during one marking step") \ \ experimental(uintx, ShenandoahParallelRegionStride, 1024, \ "How many regions are processed in one stride during parallel " \ "iteration.") \ \ experimental(size_t, ShenandoahSATBBufferSize, 1 * K, \ "Number of entries in an SATB log buffer.") \ range(1, max_uintx) \ \ experimental(uintx, ShenandoahSATBBufferFlushInterval, 100, \ "Forcefully flush non-empty SATB buffers at this interval. " \ "Time is in milliseconds.") \ \ experimental(uint, ShenandoahParallelSafepointThreads, 4, \ "Number of parallel threads used for safepoint prolog/epilog") \ \ experimental(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, ShenandoahKeepAliveBarrier, true, \ "Turn on/off keep alive barriers in Shenandoah") \ \ diagnostic(bool, ShenandoahWriteBarrier, true, \ "Turn on/off write barriers in Shenandoah") \ \ diagnostic(bool, ShenandoahReadBarrier, true, \ "Turn on/off read barriers in Shenandoah") \ \ diagnostic(bool, ShenandoahStoreValEnqueueBarrier, false, \ "Turn on/off enqueuing of oops for storeval barriers") \ \ diagnostic(bool, ShenandoahStoreValReadBarrier, true, \ "Turn on/off store val read barriers in Shenandoah") \ \ diagnostic(bool, ShenandoahCASBarrier, true, \ "Turn on/off CAS barriers in Shenandoah") \ \ diagnostic(bool, ShenandoahAcmpBarrier, true, \ "Turn on/off acmp barriers in Shenandoah") \ \ diagnostic(bool, ShenandoahCloneBarrier, true, \ "Turn on/off clone barriers in Shenandoah") \ \ diagnostic(bool, ShenandoahStoreCheck, false, \ "Emit additional code that checks objects are written to only" \ " in to-space") \ \ experimental(bool, ShenandoahConcurrentScanCodeRoots, true, \ "Scan code roots concurrently, instead of during a pause") \ \ experimental(uintx, ShenandoahCodeRootsStyle, 2, \ "Use this style to scan code cache:" \ " 0 - sequential iterator;" \ " 1 - parallel iterator;" \ " 2 - parallel iterator with cset filters;") \ \ experimental(bool, ShenandoahOptimizeStaticFinals, true, \ "Optimize barriers on static final fields. " \ "Turn it off for maximum compatibility with reflection or JNI " \ "code that manipulates final fields.") \ \ experimental(bool, ShenandoahOptimizeInstanceFinals, false, \ "Optimize barriers on final instance fields." \ "Turn it off for maximum compatibility with reflection or JNI " \ "code that manipulates final fields.") \ \ experimental(bool, ShenandoahOptimizeStableFinals, false, \ "Optimize barriers on stable fields." \ "Turn it off for maximum compatibility with reflection or JNI " \ "code that manipulates final fields.") \ \ diagnostic(bool, ShenandoahDecreaseRegisterPressure, false, \ "Try to reuse after-barrier values to reduce register pressure") \ \ experimental(bool, ShenandoahCommonGCStateLoads, false, \ "Enable commonming for GC state loads in generated code.") \ \ develop(bool, ShenandoahVerifyOptoBarriers, false, \ "Verify no missing barriers in C2") \ \ experimental(bool, ShenandoahDontIncreaseWBFreq, true, \ "Common 2 WriteBarriers or WriteBarrier and a ReadBarrier only " \ "if the resulting WriteBarrier isn't executed more frequently") \ \ experimental(bool, ShenandoahLoopOptsAfterExpansion, true, \ "Attempt more loop opts after write barrier expansion") \ #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP