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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. " \
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);" \
+ " generational - generational concurrent GC") \
\
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. " \
" 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.") \
\
+ product(ccstr, ShenandoahOldGCHeuristics, "adaptive", \
+ "Similar to ShenandoahGCHeuristics, but applied to the old " \
+ "generation. This configuration is only used to trigger old " \
+ "collections and does not change how regions are selected " \
+ "for collection.") \
+ \
product(uintx, ShenandoahUnloadClassesFrequency, 1, EXPERIMENTAL, \
"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.") \
\
"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) \
\
product(uintx, ShenandoahInitFreeThreshold, 70, EXPERIMENTAL, \
"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) \
\
product(uintx, ShenandoahMinFreeThreshold, 10, EXPERIMENTAL, \
! "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) \
\
product(uintx, ShenandoahAllocationThreshold, 0, EXPERIMENTAL, \
"How many new allocations should happen since the last GC cycle " \
"before some heuristics trigger the collection. In percents of " \
"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) \
\
+ product(uintx, ShenandoahOldGarbageThreshold, 25, EXPERIMENTAL, \
+ "How much garbage an old region has to contain before it would " \
+ "be taken for collection.") \
+ range(0,100) \
+ \
product(uintx, ShenandoahInitFreeThreshold, 70, EXPERIMENTAL, \
"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) \
\
product(uintx, ShenandoahMinFreeThreshold, 10, EXPERIMENTAL, \
! "Percentage of free heap memory below which most heuristics " \
! "trigger collection independent of other triggers. Provides " \
! "a safety margin for many heuristics. In percents of (soft) " \
+ "max heap size.") \
range(0,100) \
\
product(uintx, ShenandoahAllocationThreshold, 0, EXPERIMENTAL, \
"How many new allocations should happen since the last GC cycle " \
"before some heuristics trigger the collection. In percents of " \
"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.") \
\
+ product(uintx, ShenandoahGuaranteedOldGCInterval, 10*60*1000, EXPERIMENTAL, \
+ "Run a collection of the old generation at least this often. " \
+ "Heuristics may trigger collections more frequently. Time is in " \
+ "milliseconds. Setting this to 0 disables the feature.") \
+ \
product(bool, ShenandoahAlwaysClearSoftRefs, false, EXPERIMENTAL, \
"Unconditionally clear soft references, instead of using any " \
"other cleanup policy. This minimizes footprint at expense of" \
"more soft reference churn in applications.") \
\
product(int, ShenandoahRegionSamplingRate, 40, EXPERIMENTAL, \
"Sampling rate for heap region sampling. In milliseconds between "\
"the samples. Higher values provide more fidelity, at expense " \
"of more sampling overhead.") \
\
+ product(bool, ShenandoahLogRegionSampling, false, \
+ "Save region sampling stream to ShenandoahRegionSamplingFile") \
+ \
+ product(ccstr, ShenandoahRegionSamplingFile, \
+ "./shenandoahSnapshots_pid%p.log", \
+ "If ShenandoahLogRegionSampling is on, save sampling data stream "\
+ "to this file [default: ./shenandoahSnapshots_pid%p.log] " \
+ "(%p replaced with pid)") \
+ \
product(uintx, ShenandoahControlIntervalMin, 1, EXPERIMENTAL, \
"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.") \
" 4 = previous level, plus all marked objects") \
\
product(bool, ShenandoahElasticTLAB, true, DIAGNOSTIC, \
"Use Elastic TLABs with Shenandoah") \
\
+ product(bool, ShenandoahUsePLAB, true, DIAGNOSTIC, \
+ "Use PLABs for object promotions with Shenandoah, " \
+ "if in generational mode and UseTLAB is also set.") \
+ \
product(uintx, ShenandoahEvacReserve, 5, EXPERIMENTAL, \
"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.") \
"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.") \
\
+ product(double, ShenandoahOldEvacReserve, 5.0, EXPERIMENTAL, \
+ "How much of old generation to withhold from evacuations. " \
+ "Larger values will result in fewer live objects being " \
+ "evacuated in the old generation.") \
+ range(1,100) \
+ \
product(bool, ShenandoahPacing, true, EXPERIMENTAL, \
"Pace application allocations to give GC chance to start " \
"and complete before allocation failure is reached.") \
\
product(uintx, ShenandoahPacingMaxDelay, 10, EXPERIMENTAL, \
product(bool, ShenandoahLoopOptsAfterExpansion, true, DIAGNOSTIC, \
"Attempt more loop opts after barrier expansion.") \
\
product(bool, ShenandoahSelfFixing, true, DIAGNOSTIC, \
"Fix references with load reference barrier. Disabling this " \
! "might degrade performance.")
! // end of GC_SHENANDOAH_FLAGS
#endif // SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
product(bool, ShenandoahLoopOptsAfterExpansion, true, DIAGNOSTIC, \
"Attempt more loop opts after barrier expansion.") \
\
product(bool, ShenandoahSelfFixing, true, DIAGNOSTIC, \
"Fix references with load reference barrier. Disabling this " \
! "might degrade performance.") \
+ \
+ product(uintx, ShenandoahTenuredRegionUsageBias, 192, EXPERIMENTAL, \
+ "The collection set is comprised of heap regions that contain " \
+ "the greatest amount of garbage. " \
+ "For purposes of selecting regions to be included in the " \
+ "collection set, regions that have reached the tenure age will " \
+ "be treated as if their contained garbage is the actual " \
+ "contained garbage multiplied by " \
+ "(ShenandoahTenuredRegionUsageBias / 128 (e.g. 150% for the " \
+ "default value) as many times as the region's age meets or " \
+ "exceeds the tenure age. For example, if tenure age is 7, " \
+ "the region age is 9, ShenandoahTenuredRegionUsageBias is " \
+ "192, and the region is 12.5% garbage, this region " \
+ "will by treated as if its garbage content is " \
+ "1/8 * 27/8 = 42.2% when comparing this region to untenured " \
+ "regions.") \
+ range(128, 256) \
+ \
+ product(bool, ShenandoahPromoteTenuredObjects, true, DIAGNOSTIC, \
+ "Turn on/off evacuating individual tenured young objects " \
+ " to the old generation.") \
+ \
+ product(bool, ShenandoahAllowOldMarkingPreemption, true, DIAGNOSTIC, \
+ "Allow young generation collections to suspend concurrent" \
+ " marking in the old generation.") \
+ \
+ product(uintx, ShenandoahAgingCyclePeriod, 1, EXPERIMENTAL, \
+ "With generational mode, increment the age of objects and" \
+ "regions each time this many young-gen GC cycles are completed.")
+ // end of GC_SHENANDOAH_FLAGS
! // 2^ShenandoahTenuredRegionUsageBiasLogBase2 is 128
+ #define ShenandoahTenuredRegionUsageBiasLogBase2 7
#endif // SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
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