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/*
- * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2016, 2021, Red Hat, Inc. All rights reserved.
+ * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* 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.
product_pd, \
notproduct, \
range, \
constraint) \
\
+ product(uintx, ShenandoahGenerationalHumongousReserve, 0, EXPERIMENTAL, \
+ "(Generational mode only) What percent of the heap should be " \
+ "reserved for humongous objects if possible. Old-generation " \
+ "collections will endeavor to evacuate old-gen regions within " \
+ "this reserved area even if these regions do not contain high " \
+ "percentage of garbage. Setting a larger value will cause " \
+ "more frequent old-gen collections. A smaller value will " \
+ "increase the likelihood that humongous object allocations " \
+ "fail, resulting in stop-the-world full GCs.") \
+ range(0,100) \
+ \
+ product(double, ShenandoahMinOldGenGrowthPercent, 12.5, EXPERIMENTAL, \
+ "(Generational mode only) If the usage within old generation " \
+ "has grown by at least this percent of its live memory size " \
+ "at completion of the most recent old-generation marking " \
+ "effort, heuristics may trigger the start of a new old-gen " \
+ "collection.") \
+ range(0.0,100.0) \
+ \
+ product(uintx, ShenandoahIgnoreOldGrowthBelowPercentage,10, EXPERIMENTAL, \
+ "(Generational mode only) If the total usage of the old " \
+ "generation is smaller than this percent, we do not trigger " \
+ "old gen collections even if old has grown, except when " \
+ "ShenandoahGenerationalDoNotIgnoreGrowthAfterYoungCycles " \
+ "consecutive cycles have been completed following the " \
+ "preceding old-gen collection.") \
+ range(0,100) \
+ \
+ product(uintx, ShenandoahDoNotIgnoreGrowthAfterYoungCycles, \
+ 50, EXPERIMENTAL, \
+ "(Generational mode only) Even if the usage of old generation " \
+ "is below ShenandoahIgnoreOldGrowthBelowPercentage, " \
+ "trigger an old-generation mark if old has grown and this " \
+ "many consecutive young-gen collections have been " \
+ "completed following the preceding old-gen collection.") \
+ \
+ product(bool, ShenandoahGenerationalCensusAtEvac, false, EXPERIMENTAL, \
+ "(Generational mode only) Object age census at evacuation, " \
+ "rather than during marking.") \
+ \
+ product(bool, ShenandoahGenerationalAdaptiveTenuring, true, EXPERIMENTAL, \
+ "(Generational mode only) Dynamically adapt tenuring age.") \
+ \
+ product(bool, ShenandoahGenerationalCensusIgnoreOlderCohorts, true, \
+ EXPERIMENTAL,\
+ "(Generational mode only) Ignore mortality rates older than the " \
+ "oldest cohort under the tenuring age for the last cycle." ) \
+ \
+ product(uintx, ShenandoahGenerationalMinTenuringAge, 1, EXPERIMENTAL, \
+ "(Generational mode only) Floor for adaptive tenuring age. " \
+ "Setting floor and ceiling to the same value fixes the tenuring " \
+ "age; setting both to 1 simulates a poor approximation to " \
+ "AlwaysTenure, and setting both to 16 simulates NeverTenure.") \
+ range(1,16) \
+ \
+ product(uintx, ShenandoahGenerationalMaxTenuringAge, 15, EXPERIMENTAL, \
+ "(Generational mode only) Ceiling for adaptive tenuring age. " \
+ "Setting floor and ceiling to the same value fixes the tenuring " \
+ "age; setting both to 1 simulates a poor approximation to " \
+ "AlwaysTenure, and setting both to 16 simulates NeverTenure.") \
+ range(1,16) \
+ \
+ product(double, ShenandoahGenerationalTenuringMortalityRateThreshold, \
+ 0.1, EXPERIMENTAL, \
+ "(Generational mode only) Cohort mortality rates below this " \
+ "value will be treated as indicative of longevity, leading to " \
+ "tenuring. A lower value delays tenuring, a higher value hastens "\
+ "it. Used only when ShenandoahGenerationalhenAdaptiveTenuring is "\
+ "enabled.") \
+ range(0.001,0.999) \
+ \
+ product(size_t, ShenandoahGenerationalTenuringCohortPopulationThreshold, \
+ 4*K, EXPERIMENTAL, \
+ "(Generational mode only) Cohorts whose population is lower than "\
+ "this value in the previous census are ignored wrt tenuring " \
+ "decisions. Effectively this makes then tenurable as soon as all "\
+ "older cohorts are. Set this value to the largest cohort " \
+ "population volume that you are comfortable ignoring when making "\
+ "tenuring decisions.") \
+ \
product(size_t, ShenandoahRegionSize, 0, EXPERIMENTAL, \
"Static heap region size. Set zero to enable automatic sizing.") \
\
product(size_t, ShenandoahTargetNumRegions, 2048, EXPERIMENTAL, \
"With automatic region sizing, this is the approximate number " \
\
product(size_t, ShenandoahMaxRegionSize, 32 * M, EXPERIMENTAL, \
"With automatic region sizing, the regions would be at most " \
"this large.") \
\
- product(intx, ShenandoahHumongousThreshold, 100, EXPERIMENTAL, \
- "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)") \
+ " 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(uintx, ShenandoahExpeditePromotionsThreshold, 5, EXPERIMENTAL, \
+ "When Shenandoah expects to promote at least this percentage " \
+ "of the young generation, trigger a young collection to " \
+ "expedite these promotions.") \
+ range(0,100) \
+ \
+ product(uintx, ShenandoahExpediteMixedThreshold, 10, EXPERIMENTAL, \
+ "When there are this many old regions waiting to be collected, " \
+ "trigger a mixed collection immediately.") \
+ \
product(uintx, ShenandoahGarbageThreshold, 25, EXPERIMENTAL, \
"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) \
\
+ product(uintx, ShenandoahOldGarbageThreshold, 15, EXPERIMENTAL, \
+ "How much garbage an old region has to contain before it would " \
+ "be taken for collection.") \
+ range(0,100) \
+ \
+ product(uintx, ShenandoahIgnoreGarbageThreshold, 5, EXPERIMENTAL, \
+ "When less than this amount of garbage (as a percentage of " \
+ "region size) exists within a region, the region will not be " \
+ "added to the collection set, even when the heuristic has " \
+ "chosen to aggressively add regions with less than " \
+ "ShenandoahGarbageThreshold amount of garbage into the " \
+ "collection set.") \
+ 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.") \
+ "When less than this amount of memory is free within the" \
+ "heap or generation, trigger a learning cycle if we are " \
+ "in learning mode. Learning mode happens during initialization " \
+ "and following a drastic state change, such as following a " \
+ "degenerated or Full GC cycle. 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.")\
+ "Percentage of free heap memory (or young generation, in " \
+ "generational mode) 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 " \
product(uintx, ShenandoahLearningSteps, 5, EXPERIMENTAL, \
"The number of cycles some heuristics take to collect in order " \
"to learn application and GC performance.") \
range(0,100) \
\
- product(uintx, ShenandoahImmediateThreshold, 90, EXPERIMENTAL, \
+ product(uintx, ShenandoahImmediateThreshold, 70, EXPERIMENTAL, \
"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) \
"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(uintx, ShenandoahGuaranteedYoungGCInterval, 5*60*1000, EXPERIMENTAL, \
+ "Run a collection of the young 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.") \
\
" 2 = previous level, plus all roots; " \
" 3 = previous level, plus all reachable objects; " \
" 4 = previous level, plus all marked objects") \
\
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.") \
+ "How much of (young-generation) heap to reserve for " \
+ "(young-generation) evacuations. Larger values allow GC to " \
+ "evacuate more live objects on every cycle, while leaving " \
+ "less headroom for application to allocate while GC is " \
+ "evacuating and updating references. This parameter is " \
+ "consulted at the end of marking, before selecting the " \
+ "collection set. If available memory at this time is smaller " \
+ "than the indicated reserve, the bound on collection set size is "\
+ "adjusted downward. The size of a generational mixed " \
+ "evacuation collection set (comprised of both young and old " \
+ "regions) is also bounded by this parameter. In percents of " \
+ "total (young-generation) heap size.") \
range(1,100) \
\
product(double, ShenandoahEvacWaste, 1.2, EXPERIMENTAL, \
"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.") \
+ "GC cycle. Smaller values increase the risk of evacuation " \
+ "failures, which will trigger stop-the-world Full GC passes.") \
+ range(1.0,100.0) \
+ \
+ product(double, ShenandoahOldEvacWaste, 1.4, EXPERIMENTAL, \
+ "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. Smaller values increase the risk of evacuation " \
+ "failures, which will trigger stop-the-world Full GC passes.") \
+ range(1.0,100.0) \
+ \
+ product(double, ShenandoahPromoEvacWaste, 1.2, EXPERIMENTAL, \
+ "How much waste promotions produce within the reserved space. " \
+ "Larger values make evacuations more resilient against " \
+ "evacuation conflicts, at expense of promoting less on each " \
+ "GC cycle. Smaller values increase the risk of evacuation " \
+ "failures, which will trigger stop-the-world Full GC passes.") \
range(1.0,100.0) \
\
product(bool, ShenandoahEvacReserveOverflow, true, EXPERIMENTAL, \
"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(uintx, ShenandoahOldEvacRatioPercent, 75, EXPERIMENTAL, \
+ "The maximum proportion of evacuation from old-gen memory, " \
+ "expressed as a percentage. The default value 75 denotes that no" \
+ "more than 75% of the collection set evacuation workload may be " \
+ "towards evacuation of old-gen heap regions. This limits both the"\
+ "promotion of aged regions and the compaction of existing old " \
+ "regions. A value of 75 denotes that the total evacuation work" \
+ "may increase to up to four times the young gen evacuation work." \
+ "A larger value allows quicker promotion and allows" \
+ "a smaller number of mixed evacuations to process " \
+ "the entire list of old-gen collection candidates at the cost " \
+ "of an increased disruption of the normal cadence of young-gen " \
+ "collections. A value of 100 allows a mixed evacuation to " \
+ "focus entirely on old-gen memory, allowing no young-gen " \
+ "regions to be collected, likely resulting in subsequent " \
+ "allocation failures because the allocation pool is not " \
+ "replenished. A value of 0 allows a mixed evacuation to" \
+ "focus entirely on young-gen memory, allowing no old-gen " \
+ "regions to be collected, likely resulting in subsequent " \
+ "promotion failures and triggering of stop-the-world full GC " \
+ "events.") \
+ range(0,100) \
+ \
+ product(uintx, ShenandoahMinYoungPercentage, 20, EXPERIMENTAL, \
+ "The minimum percentage of the heap to use for the young " \
+ "generation. Heuristics will not adjust the young generation " \
+ "to be less than this.") \
+ range(0, 100) \
+ \
+ product(uintx, ShenandoahMaxYoungPercentage, 100, EXPERIMENTAL, \
+ "The maximum percentage of the heap to use for the young " \
+ "generation. Heuristics will not adjust the young generation " \
+ "to be more than this.") \
+ range(0, 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(uintx, ShenandoahFullGCThreshold, 3, EXPERIMENTAL, \
"How many back-to-back Degenerated GCs should happen before " \
"going to a Full GC.") \
\
+ product(uintx, ShenandoahNoProgressThreshold, 5, EXPERIMENTAL, \
+ "After this number of consecutive Full GCs fail to make " \
+ "progress, Shenandoah will raise out of memory errors. Note " \
+ "that progress is determined by ShenandoahCriticalFreeThreshold") \
+ \
product(bool, ShenandoahImplicitGCInvokesConcurrent, false, EXPERIMENTAL, \
"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.") \
"Testing: simulate OOM during evacuation.") \
\
product(bool, ShenandoahAllocFailureALot, false, DIAGNOSTIC, \
"Testing: make lots of artificial allocation failures.") \
\
+ product(uintx, ShenandoahCoalesceChance, 0, DIAGNOSTIC, \
+ "Testing: Abandon remaining mixed collections with this " \
+ "likelihood. Following each mixed collection, abandon all " \
+ "remaining mixed collection candidate regions with likelihood " \
+ "ShenandoahCoalesceChance. Abandoning a mixed collection will " \
+ "cause the old regions to be made parsable, rather than being " \
+ "evacuated.") \
+ range(0, 100) \
+ \
product(intx, ShenandoahMarkScanPrefetch, 32, EXPERIMENTAL, \
"How many objects to prefetch ahead when traversing mark bitmaps."\
"Set to 0 to disable prefetching.") \
range(0, 256) \
\
product(uintx, ShenandoahMarkLoopStride, 1000, EXPERIMENTAL, \
"How many items to process during one marking iteration before " \
"checking for cancellation, yielding, etc. Larger values improve "\
"marking performance at expense of responsiveness.") \
\
- product(uintx, ShenandoahParallelRegionStride, 1024, EXPERIMENTAL, \
+ product(uintx, ShenandoahParallelRegionStride, 0, EXPERIMENTAL, \
"How many regions to process at once during parallel region " \
- "iteration. Affects heaps with lots of regions.") \
+ "iteration. Affects heaps with lots of regions. " \
+ "Set to 0 to let Shenandoah to decide the best value.") \
\
product(size_t, ShenandoahSATBBufferSize, 1 * K, EXPERIMENTAL, \
"Number of entries in an SATB log buffer.") \
range(1, max_uintx) \
\
"Turn on/off SATB barriers in Shenandoah") \
\
product(bool, ShenandoahIUBarrier, false, DIAGNOSTIC, \
"Turn on/off I-U barriers barriers in Shenandoah") \
\
+ product(bool, ShenandoahCardBarrier, false, DIAGNOSTIC, \
+ "Turn on/off card-marking post-write barrier in Shenandoah: " \
+ " true when ShenandoahGCMode is generational, false otherwise") \
+ \
product(bool, ShenandoahCASBarrier, true, DIAGNOSTIC, \
"Turn on/off CAS barriers in Shenandoah") \
\
product(bool, ShenandoahCloneBarrier, true, DIAGNOSTIC, \
"Turn on/off clone barriers in Shenandoah") \
"Turn on/off stack watermark barriers in Shenandoah") \
\
develop(bool, ShenandoahVerifyOptoBarriers, trueInDebug, \
"Verify no missing barriers in C2.") \
\
-
- // end of GC_SHENANDOAH_FLAGS
+ product(uintx, ShenandoahOldCompactionReserve, 8, EXPERIMENTAL, \
+ "During generational GC, prevent promotions from filling " \
+ "this number of heap regions. These regions are reserved " \
+ "for the purpose of supporting compaction of old-gen " \
+ "memory. Otherwise, old-gen memory cannot be compacted.") \
+ range(0, 128) \
+ \
+ 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.") \
+ \
+ notproduct(bool, ShenandoahEnableCardStats, false, \
+ "Enable statistics collection related to clean & dirty cards") \
+ \
+ notproduct(int, ShenandoahCardStatsLogInterval, 50, \
+ "Log cumulative card stats every so many remembered set or " \
+ "update refs scans") \
+ \
+ product(uintx, ShenandoahMinimumOldTimeMs, 100, EXPERIMENTAL, \
+ "Minimum amount of time in milliseconds to run old collections " \
+ "before a young collection is allowed to run. This is intended " \
+ "to prevent starvation of the old collector. Setting this to " \
+ "0 will allow back to back young collections to run during old " \
+ "collections.") \
+ // end of GC_SHENANDOAH_FLAGS
#endif // SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
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