1 /*
2 * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2016, 2021, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
27 #define SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
28
29 #define GC_SHENANDOAH_FLAGS(develop, \
30 develop_pd, \
31 product, \
32 product_pd, \
33 notproduct, \
34 range, \
35 constraint) \
36 \
37 product(size_t, ShenandoahRegionSize, 0, EXPERIMENTAL, \
38 "Static heap region size. Set zero to enable automatic sizing.") \
39 \
40 product(size_t, ShenandoahTargetNumRegions, 2048, EXPERIMENTAL, \
41 "With automatic region sizing, this is the approximate number " \
42 "of regions that would be used, within min/max region size " \
43 "limits.") \
44 \
45 product(size_t, ShenandoahMinRegionSize, 256 * K, EXPERIMENTAL, \
46 "With automatic region sizing, the regions would be at least " \
47 "this large.") \
48 \
49 product(size_t, ShenandoahMaxRegionSize, 32 * M, EXPERIMENTAL, \
50 "With automatic region sizing, the regions would be at most " \
51 "this large.") \
52 \
53 product(intx, ShenandoahHumongousThreshold, 100, EXPERIMENTAL, \
54 "Humongous objects are allocated in separate regions. " \
55 "This setting defines how large the object should be to be " \
56 "deemed humongous. Value is in percents of heap region size. " \
57 "This also caps the maximum TLAB size.") \
58 range(1, 100) \
59 \
60 product(ccstr, ShenandoahGCMode, "satb", \
61 "GC mode to use. Among other things, this defines which " \
62 "barriers are in in use. Possible values are:" \
63 " satb - snapshot-at-the-beginning concurrent GC (three pass mark-evac-update);" \
64 " iu - incremental-update concurrent GC (three pass mark-evac-update);" \
65 " passive - stop the world GC only (either degenerated or full)") \
66 \
67 product(ccstr, ShenandoahGCHeuristics, "adaptive", \
68 "GC heuristics to use. This fine-tunes the GC mode selected, " \
69 "by choosing when to start the GC, how much to process on each " \
70 "cycle, and what other features to automatically enable. " \
71 "Possible values are:" \
72 " adaptive - adapt to maintain the given amount of free heap " \
73 "at all times, even during the GC cycle;" \
74 " static - trigger GC when free heap falls below the threshold;" \
75 " aggressive - run GC continuously, try to evacuate everything;" \
76 " compact - run GC more frequently and with deeper targets to " \
77 "free up more memory.") \
78 \
79 product(uintx, ShenandoahGarbageThreshold, 25, EXPERIMENTAL, \
80 "How much garbage a region has to contain before it would be " \
81 "taken for collection. This a guideline only, as GC heuristics " \
82 "may select the region for collection even if it has little " \
83 "garbage. This also affects how much internal fragmentation the " \
84 "collector accepts. In percents of heap region size.") \
85 range(0,100) \
86 \
87 product(uintx, ShenandoahInitFreeThreshold, 70, EXPERIMENTAL, \
88 "How much heap should be free before some heuristics trigger the "\
89 "initial (learning) cycles. Affects cycle frequency on startup " \
90 "and after drastic state changes, e.g. after degenerated/full " \
91 "GC cycles. In percents of (soft) max heap size.") \
92 range(0,100) \
93 \
94 product(uintx, ShenandoahMinFreeThreshold, 10, EXPERIMENTAL, \
95 "How much heap should be free before most heuristics trigger the "\
96 "collection, even without other triggers. Provides the safety " \
97 "margin for many heuristics. In percents of (soft) max heap size.")\
98 range(0,100) \
99 \
100 product(uintx, ShenandoahAllocationThreshold, 0, EXPERIMENTAL, \
101 "How many new allocations should happen since the last GC cycle " \
102 "before some heuristics trigger the collection. In percents of " \
103 "(soft) max heap size. Set to zero to effectively disable.") \
104 range(0,100) \
105 \
106 product(uintx, ShenandoahAllocSpikeFactor, 5, EXPERIMENTAL, \
107 "How much of heap should some heuristics reserve for absorbing " \
108 "the allocation spikes. Larger value wastes more memory in " \
109 "non-emergency cases, but provides more safety in emergency " \
110 "cases. In percents of (soft) max heap size.") \
111 range(0,100) \
112 \
113 product(uintx, ShenandoahLearningSteps, 5, EXPERIMENTAL, \
114 "The number of cycles some heuristics take to collect in order " \
115 "to learn application and GC performance.") \
116 range(0,100) \
117 \
118 product(uintx, ShenandoahImmediateThreshold, 90, EXPERIMENTAL, \
119 "The cycle may shortcut when enough garbage can be reclaimed " \
120 "from the immediate garbage (completely garbage regions). " \
121 "In percents of total garbage found. Setting this threshold " \
122 "to 100 effectively disables the shortcut.") \
123 range(0,100) \
124 \
125 product(uintx, ShenandoahAdaptiveSampleFrequencyHz, 10, EXPERIMENTAL, \
126 "The number of times per second to update the allocation rate " \
127 "moving average.") \
128 \
129 product(uintx, ShenandoahAdaptiveSampleSizeSeconds, 10, EXPERIMENTAL, \
130 "The size of the moving window over which the average " \
131 "allocation rate is maintained. The total number of samples " \
132 "is the product of this number and the sample frequency.") \
133 \
134 product(double, ShenandoahAdaptiveInitialConfidence, 1.8, EXPERIMENTAL, \
135 "The number of standard deviations used to determine an initial " \
136 "margin of error for the average cycle time and average " \
137 "allocation rate. Increasing this value will cause the " \
138 "heuristic to initiate more concurrent cycles." ) \
140 product(double, ShenandoahAdaptiveInitialSpikeThreshold, 1.8, EXPERIMENTAL, \
141 "If the most recently sampled allocation rate is more than " \
142 "this many standard deviations away from the moving average, " \
143 "then a cycle is initiated. This value controls how sensitive " \
144 "the heuristic is to allocation spikes. Decreasing this number " \
145 "increases the sensitivity. ") \
146 \
147 product(double, ShenandoahAdaptiveDecayFactor, 0.5, EXPERIMENTAL, \
148 "The decay factor (alpha) used for values in the weighted " \
149 "moving average of cycle time and allocation rate. " \
150 "Larger values give more weight to recent values.") \
151 range(0,1.0) \
152 \
153 product(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, EXPERIMENTAL, \
154 "Many heuristics would guarantee a concurrent GC cycle at " \
155 "least with this interval. This is useful when large idle " \
156 "intervals are present, where GC can run without stealing " \
157 "time from active application. Time is in milliseconds. " \
158 "Setting this to 0 disables the feature.") \
159 \
160 product(bool, ShenandoahAlwaysClearSoftRefs, false, EXPERIMENTAL, \
161 "Unconditionally clear soft references, instead of using any " \
162 "other cleanup policy. This minimizes footprint at expense of" \
163 "more soft reference churn in applications.") \
164 \
165 product(bool, ShenandoahUncommit, true, EXPERIMENTAL, \
166 "Allow to uncommit memory under unused regions and metadata. " \
167 "This optimizes footprint at expense of allocation latency in " \
168 "regions that require committing back. Uncommits would be " \
169 "disabled by some heuristics, or with static heap size.") \
170 \
171 product(uintx, ShenandoahUncommitDelay, 5*60*1000, EXPERIMENTAL, \
172 "Uncommit memory for regions that were not used for more than " \
173 "this time. First use after that would incur allocation stalls. " \
174 "Actively used regions would never be uncommitted, because they " \
175 "do not become unused longer than this delay. Time is in " \
176 "milliseconds. Setting this delay to 0 effectively uncommits " \
177 "regions almost immediately after they become unused.") \
178 \
179 product(bool, ShenandoahRegionSampling, false, EXPERIMENTAL, \
199 product(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, EXPERIMENTAL, \
200 "The time period for one step in control loop interval " \
201 "adjustment. Lower values make adjustments faster, at the " \
202 "expense of higher perf overhead. Time is in milliseconds.") \
203 \
204 product(bool, ShenandoahVerify, false, DIAGNOSTIC, \
205 "Enable internal verification. This would catch many GC bugs, " \
206 "but it would also stall the collector during the verification, " \
207 "which prolongs the pauses and might hide other bugs.") \
208 \
209 product(intx, ShenandoahVerifyLevel, 4, DIAGNOSTIC, \
210 "Verification level, higher levels check more, taking more time. "\
211 "Accepted values are:" \
212 " 0 = basic heap checks; " \
213 " 1 = previous level, plus basic region checks; " \
214 " 2 = previous level, plus all roots; " \
215 " 3 = previous level, plus all reachable objects; " \
216 " 4 = previous level, plus all marked objects") \
217 \
218 product(uintx, ShenandoahEvacReserve, 5, EXPERIMENTAL, \
219 "How much of heap to reserve for evacuations. Larger values make "\
220 "GC evacuate more live objects on every cycle, while leaving " \
221 "less headroom for application to allocate in. In percents of " \
222 "total heap size.") \
223 range(1,100) \
224 \
225 product(double, ShenandoahEvacWaste, 1.2, EXPERIMENTAL, \
226 "How much waste evacuations produce within the reserved space. " \
227 "Larger values make evacuations more resilient against " \
228 "evacuation conflicts, at expense of evacuating less on each " \
229 "GC cycle.") \
230 range(1.0,100.0) \
231 \
232 product(bool, ShenandoahEvacReserveOverflow, true, EXPERIMENTAL, \
233 "Allow evacuations to overflow the reserved space. Enabling it " \
234 "will make evacuations more resilient when evacuation " \
235 "reserve/waste is incorrect, at the risk that application " \
236 "runs out of memory too early.") \
237 \
238 product(bool, ShenandoahPacing, true, EXPERIMENTAL, \
239 "Pace application allocations to give GC chance to start " \
240 "and complete before allocation failure is reached.") \
241 \
242 product(uintx, ShenandoahPacingMaxDelay, 10, EXPERIMENTAL, \
243 "Max delay for pacing application allocations. Larger values " \
244 "provide more resilience against out of memory, at expense at " \
245 "hiding the GC latencies in the allocation path. Time is in " \
246 "milliseconds. Setting it to arbitrarily large value makes " \
247 "GC effectively stall the threads indefinitely instead of going " \
248 "to degenerated or Full GC.") \
249 \
250 product(uintx, ShenandoahPacingIdleSlack, 2, EXPERIMENTAL, \
251 "How much of heap counted as non-taxable allocations during idle "\
252 "phases. Larger value makes the pacing milder when collector is " \
253 "idle, requiring less rendezvous with control thread. Lower " \
254 "value makes the pacing control less responsive to out-of-cycle " \
255 "allocs. In percent of total heap size.") \
256 range(0, 100) \
257 \
269 "the beginning of it.") \
270 range(1.0, 100.0) \
271 \
272 product(uintx, ShenandoahCriticalFreeThreshold, 1, EXPERIMENTAL, \
273 "How much of the heap needs to be free after recovery cycles, " \
274 "either Degenerated or Full GC to be claimed successful. If this "\
275 "much space is not available, next recovery step would be " \
276 "triggered.") \
277 range(0, 100) \
278 \
279 product(bool, ShenandoahDegeneratedGC, true, DIAGNOSTIC, \
280 "Enable Degenerated GC as the graceful degradation step. " \
281 "Disabling this option leads to degradation to Full GC instead. " \
282 "When running in passive mode, this can be toggled to measure " \
283 "either Degenerated GC or Full GC costs.") \
284 \
285 product(uintx, ShenandoahFullGCThreshold, 3, EXPERIMENTAL, \
286 "How many back-to-back Degenerated GCs should happen before " \
287 "going to a Full GC.") \
288 \
289 product(bool, ShenandoahImplicitGCInvokesConcurrent, false, EXPERIMENTAL, \
290 "Should internally-caused GC requests invoke concurrent cycles, " \
291 "should they do the stop-the-world (Degenerated / Full GC)? " \
292 "Many heuristics automatically enable this. This option is " \
293 "similar to global ExplicitGCInvokesConcurrent.") \
294 \
295 product(bool, ShenandoahHumongousMoves, true, DIAGNOSTIC, \
296 "Allow moving humongous regions. This makes GC more resistant " \
297 "to external fragmentation that may otherwise fail other " \
298 "humongous allocations, at the expense of higher GC copying " \
299 "costs. Currently affects stop-the-world (Full) cycle only.") \
300 \
301 product(bool, ShenandoahOOMDuringEvacALot, false, DIAGNOSTIC, \
302 "Testing: simulate OOM during evacuation.") \
303 \
304 product(bool, ShenandoahAllocFailureALot, false, DIAGNOSTIC, \
305 "Testing: make lots of artificial allocation failures.") \
306 \
307 product(intx, ShenandoahMarkScanPrefetch, 32, EXPERIMENTAL, \
308 "How many objects to prefetch ahead when traversing mark bitmaps."\
309 "Set to 0 to disable prefetching.") \
310 range(0, 256) \
311 \
312 product(uintx, ShenandoahMarkLoopStride, 1000, EXPERIMENTAL, \
313 "How many items to process during one marking iteration before " \
314 "checking for cancellation, yielding, etc. Larger values improve "\
315 "marking performance at expense of responsiveness.") \
316 \
317 product(uintx, ShenandoahParallelRegionStride, 0, EXPERIMENTAL, \
318 "How many regions to process at once during parallel region " \
319 "iteration. Affects heaps with lots of regions. " \
320 "Set to 0 to let Shenandoah to decide the best value.") \
321 \
322 product(size_t, ShenandoahSATBBufferSize, 1 * K, EXPERIMENTAL, \
323 "Number of entries in an SATB log buffer.") \
324 range(1, max_uintx) \
325 \
326 product(uintx, ShenandoahMaxSATBBufferFlushes, 5, EXPERIMENTAL, \
327 "How many times to maximum attempt to flush SATB buffers at the " \
328 "end of concurrent marking.") \
329 \
330 product(bool, ShenandoahSATBBarrier, true, DIAGNOSTIC, \
331 "Turn on/off SATB barriers in Shenandoah") \
332 \
333 product(bool, ShenandoahIUBarrier, false, DIAGNOSTIC, \
334 "Turn on/off I-U barriers barriers in Shenandoah") \
335 \
336 product(bool, ShenandoahCASBarrier, true, DIAGNOSTIC, \
337 "Turn on/off CAS barriers in Shenandoah") \
338 \
339 product(bool, ShenandoahCloneBarrier, true, DIAGNOSTIC, \
340 "Turn on/off clone barriers in Shenandoah") \
341 \
342 product(bool, ShenandoahLoadRefBarrier, true, DIAGNOSTIC, \
343 "Turn on/off load-reference barriers in Shenandoah") \
344 \
345 product(bool, ShenandoahStackWatermarkBarrier, true, DIAGNOSTIC, \
346 "Turn on/off stack watermark barriers in Shenandoah") \
347 \
348 develop(bool, ShenandoahVerifyOptoBarriers, trueInDebug, \
349 "Verify no missing barriers in C2.") \
350 \
351
352 // end of GC_SHENANDOAH_FLAGS
353
354 #endif // SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
|
1 /*
2 * Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2016, 2021, Red Hat, Inc. All rights reserved.
4 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
28 #define SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
29
30 #define GC_SHENANDOAH_FLAGS(develop, \
31 develop_pd, \
32 product, \
33 product_pd, \
34 notproduct, \
35 range, \
36 constraint) \
37 \
38 product(uintx, ShenandoahGenerationalHumongousReserve, 0, EXPERIMENTAL, \
39 "(Generational mode only) What percent of the heap should be " \
40 "reserved for humongous objects if possible. Old-generation " \
41 "collections will endeavor to evacuate old-gen regions within " \
42 "this reserved area even if these regions do not contain high " \
43 "percentage of garbage. Setting a larger value will cause " \
44 "more frequent old-gen collections. A smaller value will " \
45 "increase the likelihood that humongous object allocations " \
46 "fail, resulting in stop-the-world full GCs.") \
47 range(0,100) \
48 \
49 product(double, ShenandoahMinOldGenGrowthPercent, 12.5, EXPERIMENTAL, \
50 "(Generational mode only) If the usage within old generation " \
51 "has grown by at least this percent of its live memory size " \
52 "at completion of the most recent old-generation marking " \
53 "effort, heuristics may trigger the start of a new old-gen " \
54 "collection.") \
55 range(0.0,100.0) \
56 \
57 product(uintx, ShenandoahIgnoreOldGrowthBelowPercentage,10, EXPERIMENTAL, \
58 "(Generational mode only) If the total usage of the old " \
59 "generation is smaller than this percent, we do not trigger " \
60 "old gen collections even if old has grown, except when " \
61 "ShenandoahGenerationalDoNotIgnoreGrowthAfterYoungCycles " \
62 "consecutive cycles have been completed following the " \
63 "preceding old-gen collection.") \
64 range(0,100) \
65 \
66 product(uintx, ShenandoahDoNotIgnoreGrowthAfterYoungCycles, \
67 50, EXPERIMENTAL, \
68 "(Generational mode only) Even if the usage of old generation " \
69 "is below ShenandoahIgnoreOldGrowthBelowPercentage, " \
70 "trigger an old-generation mark if old has grown and this " \
71 "many consecutive young-gen collections have been " \
72 "completed following the preceding old-gen collection.") \
73 \
74 product(bool, ShenandoahGenerationalCensusAtEvac, false, EXPERIMENTAL, \
75 "(Generational mode only) Object age census at evacuation, " \
76 "rather than during marking.") \
77 \
78 product(bool, ShenandoahGenerationalAdaptiveTenuring, true, EXPERIMENTAL, \
79 "(Generational mode only) Dynamically adapt tenuring age.") \
80 \
81 product(bool, ShenandoahGenerationalCensusIgnoreOlderCohorts, true, \
82 EXPERIMENTAL,\
83 "(Generational mode only) Ignore mortality rates older than the " \
84 "oldest cohort under the tenuring age for the last cycle." ) \
85 \
86 product(uintx, ShenandoahGenerationalMinTenuringAge, 1, EXPERIMENTAL, \
87 "(Generational mode only) Floor for adaptive tenuring age. " \
88 "Setting floor and ceiling to the same value fixes the tenuring " \
89 "age; setting both to 1 simulates a poor approximation to " \
90 "AlwaysTenure, and setting both to 16 simulates NeverTenure.") \
91 range(1,16) \
92 \
93 product(uintx, ShenandoahGenerationalMaxTenuringAge, 15, EXPERIMENTAL, \
94 "(Generational mode only) Ceiling for adaptive tenuring age. " \
95 "Setting floor and ceiling to the same value fixes the tenuring " \
96 "age; setting both to 1 simulates a poor approximation to " \
97 "AlwaysTenure, and setting both to 16 simulates NeverTenure.") \
98 range(1,16) \
99 \
100 product(double, ShenandoahGenerationalTenuringMortalityRateThreshold, \
101 0.1, EXPERIMENTAL, \
102 "(Generational mode only) Cohort mortality rates below this " \
103 "value will be treated as indicative of longevity, leading to " \
104 "tenuring. A lower value delays tenuring, a higher value hastens "\
105 "it. Used only when ShenandoahGenerationalhenAdaptiveTenuring is "\
106 "enabled.") \
107 range(0.001,0.999) \
108 \
109 product(size_t, ShenandoahGenerationalTenuringCohortPopulationThreshold, \
110 4*K, EXPERIMENTAL, \
111 "(Generational mode only) Cohorts whose population is lower than "\
112 "this value in the previous census are ignored wrt tenuring " \
113 "decisions. Effectively this makes then tenurable as soon as all "\
114 "older cohorts are. Set this value to the largest cohort " \
115 "population volume that you are comfortable ignoring when making "\
116 "tenuring decisions.") \
117 \
118 product(size_t, ShenandoahRegionSize, 0, EXPERIMENTAL, \
119 "Static heap region size. Set zero to enable automatic sizing.") \
120 \
121 product(size_t, ShenandoahTargetNumRegions, 2048, EXPERIMENTAL, \
122 "With automatic region sizing, this is the approximate number " \
123 "of regions that would be used, within min/max region size " \
124 "limits.") \
125 \
126 product(size_t, ShenandoahMinRegionSize, 256 * K, EXPERIMENTAL, \
127 "With automatic region sizing, the regions would be at least " \
128 "this large.") \
129 \
130 product(size_t, ShenandoahMaxRegionSize, 32 * M, EXPERIMENTAL, \
131 "With automatic region sizing, the regions would be at most " \
132 "this large.") \
133 \
134 product(ccstr, ShenandoahGCMode, "satb", \
135 "GC mode to use. Among other things, this defines which " \
136 "barriers are in in use. Possible values are:" \
137 " satb - snapshot-at-the-beginning concurrent GC (three pass mark-evac-update);" \
138 " iu - incremental-update concurrent GC (three pass mark-evac-update);" \
139 " passive - stop the world GC only (either degenerated or full);" \
140 " generational - generational concurrent GC") \
141 \
142 product(ccstr, ShenandoahGCHeuristics, "adaptive", \
143 "GC heuristics to use. This fine-tunes the GC mode selected, " \
144 "by choosing when to start the GC, how much to process on each " \
145 "cycle, and what other features to automatically enable. " \
146 "Possible values are:" \
147 " adaptive - adapt to maintain the given amount of free heap " \
148 "at all times, even during the GC cycle;" \
149 " static - trigger GC when free heap falls below the threshold;" \
150 " aggressive - run GC continuously, try to evacuate everything;" \
151 " compact - run GC more frequently and with deeper targets to " \
152 "free up more memory.") \
153 \
154 product(uintx, ShenandoahExpeditePromotionsThreshold, 5, EXPERIMENTAL, \
155 "When Shenandoah expects to promote at least this percentage " \
156 "of the young generation, trigger a young collection to " \
157 "expedite these promotions.") \
158 range(0,100) \
159 \
160 product(uintx, ShenandoahExpediteMixedThreshold, 10, EXPERIMENTAL, \
161 "When there are this many old regions waiting to be collected, " \
162 "trigger a mixed collection immediately.") \
163 \
164 product(uintx, ShenandoahGarbageThreshold, 25, EXPERIMENTAL, \
165 "How much garbage a region has to contain before it would be " \
166 "taken for collection. This a guideline only, as GC heuristics " \
167 "may select the region for collection even if it has little " \
168 "garbage. This also affects how much internal fragmentation the " \
169 "collector accepts. In percents of heap region size.") \
170 range(0,100) \
171 \
172 product(uintx, ShenandoahOldGarbageThreshold, 15, EXPERIMENTAL, \
173 "How much garbage an old region has to contain before it would " \
174 "be taken for collection.") \
175 range(0,100) \
176 \
177 product(uintx, ShenandoahIgnoreGarbageThreshold, 5, EXPERIMENTAL, \
178 "When less than this amount of garbage (as a percentage of " \
179 "region size) exists within a region, the region will not be " \
180 "added to the collection set, even when the heuristic has " \
181 "chosen to aggressively add regions with less than " \
182 "ShenandoahGarbageThreshold amount of garbage into the " \
183 "collection set.") \
184 range(0,100) \
185 \
186 product(uintx, ShenandoahInitFreeThreshold, 70, EXPERIMENTAL, \
187 "When less than this amount of memory is free within the" \
188 "heap or generation, trigger a learning cycle if we are " \
189 "in learning mode. Learning mode happens during initialization " \
190 "and following a drastic state change, such as following a " \
191 "degenerated or Full GC cycle. In percents of soft max " \
192 "heap size.") \
193 range(0,100) \
194 \
195 product(uintx, ShenandoahMinFreeThreshold, 10, EXPERIMENTAL, \
196 "Percentage of free heap memory (or young generation, in " \
197 "generational mode) below which most heuristics trigger " \
198 "collection independent of other triggers. Provides a safety " \
199 "margin for many heuristics. In percents of (soft) max heap " \
200 "size.") \
201 range(0,100) \
202 \
203 product(uintx, ShenandoahAllocationThreshold, 0, EXPERIMENTAL, \
204 "How many new allocations should happen since the last GC cycle " \
205 "before some heuristics trigger the collection. In percents of " \
206 "(soft) max heap size. Set to zero to effectively disable.") \
207 range(0,100) \
208 \
209 product(uintx, ShenandoahAllocSpikeFactor, 5, EXPERIMENTAL, \
210 "How much of heap should some heuristics reserve for absorbing " \
211 "the allocation spikes. Larger value wastes more memory in " \
212 "non-emergency cases, but provides more safety in emergency " \
213 "cases. In percents of (soft) max heap size.") \
214 range(0,100) \
215 \
216 product(uintx, ShenandoahLearningSteps, 5, EXPERIMENTAL, \
217 "The number of cycles some heuristics take to collect in order " \
218 "to learn application and GC performance.") \
219 range(0,100) \
220 \
221 product(uintx, ShenandoahImmediateThreshold, 70, EXPERIMENTAL, \
222 "The cycle may shortcut when enough garbage can be reclaimed " \
223 "from the immediate garbage (completely garbage regions). " \
224 "In percents of total garbage found. Setting this threshold " \
225 "to 100 effectively disables the shortcut.") \
226 range(0,100) \
227 \
228 product(uintx, ShenandoahAdaptiveSampleFrequencyHz, 10, EXPERIMENTAL, \
229 "The number of times per second to update the allocation rate " \
230 "moving average.") \
231 \
232 product(uintx, ShenandoahAdaptiveSampleSizeSeconds, 10, EXPERIMENTAL, \
233 "The size of the moving window over which the average " \
234 "allocation rate is maintained. The total number of samples " \
235 "is the product of this number and the sample frequency.") \
236 \
237 product(double, ShenandoahAdaptiveInitialConfidence, 1.8, EXPERIMENTAL, \
238 "The number of standard deviations used to determine an initial " \
239 "margin of error for the average cycle time and average " \
240 "allocation rate. Increasing this value will cause the " \
241 "heuristic to initiate more concurrent cycles." ) \
243 product(double, ShenandoahAdaptiveInitialSpikeThreshold, 1.8, EXPERIMENTAL, \
244 "If the most recently sampled allocation rate is more than " \
245 "this many standard deviations away from the moving average, " \
246 "then a cycle is initiated. This value controls how sensitive " \
247 "the heuristic is to allocation spikes. Decreasing this number " \
248 "increases the sensitivity. ") \
249 \
250 product(double, ShenandoahAdaptiveDecayFactor, 0.5, EXPERIMENTAL, \
251 "The decay factor (alpha) used for values in the weighted " \
252 "moving average of cycle time and allocation rate. " \
253 "Larger values give more weight to recent values.") \
254 range(0,1.0) \
255 \
256 product(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, EXPERIMENTAL, \
257 "Many heuristics would guarantee a concurrent GC cycle at " \
258 "least with this interval. This is useful when large idle " \
259 "intervals are present, where GC can run without stealing " \
260 "time from active application. Time is in milliseconds. " \
261 "Setting this to 0 disables the feature.") \
262 \
263 product(uintx, ShenandoahGuaranteedOldGCInterval, 10*60*1000, EXPERIMENTAL, \
264 "Run a collection of the old generation at least this often. " \
265 "Heuristics may trigger collections more frequently. Time is in " \
266 "milliseconds. Setting this to 0 disables the feature.") \
267 \
268 product(uintx, ShenandoahGuaranteedYoungGCInterval, 5*60*1000, EXPERIMENTAL, \
269 "Run a collection of the young generation at least this often. " \
270 "Heuristics may trigger collections more frequently. Time is in " \
271 "milliseconds. Setting this to 0 disables the feature.") \
272 \
273 product(bool, ShenandoahAlwaysClearSoftRefs, false, EXPERIMENTAL, \
274 "Unconditionally clear soft references, instead of using any " \
275 "other cleanup policy. This minimizes footprint at expense of" \
276 "more soft reference churn in applications.") \
277 \
278 product(bool, ShenandoahUncommit, true, EXPERIMENTAL, \
279 "Allow to uncommit memory under unused regions and metadata. " \
280 "This optimizes footprint at expense of allocation latency in " \
281 "regions that require committing back. Uncommits would be " \
282 "disabled by some heuristics, or with static heap size.") \
283 \
284 product(uintx, ShenandoahUncommitDelay, 5*60*1000, EXPERIMENTAL, \
285 "Uncommit memory for regions that were not used for more than " \
286 "this time. First use after that would incur allocation stalls. " \
287 "Actively used regions would never be uncommitted, because they " \
288 "do not become unused longer than this delay. Time is in " \
289 "milliseconds. Setting this delay to 0 effectively uncommits " \
290 "regions almost immediately after they become unused.") \
291 \
292 product(bool, ShenandoahRegionSampling, false, EXPERIMENTAL, \
312 product(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, EXPERIMENTAL, \
313 "The time period for one step in control loop interval " \
314 "adjustment. Lower values make adjustments faster, at the " \
315 "expense of higher perf overhead. Time is in milliseconds.") \
316 \
317 product(bool, ShenandoahVerify, false, DIAGNOSTIC, \
318 "Enable internal verification. This would catch many GC bugs, " \
319 "but it would also stall the collector during the verification, " \
320 "which prolongs the pauses and might hide other bugs.") \
321 \
322 product(intx, ShenandoahVerifyLevel, 4, DIAGNOSTIC, \
323 "Verification level, higher levels check more, taking more time. "\
324 "Accepted values are:" \
325 " 0 = basic heap checks; " \
326 " 1 = previous level, plus basic region checks; " \
327 " 2 = previous level, plus all roots; " \
328 " 3 = previous level, plus all reachable objects; " \
329 " 4 = previous level, plus all marked objects") \
330 \
331 product(uintx, ShenandoahEvacReserve, 5, EXPERIMENTAL, \
332 "How much of (young-generation) heap to reserve for " \
333 "(young-generation) evacuations. Larger values allow GC to " \
334 "evacuate more live objects on every cycle, while leaving " \
335 "less headroom for application to allocate while GC is " \
336 "evacuating and updating references. This parameter is " \
337 "consulted at the end of marking, before selecting the " \
338 "collection set. If available memory at this time is smaller " \
339 "than the indicated reserve, the bound on collection set size is "\
340 "adjusted downward. The size of a generational mixed " \
341 "evacuation collection set (comprised of both young and old " \
342 "regions) is also bounded by this parameter. In percents of " \
343 "total (young-generation) heap size.") \
344 range(1,100) \
345 \
346 product(double, ShenandoahEvacWaste, 1.2, EXPERIMENTAL, \
347 "How much waste evacuations produce within the reserved space. " \
348 "Larger values make evacuations more resilient against " \
349 "evacuation conflicts, at expense of evacuating less on each " \
350 "GC cycle. Smaller values increase the risk of evacuation " \
351 "failures, which will trigger stop-the-world Full GC passes.") \
352 range(1.0,100.0) \
353 \
354 product(double, ShenandoahOldEvacWaste, 1.4, EXPERIMENTAL, \
355 "How much waste evacuations produce within the reserved space. " \
356 "Larger values make evacuations more resilient against " \
357 "evacuation conflicts, at expense of evacuating less on each " \
358 "GC cycle. Smaller values increase the risk of evacuation " \
359 "failures, which will trigger stop-the-world Full GC passes.") \
360 range(1.0,100.0) \
361 \
362 product(double, ShenandoahPromoEvacWaste, 1.2, EXPERIMENTAL, \
363 "How much waste promotions produce within the reserved space. " \
364 "Larger values make evacuations more resilient against " \
365 "evacuation conflicts, at expense of promoting less on each " \
366 "GC cycle. Smaller values increase the risk of evacuation " \
367 "failures, which will trigger stop-the-world Full GC passes.") \
368 range(1.0,100.0) \
369 \
370 product(bool, ShenandoahEvacReserveOverflow, true, EXPERIMENTAL, \
371 "Allow evacuations to overflow the reserved space. Enabling it " \
372 "will make evacuations more resilient when evacuation " \
373 "reserve/waste is incorrect, at the risk that application " \
374 "runs out of memory too early.") \
375 \
376 product(uintx, ShenandoahOldEvacRatioPercent, 75, EXPERIMENTAL, \
377 "The maximum proportion of evacuation from old-gen memory, " \
378 "expressed as a percentage. The default value 75 denotes that no" \
379 "more than 75% of the collection set evacuation workload may be " \
380 "towards evacuation of old-gen heap regions. This limits both the"\
381 "promotion of aged regions and the compaction of existing old " \
382 "regions. A value of 75 denotes that the total evacuation work" \
383 "may increase to up to four times the young gen evacuation work." \
384 "A larger value allows quicker promotion and allows" \
385 "a smaller number of mixed evacuations to process " \
386 "the entire list of old-gen collection candidates at the cost " \
387 "of an increased disruption of the normal cadence of young-gen " \
388 "collections. A value of 100 allows a mixed evacuation to " \
389 "focus entirely on old-gen memory, allowing no young-gen " \
390 "regions to be collected, likely resulting in subsequent " \
391 "allocation failures because the allocation pool is not " \
392 "replenished. A value of 0 allows a mixed evacuation to" \
393 "focus entirely on young-gen memory, allowing no old-gen " \
394 "regions to be collected, likely resulting in subsequent " \
395 "promotion failures and triggering of stop-the-world full GC " \
396 "events.") \
397 range(0,100) \
398 \
399 product(uintx, ShenandoahMinYoungPercentage, 20, EXPERIMENTAL, \
400 "The minimum percentage of the heap to use for the young " \
401 "generation. Heuristics will not adjust the young generation " \
402 "to be less than this.") \
403 range(0, 100) \
404 \
405 product(uintx, ShenandoahMaxYoungPercentage, 100, EXPERIMENTAL, \
406 "The maximum percentage of the heap to use for the young " \
407 "generation. Heuristics will not adjust the young generation " \
408 "to be more than this.") \
409 range(0, 100) \
410 \
411 product(bool, ShenandoahPacing, true, EXPERIMENTAL, \
412 "Pace application allocations to give GC chance to start " \
413 "and complete before allocation failure is reached.") \
414 \
415 product(uintx, ShenandoahPacingMaxDelay, 10, EXPERIMENTAL, \
416 "Max delay for pacing application allocations. Larger values " \
417 "provide more resilience against out of memory, at expense at " \
418 "hiding the GC latencies in the allocation path. Time is in " \
419 "milliseconds. Setting it to arbitrarily large value makes " \
420 "GC effectively stall the threads indefinitely instead of going " \
421 "to degenerated or Full GC.") \
422 \
423 product(uintx, ShenandoahPacingIdleSlack, 2, EXPERIMENTAL, \
424 "How much of heap counted as non-taxable allocations during idle "\
425 "phases. Larger value makes the pacing milder when collector is " \
426 "idle, requiring less rendezvous with control thread. Lower " \
427 "value makes the pacing control less responsive to out-of-cycle " \
428 "allocs. In percent of total heap size.") \
429 range(0, 100) \
430 \
442 "the beginning of it.") \
443 range(1.0, 100.0) \
444 \
445 product(uintx, ShenandoahCriticalFreeThreshold, 1, EXPERIMENTAL, \
446 "How much of the heap needs to be free after recovery cycles, " \
447 "either Degenerated or Full GC to be claimed successful. If this "\
448 "much space is not available, next recovery step would be " \
449 "triggered.") \
450 range(0, 100) \
451 \
452 product(bool, ShenandoahDegeneratedGC, true, DIAGNOSTIC, \
453 "Enable Degenerated GC as the graceful degradation step. " \
454 "Disabling this option leads to degradation to Full GC instead. " \
455 "When running in passive mode, this can be toggled to measure " \
456 "either Degenerated GC or Full GC costs.") \
457 \
458 product(uintx, ShenandoahFullGCThreshold, 3, EXPERIMENTAL, \
459 "How many back-to-back Degenerated GCs should happen before " \
460 "going to a Full GC.") \
461 \
462 product(uintx, ShenandoahNoProgressThreshold, 5, EXPERIMENTAL, \
463 "After this number of consecutive Full GCs fail to make " \
464 "progress, Shenandoah will raise out of memory errors. Note " \
465 "that progress is determined by ShenandoahCriticalFreeThreshold") \
466 \
467 product(bool, ShenandoahImplicitGCInvokesConcurrent, false, EXPERIMENTAL, \
468 "Should internally-caused GC requests invoke concurrent cycles, " \
469 "should they do the stop-the-world (Degenerated / Full GC)? " \
470 "Many heuristics automatically enable this. This option is " \
471 "similar to global ExplicitGCInvokesConcurrent.") \
472 \
473 product(bool, ShenandoahHumongousMoves, true, DIAGNOSTIC, \
474 "Allow moving humongous regions. This makes GC more resistant " \
475 "to external fragmentation that may otherwise fail other " \
476 "humongous allocations, at the expense of higher GC copying " \
477 "costs. Currently affects stop-the-world (Full) cycle only.") \
478 \
479 product(bool, ShenandoahOOMDuringEvacALot, false, DIAGNOSTIC, \
480 "Testing: simulate OOM during evacuation.") \
481 \
482 product(bool, ShenandoahAllocFailureALot, false, DIAGNOSTIC, \
483 "Testing: make lots of artificial allocation failures.") \
484 \
485 product(uintx, ShenandoahCoalesceChance, 0, DIAGNOSTIC, \
486 "Testing: Abandon remaining mixed collections with this " \
487 "likelihood. Following each mixed collection, abandon all " \
488 "remaining mixed collection candidate regions with likelihood " \
489 "ShenandoahCoalesceChance. Abandoning a mixed collection will " \
490 "cause the old regions to be made parsable, rather than being " \
491 "evacuated.") \
492 range(0, 100) \
493 \
494 product(intx, ShenandoahMarkScanPrefetch, 32, EXPERIMENTAL, \
495 "How many objects to prefetch ahead when traversing mark bitmaps."\
496 "Set to 0 to disable prefetching.") \
497 range(0, 256) \
498 \
499 product(uintx, ShenandoahMarkLoopStride, 1000, EXPERIMENTAL, \
500 "How many items to process during one marking iteration before " \
501 "checking for cancellation, yielding, etc. Larger values improve "\
502 "marking performance at expense of responsiveness.") \
503 \
504 product(uintx, ShenandoahParallelRegionStride, 0, EXPERIMENTAL, \
505 "How many regions to process at once during parallel region " \
506 "iteration. Affects heaps with lots of regions. " \
507 "Set to 0 to let Shenandoah to decide the best value.") \
508 \
509 product(size_t, ShenandoahSATBBufferSize, 1 * K, EXPERIMENTAL, \
510 "Number of entries in an SATB log buffer.") \
511 range(1, max_uintx) \
512 \
513 product(uintx, ShenandoahMaxSATBBufferFlushes, 5, EXPERIMENTAL, \
514 "How many times to maximum attempt to flush SATB buffers at the " \
515 "end of concurrent marking.") \
516 \
517 product(bool, ShenandoahSATBBarrier, true, DIAGNOSTIC, \
518 "Turn on/off SATB barriers in Shenandoah") \
519 \
520 product(bool, ShenandoahIUBarrier, false, DIAGNOSTIC, \
521 "Turn on/off I-U barriers barriers in Shenandoah") \
522 \
523 product(bool, ShenandoahCardBarrier, false, DIAGNOSTIC, \
524 "Turn on/off card-marking post-write barrier in Shenandoah: " \
525 " true when ShenandoahGCMode is generational, false otherwise") \
526 \
527 product(bool, ShenandoahCASBarrier, true, DIAGNOSTIC, \
528 "Turn on/off CAS barriers in Shenandoah") \
529 \
530 product(bool, ShenandoahCloneBarrier, true, DIAGNOSTIC, \
531 "Turn on/off clone barriers in Shenandoah") \
532 \
533 product(bool, ShenandoahLoadRefBarrier, true, DIAGNOSTIC, \
534 "Turn on/off load-reference barriers in Shenandoah") \
535 \
536 product(bool, ShenandoahStackWatermarkBarrier, true, DIAGNOSTIC, \
537 "Turn on/off stack watermark barriers in Shenandoah") \
538 \
539 develop(bool, ShenandoahVerifyOptoBarriers, trueInDebug, \
540 "Verify no missing barriers in C2.") \
541 \
542 product(uintx, ShenandoahOldCompactionReserve, 8, EXPERIMENTAL, \
543 "During generational GC, prevent promotions from filling " \
544 "this number of heap regions. These regions are reserved " \
545 "for the purpose of supporting compaction of old-gen " \
546 "memory. Otherwise, old-gen memory cannot be compacted.") \
547 range(0, 128) \
548 \
549 product(bool, ShenandoahAllowOldMarkingPreemption, true, DIAGNOSTIC, \
550 "Allow young generation collections to suspend concurrent" \
551 " marking in the old generation.") \
552 \
553 product(uintx, ShenandoahAgingCyclePeriod, 1, EXPERIMENTAL, \
554 "With generational mode, increment the age of objects and" \
555 "regions each time this many young-gen GC cycles are completed.") \
556 \
557 notproduct(bool, ShenandoahEnableCardStats, false, \
558 "Enable statistics collection related to clean & dirty cards") \
559 \
560 notproduct(int, ShenandoahCardStatsLogInterval, 50, \
561 "Log cumulative card stats every so many remembered set or " \
562 "update refs scans") \
563 \
564 product(uintx, ShenandoahMinimumOldTimeMs, 100, EXPERIMENTAL, \
565 "Minimum amount of time in milliseconds to run old collections " \
566 "before a young collection is allowed to run. This is intended " \
567 "to prevent starvation of the old collector. Setting this to " \
568 "0 will allow back to back young collections to run during old " \
569 "collections.") \
570 // end of GC_SHENANDOAH_FLAGS
571
572 #endif // SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
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