1 /*
2 * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2016, 2020, 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 *
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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 diagnostic, \
34 diagnostic_pd, \
35 experimental, \
36 notproduct, \
37 manageable, \
38 product_rw, \
39 lp64_product, \
40 range, \
41 constraint) \
42 \
43 experimental(size_t, ShenandoahHeapRegionSize, 0, \
44 "Size of the Shenandoah regions. Set to zero to detect " \
45 "automatically.") \
46 \
47 experimental(size_t, ShenandoahTargetNumRegions, 2048, \
48 "Target number of regions. We try to get around that many " \
49 "regions, based on Shenandoah{Min,Max}RegionSize.") \
50 \
51 experimental(size_t, ShenandoahMinRegionSize, 256 * K, \
52 "Minimum Shenandoah heap region size.") \
53 \
54 experimental(size_t, ShenandoahMaxRegionSize, 32 * M, \
55 "Maximum Shenandoah heap region size.") \
56 \
57 experimental(intx, ShenandoahHumongousThreshold, 100, \
58 "How large should the object be to get allocated in humongous " \
59 "region, in percents of heap region size. This also caps the " \
60 "maximum TLAB size.") \
61 range(1, 100) \
62 \
63 experimental(ccstr, ShenandoahGCHeuristics, "adaptive", \
64 "The heuristics to use in Shenandoah GC. Possible values:" \
65 " *) adaptive - adapt to maintain the given amount of free heap;" \
66 " *) static - start concurrent GC when static free heap " \
67 " threshold and static allocation threshold are " \
68 " tripped;" \
69 " *) aggressive - run concurrent GC continuously, evacuate " \
70 " everything;" \
71 " *) compact - run GC with lower footprint target, may end up " \
72 " doing continuous GC, evacuate lots of live " \
73 " objects, uncommit heap aggressively;") \
74 \
75 experimental(ccstr, ShenandoahGCMode, "normal", \
76 "The GC mode to use in Shenandoah GC. Possible values" \
77 " *) normal - normal GC (mark-evac-update)" \
78 " *) traversal - traversal GC (single-pass)" \
79 " *) passive - disable concurrent GC, do stop-the-world GC") \
80 \
81 experimental(ccstr, ShenandoahUpdateRefsEarly, "adaptive", \
82 "Run a separate concurrent reference updating phase after" \
83 "concurrent evacuation. Possible values: 'on', 'off', 'adaptive'")\
84 \
85 experimental(uintx, ShenandoahRefProcFrequency, 5, \
86 "How often should (weak, soft, etc) references be processed. " \
87 "References get processed at every Nth GC cycle. Set to zero " \
88 "to disable reference processing.") \
89 \
90 experimental(uintx, ShenandoahUnloadClassesFrequency, 1, \
91 "How often should classes get unloaded. " \
92 "Class unloading is performed at every Nth GC cycle. " \
93 "Set to zero to disable class unloading during concurrent GC.") \
94 \
95 experimental(uintx, ShenandoahGarbageThreshold, 60, \
96 "Sets the percentage of garbage a region need to contain before " \
97 "it can be marked for collection. Does not apply to all " \
98 "heuristics.") \
99 range(0,100) \
100 \
101 experimental(uintx, ShenandoahInitFreeThreshold, 70, \
102 "Initial remaining free heap threshold for learning steps in " \
103 "heuristics. In percents of total heap size. Does not apply to " \
104 "all heuristics.") \
105 range(0,100) \
106 \
107 experimental(uintx, ShenandoahMinFreeThreshold, 10, \
108 "Minimum remaining free space threshold, after which collection " \
109 "definitely triggers. Does not apply to all heuristics.") \
110 range(0,100) \
111 \
112 experimental(uintx, ShenandoahAllocationThreshold, 0, \
113 "Set percentage of memory allocated since last GC cycle before " \
114 "a new GC cycle can be started. Set to zero to effectively " \
115 "disable.") \
116 range(0,100) \
117 \
118 experimental(uintx, ShenandoahLearningSteps, 5, \
119 "Number of GC cycles to run in order to learn application " \
120 "and GC performance for adaptive heuristics.") \
121 range(0,100) \
122 \
123 experimental(uintx, ShenandoahImmediateThreshold, 90, \
124 "If mark identifies more than this much immediate garbage " \
125 "regions, it shall recycle them, and shall not continue the " \
126 "rest of the GC cycle. The value is in percents of total " \
127 "number of candidate regions for collection set. Setting this " \
128 "threshold to 100% effectively disables this shortcut.") \
129 range(0,100) \
130 \
131 experimental(uintx, ShenandoahMergeUpdateRefsMinGap, 100, \
132 "If GC is currently running in separate update-refs mode " \
133 "this numbers gives the threshold when to switch to " \
134 "merged update-refs mode. Number is percentage relative to" \
135 "duration(marking)+duration(update-refs).") \
136 \
137 experimental(uintx, ShenandoahMergeUpdateRefsMaxGap, 200, \
138 "If GC is currently running in merged update-refs mode " \
139 "this numbers gives the threshold when to switch to " \
140 "separate update-refs mode. Number is percentage relative " \
141 "to duration(marking)+duration(update-refs).") \
142 \
143 experimental(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, \
144 "Most heuristics would guarantee a concurrent GC cycle at " \
145 "least with this interval. This is useful when large idle " \
146 "intervals are present, where GC can run without stealing " \
147 "time from active application. Time is in milliseconds. " \
148 "(Setting this interval to 0 disables this feature).") \
149 \
150 experimental(bool, ShenandoahAlwaysClearSoftRefs, false, \
151 "Clear soft references always, instead of using any smart " \
152 "cleanup policy. This minimizes footprint at expense of more " \
153 "softref churn in applications.") \
154 \
155 experimental(bool, ShenandoahUncommit, true, \
156 "Allow Shenandoah to uncommit unused memory.") \
157 \
158 experimental(uintx, ShenandoahUncommitDelay, 5*60*1000, \
159 "Shenandoah would start to uncommit memory for regions that were" \
160 " not used for more than this time. First use after that would " \
161 "incur allocation stalls. Actively used regions would never be " \
162 "uncommitted, because they never decay. Time is in milliseconds." \
163 "Setting this delay to 0 effectively makes Shenandoah to " \
164 "uncommit the regions almost immediately.") \
165 \
166 experimental(bool, ShenandoahRegionSampling, false, \
167 "Turns on heap region sampling via JVMStat") \
168 \
169 experimental(int, ShenandoahRegionSamplingRate, 40, \
170 "Sampling rate for heap region sampling. " \
171 "Number of milliseconds between samples") \
172 \
173 experimental(uintx, ShenandoahControlIntervalMin, 1, \
174 "The minumum sleep interval for control loop that drives " \
175 "the cycles. Lower values would increase GC responsiveness " \
176 "to changing heap conditions, at the expense of higher perf " \
177 "overhead. Time is in milliseconds.") \
178 \
179 experimental(uintx, ShenandoahControlIntervalMax, 10, \
180 "The maximum sleep interval for control loop that drives " \
181 "the cycles. Lower values would increase GC responsiveness " \
182 "to changing heap conditions, at the expense of higher perf " \
183 "overhead. Time is in milliseconds.") \
184 \
185 experimental(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, \
186 "The time period for one step in control loop interval " \
187 "adjustment. Lower values make adjustments faster, at the " \
188 "expense of higher perf overhead. Time is in milliseconds.") \
189 \
190 experimental(bool, ShenandoahCriticalControlThreadPriority, false, \
191 "Shenandoah control thread runs at critical scheduling priority.")\
192 \
193 diagnostic(bool, ShenandoahVerify, false, \
194 "Verify the Shenandoah garbage collector") \
195 \
196 diagnostic(intx, ShenandoahVerifyLevel, 4, \
197 "Shenandoah verification level: " \
198 "0 = basic heap checks; " \
199 "1 = previous level, plus basic region checks; " \
200 "2 = previous level, plus all roots; " \
201 "3 = previous level, plus all reachable objects; " \
202 "4 = previous level, plus all marked objects") \
203 \
204 diagnostic(bool, ShenandoahElasticTLAB, true, \
205 "Use Elastic TLABs with Shenandoah") \
206 \
207 diagnostic(bool, ShenandoahAllowMixedAllocs, true, \
208 "Allow mixing mutator and collector allocations in a single " \
209 "region") \
210 \
211 experimental(uintx, ShenandoahAllocSpikeFactor, 5, \
212 "The amount of heap space to reserve for absorbing the " \
213 "allocation spikes. Larger value wastes more memory in " \
214 "non-emergency cases, but provides more safety in emergency " \
215 "cases. In percents of total heap size.") \
216 range(0,100) \
217 \
218 experimental(uintx, ShenandoahEvacReserve, 5, \
219 "Maximum amount of free space to reserve for evacuation. " \
220 "Larger values make GC more aggressive, while leaving less " \
221 "headroom for application to allocate in. " \
222 "In percents of total heap size.") \
223 range(1,100) \
224 \
225 experimental(double, ShenandoahEvacWaste, 1.2, \
226 "How much waste evacuations produce within the reserved " \
227 "space. Larger values make evacuations more resilient " \
228 "against allocation failures, at expense of smaller csets " \
229 "on each cycle.") \
230 range(1.0,100.0) \
231 \
232 experimental(bool, ShenandoahEvacReserveOverflow, true, \
233 "Allow evacuations to overflow the reserved space. " \
234 "Enabling it will make evacuations more resilient when " \
235 "evacuation reserve/waste is incorrect, at the risk that " \
236 "application allocations run out of memory too early.") \
237 \
238 experimental(uintx, ShenandoahEvacAssist, 10, \
239 "How many objects to evacuate on LRB assist path. " \
240 "Use zero to disable.") \
241 \
242 experimental(bool, ShenandoahPacing, true, \
243 "Pace application allocations to give GC chance to start " \
244 "and complete before allocation failure is reached.") \
245 \
246 experimental(uintx, ShenandoahPacingMaxDelay, 10, \
247 "Max delay for pacing application allocations. " \
248 "Time is in milliseconds.") \
249 \
250 experimental(uintx, ShenandoahPacingIdleSlack, 2, \
251 "Percent of heap counted as non-taxable allocations during idle. "\
252 "Larger value makes the pacing milder during idle phases, " \
253 "requiring less rendezvous with control thread. Lower value " \
254 "makes the pacing control less responsive to out-of-cycle allocs.")\
255 range(0, 100) \
256 \
257 experimental(uintx, ShenandoahPacingCycleSlack, 10, \
258 "Percent of free space taken as non-taxable allocations during " \
259 "the GC cycle. Larger value makes the pacing milder at the " \
260 "beginning of the GC cycle. Lower value makes the pacing less " \
261 "uniform during the cycle.") \
262 range(0, 100) \
263 \
264 experimental(double, ShenandoahPacingSurcharge, 1.1, \
265 "Additional pacing tax surcharge to help unclutter the heap. " \
266 "Larger values makes the pacing more aggressive. Lower values " \
267 "risk GC cycles finish with less memory than were available at " \
268 "the beginning of it.") \
269 range(1.0, 100.0) \
270 \
271 experimental(uintx, ShenandoahCriticalFreeThreshold, 1, \
272 "Percent of heap that needs to be free after recovery cycles, " \
273 "either Degenerated or Full GC. If this much space is not " \
274 "available, next recovery step would triggered.") \
275 range(0, 100) \
276 \
277 diagnostic(bool, ShenandoahDegeneratedGC, true, \
278 "Use Degenerated GC as the graceful degradation step. Disabling " \
279 "this leads to degradation to Full GC") \
280 \
281 experimental(uintx, ShenandoahFullGCThreshold, 3, \
282 "How many back-to-back Degenerated GCs to do before triggering " \
283 "a Full GC.") \
284 \
285 experimental(bool, ShenandoahImplicitGCInvokesConcurrent, false, \
286 "Should internally-caused GCs invoke concurrent cycles, or go to" \
287 "stop-the-world (degenerated/full)?") \
288 \
289 diagnostic(bool, ShenandoahHumongousMoves, true, \
290 "Allow moving humongous regions. This makes GC more resistant " \
291 "to external fragmentation that may otherwise fail other " \
292 "humongous allocations, at the expense of higher GC copying " \
293 "costs. Currently affects stop-the-world (full) cycle only.") \
294 \
295 diagnostic(bool, ShenandoahOOMDuringEvacALot, false, \
296 "Simulate OOM during evacuation frequently.") \
297 \
298 diagnostic(bool, ShenandoahAllocFailureALot, false, \
299 "Make lots of artificial allocation failures.") \
300 \
301 diagnostic(bool, ShenandoahAlwaysPreTouch, false, \
302 "Pre-touch heap memory, overrides global AlwaysPreTouch") \
303 \
304 experimental(intx, ShenandoahMarkScanPrefetch, 32, \
305 "How many objects to prefetch ahead when traversing mark bitmaps."\
306 "Set to 0 to disable prefetching.") \
307 range(0, 256) \
308 \
309 experimental(uintx, ShenandoahMarkLoopStride, 1000, \
310 "How many items are processed during one marking step") \
311 \
312 experimental(uintx, ShenandoahParallelRegionStride, 1024, \
313 "How many regions are processed in one stride during parallel " \
314 "iteration.") \
315 \
316 experimental(size_t, ShenandoahSATBBufferSize, 1 * K, \
317 "Number of entries in an SATB log buffer.") \
318 range(1, max_uintx) \
319 \
320 experimental(uintx, ShenandoahSATBBufferFlushInterval, 100, \
321 "Forcefully flush non-empty SATB buffers at this interval. " \
322 "Time is in milliseconds.") \
323 \
324 experimental(uint, ShenandoahParallelSafepointThreads, 4, \
325 "Number of parallel threads used for safepoint prolog/epilog") \
326 \
327 diagnostic(bool, ShenandoahPreclean, true, \
328 "Do concurrent preclean phase before final mark: process " \
329 "definitely alive references to avoid dealing with them during " \
330 "pause.") \
331 \
332 experimental(bool, ShenandoahSuspendibleWorkers, false, \
333 "Suspend concurrent GC worker threads at safepoints") \
334 \
335 diagnostic(bool, ShenandoahSATBBarrier, true, \
336 "Turn on/off SATB barriers in Shenandoah") \
337 \
338 diagnostic(bool, ShenandoahKeepAliveBarrier, true, \
339 "Turn on/off keep alive barriers in Shenandoah") \
340 \
341 diagnostic(bool, ShenandoahStoreValEnqueueBarrier, false, \
342 "Turn on/off enqueuing of oops for storeval barriers") \
343 \
344 diagnostic(bool, ShenandoahCASBarrier, true, \
345 "Turn on/off CAS barriers in Shenandoah") \
346 \
347 diagnostic(bool, ShenandoahCloneBarrier, true, \
348 "Turn on/off clone barriers in Shenandoah") \
349 \
350 diagnostic(bool, ShenandoahLoadRefBarrier, true, \
351 "Turn on/off load-reference barriers in Shenandoah") \
352 \
353 diagnostic(bool, ShenandoahConcurrentScanCodeRoots, true, \
354 "Scan code roots concurrently, instead of during a pause") \
355 \
356 diagnostic(uintx, ShenandoahCodeRootsStyle, 2, \
357 "Use this style to scan code cache:" \
358 " 0 - sequential iterator;" \
359 " 1 - parallel iterator;" \
360 " 2 - parallel iterator with cset filters;") \
361 \
362 diagnostic(bool, ShenandoahOptimizeStaticFinals, true, \
363 "Optimize barriers on static final fields. " \
364 "Turn it off for maximum compatibility with reflection or JNI " \
365 "code that manipulates final fields.") \
366 \
367 develop(bool, ShenandoahVerifyOptoBarriers, false, \
368 "Verify no missing barriers in C2") \
369 \
370 diagnostic(bool, ShenandoahLoopOptsAfterExpansion, true, \
371 "Attempt more loop opts after barrier expansion") \
372 \
373 diagnostic(bool, ShenandoahSelfFixing, true, \
374 "Fix references with load reference barrier. Disabling this " \
375 "might degrade performance.") \
376
377
378 #endif // SHARE_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP