1 /*
2 * Copyright (c) 2016, 2018, Red Hat, Inc. All rights reserved.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #ifndef SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
25 #define SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP
26
27 #define GC_SHENANDOAH_FLAGS(develop, \
28 develop_pd, \
29 product, \
30 product_pd, \
31 diagnostic, \
32 diagnostic_pd, \
33 experimental, \
34 notproduct, \
35 manageable, \
36 product_rw, \
37 lp64_product, \
38 range, \
39 constraint, \
40 writeable) \
41 \
42 experimental(size_t, ShenandoahHeapRegionSize, 0, \
43 "Size of the Shenandoah regions. Set to zero to detect " \
44 "automatically.") \
45 \
46 experimental(size_t, ShenandoahTargetNumRegions, 2048, \
47 "Target number of regions. We try to get around that many " \
48 "regions, based on Shenandoah{Min,Max}RegionSize.") \
49 \
50 experimental(size_t, ShenandoahMinRegionSize, 256 * K, \
51 "Minimum Shenandoah heap region size.") \
52 \
53 experimental(size_t, ShenandoahMaxRegionSize, 32 * M, \
54 "Maximum Shenandoah heap region size.") \
55 \
56 experimental(intx, ShenandoahHumongousThreshold, 100, \
57 "How large should the object be to get allocated in humongous " \
58 "region, in percents of heap region size. This also caps the " \
59 "maximum TLAB size.") \
60 range(1, 100) \
61 \
62 product(ccstr, ShenandoahGCHeuristics, "adaptive", \
63 "The heuristics to use in Shenandoah GC. Possible values:" \
64 " *) adaptive - adapt to maintain the given amount of free heap;" \
65 " *) static - start concurrent GC when static free heap " \
66 " threshold and static allocation threshold are " \
67 " tripped;" \
68 " *) aggressive - run concurrent GC continuously, evacuate " \
69 " everything;" \
70 " *) compact - run GC with lower footprint target, may end up " \
71 " doing continuous GC, evacuate lots of live " \
72 " objects, uncommit heap aggressively;") \
73 \
74 product(ccstr, ShenandoahGCMode, "normal", \
75 "The GC mode to use in Shenandoah GC. Possible values" \
76 " *) normal - normal GC (mark-evac-update)" \
77 " *) traversal - traversal GC (single-pass)" \
78 " *) passive - disable concurrent GC, do stop-the-world GC") \
79 \
80 experimental(ccstr, ShenandoahUpdateRefsEarly, "adaptive", \
81 "Run a separate concurrent reference updating phase after" \
82 "concurrent evacuation. Possible values: 'on', 'off', 'adaptive'")\
83 \
84 experimental(uintx, ShenandoahRefProcFrequency, 5, \
85 "How often should (weak, soft, etc) references be processed. " \
86 "References get processed at every Nth GC cycle. Set to zero " \
87 "to disable reference processing.") \
88 \
89 experimental(uintx, ShenandoahUnloadClassesFrequency, 5, \
90 "How often should classes get unloaded. " \
91 "Class unloading is performed at every Nth GC cycle. " \
92 "Set to zero to disable class unloading during concurrent GC.") \
93 \
94 experimental(uintx, ShenandoahGarbageThreshold, 60, \
95 "Sets the percentage of garbage a region need to contain before " \
96 "it can be marked for collection. Does not apply to all " \
97 "heuristics.") \
98 range(0,100) \
99 \
100 experimental(uintx, ShenandoahFreeThreshold, 10, \
101 "Set the percentage of free heap at which a GC cycle is started. "\
102 "Does not apply to all heuristics.") \
103 range(0,100) \
104 \
105 experimental(uintx, ShenandoahInitFreeThreshold, 70, \
106 "Initial remaining free heap threshold for learning steps in " \
107 "heuristics. In percents of total heap size. Does not apply to " \
108 "all heuristics.") \
109 range(0,100) \
110 \
111 experimental(uintx, ShenandoahMinFreeThreshold, 10, \
112 "Minimum remaining free space threshold, after which collection " \
113 "definitely triggers. Does not apply to all heuristics.") \
114 range(0,100) \
115 \
116 experimental(uintx, ShenandoahAllocationThreshold, 0, \
117 "Set percentage of memory allocated since last GC cycle before " \
118 "a new GC cycle can be started. Set to zero to effectively " \
119 "disable.") \
120 range(0,100) \
121 \
122 experimental(uintx, ShenandoahLearningSteps, 5, \
123 "Number of GC cycles to run in order to learn application " \
124 "and GC performance for adaptive heuristics.") \
125 range(0,100) \
126 \
127 experimental(uintx, ShenandoahImmediateThreshold, 90, \
128 "If mark identifies more than this much immediate garbage " \
129 "regions, it shall recycle them, and shall not continue the " \
130 "rest of the GC cycle. The value is in percents of total " \
131 "number of candidate regions for collection set. Setting this " \
132 "threshold to 100% effectively disables this shortcut.") \
133 range(0,100) \
134 \
135 experimental(uintx, ShenandoahMergeUpdateRefsMinGap, 100, \
136 "If GC is currently running in separate update-refs mode " \
137 "this numbers gives the threshold when to switch to " \
138 "merged update-refs mode. Number is percentage relative to" \
139 "duration(marking)+duration(update-refs).") \
140 \
141 experimental(uintx, ShenandoahMergeUpdateRefsMaxGap, 200, \
142 "If GC is currently running in merged update-refs mode " \
143 "this numbers gives the threshold when to switch to " \
144 "separate update-refs mode. Number is percentage relative " \
145 "to duration(marking)+duration(update-refs).") \
146 \
147 experimental(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, \
148 "Adaptive and dynamic heuristics would guarantee a GC cycle " \
149 "at least with this interval. This is useful when large idle" \
150 " intervals are present, where GC can run without stealing " \
151 "time from active application. Time is in milliseconds.") \
152 \
153 experimental(bool, ShenandoahAlwaysClearSoftRefs, false, \
154 "Clear soft references always, instead of using any smart " \
155 "cleanup policy. This minimizes footprint at expense of more " \
156 "softref churn in applications.") \
157 \
158 experimental(bool, ShenandoahUncommit, true, \
159 "Allow Shenandoah to uncommit unused memory.") \
160 \
161 experimental(uintx, ShenandoahUncommitDelay, 5*60*1000, \
162 "Shenandoah would start to uncommit memory for regions that were" \
163 " not used for more than this time. First use after that would " \
164 "incur allocation stalls. Actively used regions would never be " \
165 "uncommitted, because they never decay. Time is in milliseconds." \
166 "Setting this delay to 0 effectively makes Shenandoah to " \
167 "uncommit the regions almost immediately.") \
168 \
169 experimental(bool, ShenandoahRegionSampling, false, \
170 "Turns on heap region sampling via JVMStat") \
171 \
172 experimental(int, ShenandoahRegionSamplingRate, 40, \
173 "Sampling rate for heap region sampling. " \
174 "Number of milliseconds between samples") \
175 \
176 experimental(uintx, ShenandoahControlIntervalMin, 1, \
177 "The minumum sleep interval for control loop that drives " \
178 "the cycles. Lower values would increase GC responsiveness " \
179 "to changing heap conditions, at the expense of higher perf " \
180 "overhead. Time is in milliseconds.") \
181 \
182 experimental(uintx, ShenandoahControlIntervalMax, 10, \
183 "The maximum sleep interval for control loop that drives " \
184 "the cycles. Lower values would increase GC responsiveness " \
185 "to changing heap conditions, at the expense of higher perf " \
186 "overhead. Time is in milliseconds.") \
187 \
188 experimental(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, \
189 "The time period for one step in control loop interval " \
190 "adjustment. Lower values make adjustments faster, at the " \
191 "expense of higher perf overhead. Time is in milliseconds.") \
192 \
193 experimental(bool, ShenandoahCriticalControlThreadPriority, false, \
194 "Shenandoah control thread runs at critical scheduling priority.")\
195 \
196 diagnostic(bool, ShenandoahVerify, false, \
197 "Verify the Shenandoah garbage collector") \
198 \
199 diagnostic(intx, ShenandoahVerifyLevel, 4, \
200 "Shenandoah verification level: " \
201 "0 = basic heap checks; " \
202 "1 = previous level, plus basic region checks; " \
203 "2 = previous level, plus all roots; " \
204 "3 = previous level, plus all reachable objects; " \
205 "4 = previous level, plus all marked objects") \
206 \
207 diagnostic(bool, ShenandoahElasticTLAB, true, \
208 "Use Elastic TLABs with Shenandoah") \
209 \
210 diagnostic(bool, ShenandoahAllowMixedAllocs, true, \
211 "Allow mixing mutator and collector allocations in a single " \
212 "region") \
213 \
214 experimental(uintx, ShenandoahAllocSpikeFactor, 5, \
215 "The amount of heap space to reserve for absorbing the " \
216 "allocation spikes. Larger value wastes more memory in " \
217 "non-emergency cases, but provides more safety in emergency " \
218 "cases. In percents of total heap size.") \
219 range(0,100) \
220 \
221 experimental(uintx, ShenandoahEvacReserve, 5, \
222 "Maximum amount of free space to reserve for evacuation. " \
223 "Larger values make GC more aggressive, while leaving less " \
224 "headroom for application to allocate in. " \
225 "In percents of total heap size.") \
226 range(1,100) \
227 \
228 experimental(double, ShenandoahEvacWaste, 1.2, \
229 "How much waste evacuations produce within the reserved " \
230 "space. Larger values make evacuations more resilient " \
231 "against allocation failures, at expense of smaller csets " \
232 "on each cycle.") \
233 range(1.0,100.0) \
234 \
235 experimental(bool, ShenandoahEvacReserveOverflow, true, \
236 "Allow evacuations to overflow the reserved space. " \
237 "Enabling it will make evacuations more resilient when " \
238 "evacuation reserve/waste is incorrect, at the risk that " \
239 "application allocations run out of memory too early.") \
240 \
241 diagnostic(bool, ShenandoahAllocationTrace, false, \
242 "Trace allocation latencies and stalls. Can be expensive when " \
243 "lots of allocations happen, and may introduce scalability " \
244 "bottlenecks.") \
245 \
246 diagnostic(intx, ShenandoahAllocationStallThreshold, 10000, \
247 "When allocation tracing is enabled, the allocation stalls " \
248 "larger than this threshold would be reported as warnings. " \
249 "Time is in microseconds.") \
250 \
251 experimental(uintx, ShenandoahEvacAssist, 10, \
252 "How many objects to evacuate on LRB assist path. " \
253 "Use zero to disable.") \
254 \
255 experimental(bool, ShenandoahPacing, true, \
256 "Pace application allocations to give GC chance to start " \
257 "and complete before allocation failure is reached.") \
258 \
259 experimental(uintx, ShenandoahPacingMaxDelay, 10, \
260 "Max delay for pacing application allocations. " \
261 "Time is in milliseconds.") \
262 \
263 experimental(uintx, ShenandoahPacingIdleSlack, 2, \
264 "Percent of heap counted as non-taxable allocations during idle. "\
265 "Larger value makes the pacing milder during idle phases, " \
266 "requiring less rendezvous with control thread. Lower value " \
267 "makes the pacing control less responsive to out-of-cycle allocs.")\
268 range(0, 100) \
269 \
270 experimental(uintx, ShenandoahPacingCycleSlack, 10, \
271 "Percent of free space taken as non-taxable allocations during " \
272 "the GC cycle. Larger value makes the pacing milder at the " \
273 "beginning of the GC cycle. Lower value makes the pacing less " \
274 "uniform during the cycle.") \
275 range(0, 100) \
276 \
277 experimental(double, ShenandoahPacingSurcharge, 1.1, \
278 "Additional pacing tax surcharge to help unclutter the heap. " \
279 "Larger values makes the pacing more aggressive. Lower values " \
280 "risk GC cycles finish with less memory than were available at " \
281 "the beginning of it.") \
282 range(1.0, 100.0) \
283 \
284 experimental(uintx, ShenandoahCriticalFreeThreshold, 1, \
285 "Percent of heap that needs to be free after recovery cycles, " \
286 "either Degenerated or Full GC. If this much space is not " \
287 "available, next recovery step would triggered.") \
288 range(0, 100) \
289 \
290 diagnostic(bool, ShenandoahDegeneratedGC, true, \
291 "Use Degenerated GC as the graceful degradation step. Disabling " \
292 "this leads to degradation to Full GC") \
293 \
294 experimental(uintx, ShenandoahFullGCThreshold, 3, \
295 "How many back-to-back Degenerated GCs to do before triggering " \
296 "a Full GC.") \
297 \
298 experimental(bool, ShenandoahImplicitGCInvokesConcurrent, false, \
299 "Should internally-caused GCs invoke concurrent cycles, or go to" \
300 "stop-the-world (degenerated/full)?") \
301 \
302 diagnostic(bool, ShenandoahHumongousMoves, true, \
303 "Allow moving humongous regions. This makes GC more resistant " \
304 "to external fragmentation that may otherwise fail other " \
305 "humongous allocations, at the expense of higher GC copying " \
306 "costs. Currently affects stop-the-world (full) cycle only.") \
307 \
308 diagnostic(bool, ShenandoahOOMDuringEvacALot, false, \
309 "Simulate OOM during evacuation frequently.") \
310 \
311 diagnostic(bool, ShenandoahAllocFailureALot, false, \
312 "Make lots of artificial allocation failures.") \
313 \
314 diagnostic(bool, ShenandoahTerminationTrace, false, \
315 "Tracing task termination timings") \
316 \
317 diagnostic(bool, ShenandoahAlwaysPreTouch, false, \
318 "Pre-touch heap memory, overrides global AlwaysPreTouch") \
319 \
320 experimental(intx, ShenandoahMarkScanPrefetch, 32, \
321 "How many objects to prefetch ahead when traversing mark bitmaps."\
322 "Set to 0 to disable prefetching.") \
323 range(0, 256) \
324 \
325 experimental(uintx, ShenandoahMarkLoopStride, 1000, \
326 "How many items are processed during one marking step") \
327 \
328 experimental(uintx, ShenandoahParallelRegionStride, 1024, \
329 "How many regions are processed in one stride during parallel " \
330 "iteration.") \
331 \
332 experimental(size_t, ShenandoahSATBBufferSize, 1 * K, \
333 "Number of entries in an SATB log buffer.") \
334 range(1, max_uintx) \
335 \
336 experimental(uintx, ShenandoahSATBBufferFlushInterval, 100, \
337 "Forcefully flush non-empty SATB buffers at this interval. " \
338 "Time is in milliseconds.") \
339 \
340 experimental(uint, ShenandoahParallelSafepointThreads, 4, \
341 "Number of parallel threads used for safepoint prolog/epilog") \
342 \
343 experimental(bool, ShenandoahPreclean, true, \
344 "Do concurrent preclean phase before final mark: process " \
345 "definitely alive references to avoid dealing with them during " \
346 "pause.") \
347 \
348 experimental(bool, ShenandoahSuspendibleWorkers, false, \
349 "Suspend concurrent GC worker threads at safepoints") \
350 \
351 diagnostic(bool, ShenandoahSATBBarrier, true, \
352 "Turn on/off SATB barriers in Shenandoah") \
353 \
354 diagnostic(bool, ShenandoahKeepAliveBarrier, true, \
355 "Turn on/off keep alive barriers in Shenandoah") \
356 \
357 diagnostic(bool, ShenandoahStoreValEnqueueBarrier, false, \
358 "Turn on/off enqueuing of oops for storeval barriers") \
359 \
360 diagnostic(bool, ShenandoahCASBarrier, true, \
361 "Turn on/off CAS barriers in Shenandoah") \
362 \
363 diagnostic(bool, ShenandoahCloneBarrier, true, \
364 "Turn on/off clone barriers in Shenandoah") \
365 \
366 diagnostic(bool, ShenandoahLoadRefBarrier, true, \
367 "Turn on/off load-reference barriers in Shenandoah") \
368 \
369 experimental(bool, ShenandoahConcurrentScanCodeRoots, true, \
370 "Scan code roots concurrently, instead of during a pause") \
371 \
372 experimental(uintx, ShenandoahCodeRootsStyle, 2, \
373 "Use this style to scan code cache:" \
374 " 0 - sequential iterator;" \
375 " 1 - parallel iterator;" \
376 " 2 - parallel iterator with cset filters;") \
377 \
378 diagnostic(bool, ShenandoahOptimizeStaticFinals, true, \
379 "Optimize barriers on static final fields. " \
380 "Turn it off for maximum compatibility with reflection or JNI " \
381 "code that manipulates final fields.") \
382 \
383 experimental(bool, ShenandoahCommonGCStateLoads, false, \
384 "Enable commonming for GC state loads in generated code.") \
385 \
386 develop(bool, ShenandoahVerifyOptoBarriers, false, \
387 "Verify no missing barriers in C2") \
388 \
389 experimental(bool, ShenandoahLoopOptsAfterExpansion, true, \
390 "Attempt more loop opts after barrier expansion") \
391 \
392 diagnostic(bool, ShenandoahSelfFixing, true, \
393 "Fix references with load reference barrier. Disabling this " \
394 "might degrade performance.") \
395
396
397 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP