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 #include "runtime/globals.hpp"
28
29 #define SHENANDOAH_FLAGS(develop, \
30 develop_pd, \
31 product, \
32 product_pd, \
33 diagnostic, \
34 experimental, \
35 notproduct, \
36 manageable, \
37 product_rw) \
38 \
39 experimental(uintx, ShenandoahHeapRegionSize, 0, \
40 "Size of the Shenandoah regions. Set to zero to detect " \
41 "automatically.") \
42 \
43 experimental(uintx, ShenandoahTargetNumRegions, 2048, \
44 "Target number of regions. We try to get around that many " \
45 "regions, based on Shenandoah{Min,Max}RegionSize.") \
46 \
47 experimental(uintx, ShenandoahMinRegionSize, 256 * K, \
48 "Minimum Shenandoah heap region size.") \
49 \
50 experimental(uintx, ShenandoahMaxRegionSize, 32 * M, \
51 "Maximum Shenandoah heap region size.") \
52 \
53 experimental(intx, ShenandoahHumongousThreshold, 100, \
54 "How large should the object be to get allocated in humongous " \
55 "region, in percents of heap region size. This also caps the " \
56 "maximum TLAB size.") \
57 \
58 product(ccstr, ShenandoahGCHeuristics, "adaptive", \
59 "The heuristics to use in Shenandoah GC. Possible values:" \
60 " *) adaptive - adapt to maintain the given amount of free heap;" \
61 " *) static - start concurrent GC when static free heap " \
62 " threshold and static allocation threshold are " \
63 " tripped;" \
64 " *) aggressive - run concurrent GC continuously, evacuate " \
65 " everything;" \
66 " *) compact - run GC with lower footprint target, may end up " \
67 " doing continuous GC, evacuate lots of live " \
68 " objects, uncommit heap aggressively;") \
69 \
70 product(ccstr, ShenandoahGCMode, "normal", \
71 "The GC mode to use in Shenandoah GC. Possible values" \
72 " *) normal - normal GC (mark-evac-update)" \
73 " *) traversal - traversal GC (single-pass)" \
74 " *) passive - disable concurrent GC, do stop-the-world GC") \
75 \
76 experimental(ccstr, ShenandoahUpdateRefsEarly, "adaptive", \
77 "Run a separate concurrent reference updating phase after" \
78 "concurrent evacuation. Possible values: 'on', 'off', 'adaptive'")\
79 \
80 experimental(uintx, ShenandoahRefProcFrequency, 5, \
81 "How often should (weak, soft, etc) references be processed. " \
82 "References get processed at every Nth GC cycle. Set to zero " \
83 "to disable reference processing.") \
84 \
85 experimental(uintx, ShenandoahUnloadClassesFrequency, 5, \
86 "How often should classes get unloaded. " \
87 "Class unloading is performed at every Nth GC cycle. " \
88 "Set to zero to disable class unloading during concurrent GC.") \
89 \
90 experimental(uintx, ShenandoahGarbageThreshold, 60, \
91 "Sets the percentage of garbage a region need to contain before " \
92 "it can be marked for collection. Does not apply to all " \
93 "heuristics.") \
94 \
95 experimental(uintx, ShenandoahFreeThreshold, 10, \
96 "Set the percentage of free heap at which a GC cycle is started. "\
97 "Does not apply to all heuristics.") \
98 \
99 experimental(uintx, ShenandoahInitFreeThreshold, 70, \
100 "Initial remaining free heap threshold for learning steps in " \
101 "heuristics. In percents of total heap size. Does not apply to " \
102 "all heuristics.") \
103 \
104 experimental(uintx, ShenandoahMinFreeThreshold, 10, \
105 "Minimum remaining free space threshold, after which collection " \
106 "definitely triggers. Does not apply to all heuristics.") \
107 \
108 experimental(uintx, ShenandoahAllocationThreshold, 0, \
109 "Set percentage of memory allocated since last GC cycle before " \
110 "a new GC cycle can be started. Set to zero to effectively " \
111 "disable.") \
112 \
113 experimental(uintx, ShenandoahLearningSteps, 5, \
114 "Number of GC cycles to run in order to learn application " \
115 "and GC performance for adaptive heuristics.") \
116 \
117 experimental(uintx, ShenandoahImmediateThreshold, 90, \
118 "If mark identifies more than this much immediate garbage " \
119 "regions, it shall recycle them, and shall not continue the " \
120 "rest of the GC cycle. The value is in percents of total " \
121 "number of candidate regions for collection set. Setting this " \
122 "threshold to 100% effectively disables this shortcut.") \
123 \
124 experimental(uintx, ShenandoahMergeUpdateRefsMinGap, 100, \
125 "If GC is currently running in separate update-refs mode " \
126 "this numbers gives the threshold when to switch to " \
127 "merged update-refs mode. Number is percentage relative to" \
128 "duration(marking)+duration(update-refs).") \
129 \
130 experimental(uintx, ShenandoahMergeUpdateRefsMaxGap, 200, \
131 "If GC is currently running in merged update-refs mode " \
132 "this numbers gives the threshold when to switch to " \
133 "separate update-refs mode. Number is percentage relative " \
134 "to duration(marking)+duration(update-refs).") \
135 \
136 experimental(uintx, ShenandoahGuaranteedGCInterval, 5*60*1000, \
137 "Adaptive and dynamic heuristics would guarantee a GC cycle " \
138 "at least with this interval. This is useful when large idle" \
139 " intervals are present, where GC can run without stealing " \
140 "time from active application. Time is in milliseconds.") \
141 \
142 experimental(bool, ShenandoahAlwaysClearSoftRefs, false, \
143 "Clear soft references always, instead of using any smart " \
144 "cleanup policy. This minimizes footprint at expense of more " \
145 "softref churn in applications.") \
146 \
147 experimental(bool, ShenandoahUncommit, true, \
148 "Allow Shenandoah to uncommit unused memory.") \
149 \
150 experimental(uintx, ShenandoahUncommitDelay, 5*60*1000, \
151 "Shenandoah would start to uncommit memory for regions that were" \
152 " not used for more than this time. First use after that would " \
153 "incur allocation stalls. Actively used regions would never be " \
154 "uncommitted, because they never decay. Time is in milliseconds." \
155 "Setting this delay to 0 effectively makes Shenandoah to " \
156 "uncommit the regions almost immediately.") \
157 \
158 experimental(bool, ShenandoahRegionSampling, false, \
159 "Turns on heap region sampling via JVMStat") \
160 \
161 experimental(int, ShenandoahRegionSamplingRate, 40, \
162 "Sampling rate for heap region sampling. " \
163 "Number of milliseconds between samples") \
164 \
165 experimental(uintx, ShenandoahControlIntervalMin, 1, \
166 "The minumum sleep interval for control loop that drives " \
167 "the cycles. Lower values would increase GC responsiveness " \
168 "to changing heap conditions, at the expense of higher perf " \
169 "overhead. Time is in milliseconds.") \
170 \
171 experimental(uintx, ShenandoahControlIntervalMax, 10, \
172 "The maximum sleep interval for control loop that drives " \
173 "the cycles. Lower values would increase GC responsiveness " \
174 "to changing heap conditions, at the expense of higher perf " \
175 "overhead. Time is in milliseconds.") \
176 \
177 experimental(uintx, ShenandoahControlIntervalAdjustPeriod, 1000, \
178 "The time period for one step in control loop interval " \
179 "adjustment. Lower values make adjustments faster, at the " \
180 "expense of higher perf overhead. Time is in milliseconds.") \
181 \
182 experimental(bool, ShenandoahCriticalControlThreadPriority, false, \
183 "Shenandoah control thread runs at critical scheduling priority.")\
184 \
185 diagnostic(bool, ShenandoahVerify, false, \
186 "Verify the Shenandoah garbage collector") \
187 \
188 diagnostic(intx, ShenandoahVerifyLevel, 4, \
189 "Shenandoah verification level: " \
190 "0 = basic heap checks; " \
191 "1 = previous level, plus basic region checks; " \
192 "2 = previous level, plus all roots; " \
193 "3 = previous level, plus all reachable objects; " \
194 "4 = previous level, plus all marked objects") \
195 \
196 diagnostic(bool, ShenandoahElasticTLAB, true, \
197 "Use Elastic TLABs with Shenandoah") \
198 \
199 diagnostic(bool, ShenandoahAllowMixedAllocs, true, \
200 "Allow mixing mutator and collector allocations in a single " \
201 "region") \
202 \
203 experimental(uintx, ShenandoahAllocSpikeFactor, 5, \
204 "The amount of heap space to reserve for absorbing the " \
205 "allocation spikes. Larger value wastes more memory in " \
206 "non-emergency cases, but provides more safety in emergency " \
207 "cases. In percents of total heap size.") \
208 \
209 experimental(uintx, ShenandoahEvacReserve, 5, \
210 "Maximum amount of free space to reserve for evacuation. " \
211 "Larger values make GC more aggressive, while leaving less " \
212 "headroom for application to allocate in. " \
213 "In percents of total heap size.") \
214 \
215 experimental(double, ShenandoahEvacWaste, 1.2, \
216 "How much waste evacuations produce within the reserved " \
217 "space. Larger values make evacuations more resilient " \
218 "against allocation failures, at expense of smaller csets " \
219 "on each cycle.") \
220 \
221 experimental(bool, ShenandoahEvacReserveOverflow, true, \
222 "Allow evacuations to overflow the reserved space. " \
223 "Enabling it will make evacuations more resilient when " \
224 "evacuation reserve/waste is incorrect, at the risk that " \
225 "application allocations run out of memory too early.") \
226 \
227 diagnostic(bool, ShenandoahAllocationTrace, false, \
228 "Trace allocation latencies and stalls. Can be expensive when " \
229 "lots of allocations happen, and may introduce scalability " \
230 "bottlenecks.") \
231 \
232 diagnostic(intx, ShenandoahAllocationStallThreshold, 10000, \
233 "When allocation tracing is enabled, the allocation stalls " \
234 "larger than this threshold would be reported as warnings. " \
235 "Time is in microseconds.") \
236 \
237 experimental(uintx, ShenandoahEvacAssist, 10, \
238 "How many objects to evacuate on LRB assist path. " \
239 "Use zero to disable.") \
240 \
241 experimental(bool, ShenandoahPacing, true, \
242 "Pace application allocations to give GC chance to start " \
243 "and complete before allocation failure is reached.") \
244 \
245 experimental(uintx, ShenandoahPacingMaxDelay, 10, \
246 "Max delay for pacing application allocations. " \
247 "Time is in milliseconds.") \
248 \
249 experimental(uintx, ShenandoahPacingIdleSlack, 2, \
250 "Percent of heap counted as non-taxable allocations during idle. "\
251 "Larger value makes the pacing milder during idle phases, " \
252 "requiring less rendezvous with control thread. Lower value " \
253 "makes the pacing control less responsive to out-of-cycle allocs.")\
254 \
255 experimental(uintx, ShenandoahPacingCycleSlack, 10, \
256 "Percent of free space taken as non-taxable allocations during " \
257 "the GC cycle. Larger value makes the pacing milder at the " \
258 "beginning of the GC cycle. Lower value makes the pacing less " \
259 "uniform during the cycle.") \
260 \
261 experimental(double, ShenandoahPacingSurcharge, 1.1, \
262 "Additional pacing tax surcharge to help unclutter the heap. " \
263 "Larger values makes the pacing more aggressive. Lower values " \
264 "risk GC cycles finish with less memory than were available at " \
265 "the beginning of it.") \
266 \
267 experimental(uintx, ShenandoahCriticalFreeThreshold, 1, \
268 "Percent of heap that needs to be free after recovery cycles, " \
269 "either Degenerated or Full GC. If this much space is not " \
270 "available, next recovery step would triggered.") \
271 \
272 diagnostic(bool, ShenandoahDegeneratedGC, true, \
273 "Use Degenerated GC as the graceful degradation step. Disabling " \
274 "this leads to degradation to Full GC") \
275 \
276 experimental(uintx, ShenandoahFullGCThreshold, 3, \
277 "How many back-to-back Degenerated GCs to do before triggering " \
278 "a Full GC.") \
279 \
280 experimental(bool, ShenandoahImplicitGCInvokesConcurrent, false, \
281 "Should internally-caused GCs invoke concurrent cycles, or go to" \
282 "stop-the-world (degenerated/full)?") \
283 \
284 diagnostic(bool, ShenandoahHumongousMoves, true, \
285 "Allow moving humongous regions. This makes GC more resistant " \
286 "to external fragmentation that may otherwise fail other " \
287 "humongous allocations, at the expense of higher GC copying " \
288 "costs. Currently affects stop-the-world (full) cycle only.") \
289 \
290 diagnostic(bool, ShenandoahOOMDuringEvacALot, false, \
291 "Simulate OOM during evacuation frequently.") \
292 \
293 diagnostic(bool, ShenandoahAllocFailureALot, false, \
294 "Make lots of artificial allocation failures.") \
295 \
296 diagnostic(bool, ShenandoahTerminationTrace, false, \
297 "Tracing task termination timings") \
298 \
299 diagnostic(bool, ShenandoahAlwaysPreTouch, false, \
300 "Pre-touch heap memory, overrides global AlwaysPreTouch") \
301 \
302 experimental(intx, ShenandoahMarkScanPrefetch, 32, \
303 "How many objects to prefetch ahead when traversing mark bitmaps."\
304 "Set to 0 to disable prefetching.") \
305 \
306 experimental(uintx, ShenandoahMarkLoopStride, 1000, \
307 "How many items are processed during one marking step") \
308 \
309 experimental(uintx, ShenandoahParallelRegionStride, 1024, \
310 "How many regions are processed in one stride during parallel " \
311 "iteration.") \
312 \
313 experimental(intx, ShenandoahSATBBufferSize, 1 * K, \
314 "Number of entries in an SATB log buffer.") \
315 \
316 experimental(uintx, ShenandoahSATBBufferFlushInterval, 100, \
317 "Forcefully flush non-empty SATB buffers at this interval. " \
318 "Time is in milliseconds.") \
319 \
320 experimental(bool, ShenandoahPreclean, true, \
321 "Do concurrent preclean phase before final mark: process " \
322 "definitely alive references to avoid dealing with them during " \
323 "pause.") \
324 \
325 diagnostic(bool, ShenandoahSATBBarrier, true, \
326 "Turn on/off SATB barriers in Shenandoah") \
327 \
328 diagnostic(bool, ShenandoahKeepAliveBarrier, true, \
329 "Turn on/off keep alive barriers in Shenandoah") \
330 \
331 diagnostic(bool, ShenandoahStoreValEnqueueBarrier, false, \
332 "Turn on/off enqueuing of oops for storeval barriers") \
333 \
334 diagnostic(bool, ShenandoahCASBarrier, true, \
335 "Turn on/off CAS barriers in Shenandoah") \
336 \
337 diagnostic(bool, ShenandoahCloneBarrier, true, \
338 "Turn on/off clone barriers in Shenandoah") \
339 \
340 diagnostic(bool, ShenandoahLoadRefBarrier, true, \
341 "Turn on/off load-reference barriers in Shenandoah") \
342 \
343 experimental(bool, ShenandoahConcurrentScanCodeRoots, true, \
344 "Scan code roots concurrently, instead of during a pause") \
345 \
346 experimental(uintx, ShenandoahCodeRootsStyle, 2, \
347 "Use this style to scan code cache:" \
348 " 0 - sequential iterator;" \
349 " 1 - parallel iterator;" \
350 " 2 - parallel iterator with cset filters;") \
351 \
352 diagnostic(bool, ShenandoahOptimizeStaticFinals, true, \
353 "Optimize barriers on static final fields. " \
354 "Turn it off for maximum compatibility with reflection or JNI " \
355 "code that manipulates final fields.") \
356 \
357 experimental(bool, ShenandoahCommonGCStateLoads, false, \
358 "Enable commonming for GC state loads in generated code.") \
359 \
360 develop(bool, ShenandoahVerifyOptoBarriers, false, \
361 "Verify no missing barriers in c2") \
362 \
363 product(bool, ShenandoahLogTrace, false, \
364 "Turns on logging in Shenandoah at trace level. ") \
365 \
366 product(bool, ShenandoahLogDebug, false, \
367 "Turns on logging in Shenandoah at debug level. ") \
368 \
369 product(bool, ShenandoahLogInfo, false, \
370 "Turns on logging in Shenandoah at info level. ") \
371 \
372 product(bool, ShenandoahLogWarning, false, \
373 "Turns on logging in Shenandoah at warning level. ") \
374 \
375
376 SHENANDOAH_FLAGS(DECLARE_DEVELOPER_FLAG, \
377 DECLARE_PD_DEVELOPER_FLAG, \
378 DECLARE_PRODUCT_FLAG, \
379 DECLARE_PD_PRODUCT_FLAG, \
380 DECLARE_DIAGNOSTIC_FLAG, \
381 DECLARE_EXPERIMENTAL_FLAG, \
382 DECLARE_NOTPRODUCT_FLAG, \
383 DECLARE_MANAGEABLE_FLAG, \
384 DECLARE_PRODUCT_RW_FLAG)
385
386 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAH_GLOBALS_HPP