Mon, 12 Mar 2012 14:59:00 -0700
7147724: G1: hang in SurrogateLockerThread::manipulatePLL
Summary: Attempting to initiate a marking cycle when allocating a humongous object can, if a marking cycle is successfully initiated by another thread, result in the allocating thread spinning until the marking cycle is complete. Eliminate a deadlock between the main ConcurrentMarkThread, the SurrogateLocker thread, the VM thread, and a mutator thread waiting on the SecondaryFreeList_lock (while free regions are going to become available) by not manipulating the pending list lock during the prologue and epilogue of the cleanup pause.
Reviewed-by: brutisso, jcoomes, tonyp
1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/collectionSetChooser.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
28 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
29 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
30 #include "memory/space.inline.hpp"
32 CSetChooserCache::CSetChooserCache() {
33 for (int i = 0; i < CacheLength; ++i)
34 _cache[i] = NULL;
35 clear();
36 }
38 void CSetChooserCache::clear() {
39 _occupancy = 0;
40 _first = 0;
41 for (int i = 0; i < CacheLength; ++i) {
42 HeapRegion *hr = _cache[i];
43 if (hr != NULL)
44 hr->set_sort_index(-1);
45 _cache[i] = NULL;
46 }
47 }
49 #ifndef PRODUCT
50 bool CSetChooserCache::verify() {
51 guarantee(false, "CSetChooserCache::verify(): don't call this any more");
53 int index = _first;
54 HeapRegion *prev = NULL;
55 for (int i = 0; i < _occupancy; ++i) {
56 guarantee(_cache[index] != NULL, "cache entry should not be empty");
57 HeapRegion *hr = _cache[index];
58 guarantee(!hr->is_young(), "should not be young!");
59 if (prev != NULL) {
60 guarantee(prev->gc_efficiency() >= hr->gc_efficiency(),
61 "cache should be correctly ordered");
62 }
63 guarantee(hr->sort_index() == get_sort_index(index),
64 "sort index should be correct");
65 index = trim_index(index + 1);
66 prev = hr;
67 }
69 for (int i = 0; i < (CacheLength - _occupancy); ++i) {
70 guarantee(_cache[index] == NULL, "cache entry should be empty");
71 index = trim_index(index + 1);
72 }
74 guarantee(index == _first, "we should have reached where we started from");
75 return true;
76 }
77 #endif // PRODUCT
79 void CSetChooserCache::insert(HeapRegion *hr) {
80 guarantee(false, "CSetChooserCache::insert(): don't call this any more");
82 assert(!is_full(), "cache should not be empty");
83 hr->calc_gc_efficiency();
85 int empty_index;
86 if (_occupancy == 0) {
87 empty_index = _first;
88 } else {
89 empty_index = trim_index(_first + _occupancy);
90 assert(_cache[empty_index] == NULL, "last slot should be empty");
91 int last_index = trim_index(empty_index - 1);
92 HeapRegion *last = _cache[last_index];
93 assert(last != NULL,"as the cache is not empty, last should not be empty");
94 while (empty_index != _first &&
95 last->gc_efficiency() < hr->gc_efficiency()) {
96 _cache[empty_index] = last;
97 last->set_sort_index(get_sort_index(empty_index));
98 empty_index = last_index;
99 last_index = trim_index(last_index - 1);
100 last = _cache[last_index];
101 }
102 }
103 _cache[empty_index] = hr;
104 hr->set_sort_index(get_sort_index(empty_index));
106 ++_occupancy;
107 assert(verify(), "cache should be consistent");
108 }
110 HeapRegion *CSetChooserCache::remove_first() {
111 guarantee(false, "CSetChooserCache::remove_first(): "
112 "don't call this any more");
114 if (_occupancy > 0) {
115 assert(_cache[_first] != NULL, "cache should have at least one region");
116 HeapRegion *ret = _cache[_first];
117 _cache[_first] = NULL;
118 ret->set_sort_index(-1);
119 --_occupancy;
120 _first = trim_index(_first + 1);
121 assert(verify(), "cache should be consistent");
122 return ret;
123 } else {
124 return NULL;
125 }
126 }
128 // Even though we don't use the GC efficiency in our heuristics as
129 // much as we used to, we still order according to GC efficiency. This
130 // will cause regions with a lot of live objects and large RSets to
131 // end up at the end of the array. Given that we might skip collecting
132 // the last few old regions, if after a few mixed GCs the remaining
133 // have reclaimable bytes under a certain threshold, the hope is that
134 // the ones we'll skip are ones with both large RSets and a lot of
135 // live objects, not the ones with just a lot of live objects if we
136 // ordered according to the amount of reclaimable bytes per region.
137 static int orderRegions(HeapRegion* hr1, HeapRegion* hr2) {
138 if (hr1 == NULL) {
139 if (hr2 == NULL) {
140 return 0;
141 } else {
142 return 1;
143 }
144 } else if (hr2 == NULL) {
145 return -1;
146 }
148 double gc_eff1 = hr1->gc_efficiency();
149 double gc_eff2 = hr2->gc_efficiency();
150 if (gc_eff1 > gc_eff2) {
151 return -1;
152 } if (gc_eff1 < gc_eff2) {
153 return 1;
154 } else {
155 return 0;
156 }
157 }
159 static int orderRegions(HeapRegion** hr1p, HeapRegion** hr2p) {
160 return orderRegions(*hr1p, *hr2p);
161 }
163 CollectionSetChooser::CollectionSetChooser() :
164 // The line below is the worst bit of C++ hackery I've ever written
165 // (Detlefs, 11/23). You should think of it as equivalent to
166 // "_regions(100, true)": initialize the growable array and inform it
167 // that it should allocate its elem array(s) on the C heap.
168 //
169 // The first argument, however, is actually a comma expression
170 // (set_allocation_type(this, C_HEAP), 100). The purpose of the
171 // set_allocation_type() call is to replace the default allocation
172 // type for embedded objects STACK_OR_EMBEDDED with C_HEAP. It will
173 // allow to pass the assert in GenericGrowableArray() which checks
174 // that a growable array object must be on C heap if elements are.
175 //
176 // Note: containing object is allocated on C heap since it is CHeapObj.
177 //
178 _markedRegions((ResourceObj::set_allocation_type((address)&_markedRegions,
179 ResourceObj::C_HEAP),
180 100), true /* C_Heap */),
181 _curr_index(0), _length(0),
182 _regionLiveThresholdBytes(0), _remainingReclaimableBytes(0),
183 _first_par_unreserved_idx(0) {
184 _regionLiveThresholdBytes =
185 HeapRegion::GrainBytes * (size_t) G1OldCSetRegionLiveThresholdPercent / 100;
186 }
188 #ifndef PRODUCT
189 bool CollectionSetChooser::verify() {
190 guarantee(_length >= 0, err_msg("_length: %d", _length));
191 guarantee(0 <= _curr_index && _curr_index <= _length,
192 err_msg("_curr_index: %d _length: %d", _curr_index, _length));
193 int index = 0;
194 size_t sum_of_reclaimable_bytes = 0;
195 while (index < _curr_index) {
196 guarantee(_markedRegions.at(index) == NULL,
197 "all entries before _curr_index should be NULL");
198 index += 1;
199 }
200 HeapRegion *prev = NULL;
201 while (index < _length) {
202 HeapRegion *curr = _markedRegions.at(index++);
203 guarantee(curr != NULL, "Regions in _markedRegions array cannot be NULL");
204 int si = curr->sort_index();
205 guarantee(!curr->is_young(), "should not be young!");
206 guarantee(!curr->isHumongous(), "should not be humongous!");
207 guarantee(si > -1 && si == (index-1), "sort index invariant");
208 if (prev != NULL) {
209 guarantee(orderRegions(prev, curr) != 1,
210 err_msg("GC eff prev: %1.4f GC eff curr: %1.4f",
211 prev->gc_efficiency(), curr->gc_efficiency()));
212 }
213 sum_of_reclaimable_bytes += curr->reclaimable_bytes();
214 prev = curr;
215 }
216 guarantee(sum_of_reclaimable_bytes == _remainingReclaimableBytes,
217 err_msg("reclaimable bytes inconsistent, "
218 "remaining: "SIZE_FORMAT" sum: "SIZE_FORMAT,
219 _remainingReclaimableBytes, sum_of_reclaimable_bytes));
220 return true;
221 }
222 #endif
224 void CollectionSetChooser::fillCache() {
225 guarantee(false, "fillCache: don't call this any more");
227 while (!_cache.is_full() && (_curr_index < _length)) {
228 HeapRegion* hr = _markedRegions.at(_curr_index);
229 assert(hr != NULL,
230 err_msg("Unexpected NULL hr in _markedRegions at index %d",
231 _curr_index));
232 _curr_index += 1;
233 assert(!hr->is_young(), "should not be young!");
234 assert(hr->sort_index() == _curr_index-1, "sort_index invariant");
235 _markedRegions.at_put(hr->sort_index(), NULL);
236 _cache.insert(hr);
237 assert(!_cache.is_empty(), "cache should not be empty");
238 }
239 assert(verify(), "cache should be consistent");
240 }
242 void CollectionSetChooser::sortMarkedHeapRegions() {
243 // First trim any unused portion of the top in the parallel case.
244 if (_first_par_unreserved_idx > 0) {
245 if (G1PrintParCleanupStats) {
246 gclog_or_tty->print(" Truncating _markedRegions from %d to %d.\n",
247 _markedRegions.length(), _first_par_unreserved_idx);
248 }
249 assert(_first_par_unreserved_idx <= _markedRegions.length(),
250 "Or we didn't reserved enough length");
251 _markedRegions.trunc_to(_first_par_unreserved_idx);
252 }
253 _markedRegions.sort(orderRegions);
254 assert(_length <= _markedRegions.length(), "Requirement");
255 assert(_length == 0 || _markedRegions.at(_length - 1) != NULL,
256 "Testing _length");
257 assert(_length == _markedRegions.length() ||
258 _markedRegions.at(_length) == NULL, "Testing _length");
259 if (G1PrintParCleanupStats) {
260 gclog_or_tty->print_cr(" Sorted %d marked regions.", _length);
261 }
262 for (int i = 0; i < _length; i++) {
263 assert(_markedRegions.at(i) != NULL, "Should be true by sorting!");
264 _markedRegions.at(i)->set_sort_index(i);
265 }
266 if (G1PrintRegionLivenessInfo) {
267 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Sorting");
268 for (int i = 0; i < _length; ++i) {
269 HeapRegion* r = _markedRegions.at(i);
270 cl.doHeapRegion(r);
271 }
272 }
273 assert(verify(), "CSet chooser verification");
274 }
276 size_t CollectionSetChooser::calcMinOldCSetLength() {
277 // The min old CSet region bound is based on the maximum desired
278 // number of mixed GCs after a cycle. I.e., even if some old regions
279 // look expensive, we should add them to the CSet anyway to make
280 // sure we go through the available old regions in no more than the
281 // maximum desired number of mixed GCs.
282 //
283 // The calculation is based on the number of marked regions we added
284 // to the CSet chooser in the first place, not how many remain, so
285 // that the result is the same during all mixed GCs that follow a cycle.
287 const size_t region_num = (size_t) _length;
288 const size_t gc_num = (size_t) G1MaxMixedGCNum;
289 size_t result = region_num / gc_num;
290 // emulate ceiling
291 if (result * gc_num < region_num) {
292 result += 1;
293 }
294 return result;
295 }
297 size_t CollectionSetChooser::calcMaxOldCSetLength() {
298 // The max old CSet region bound is based on the threshold expressed
299 // as a percentage of the heap size. I.e., it should bound the
300 // number of old regions added to the CSet irrespective of how many
301 // of them are available.
303 G1CollectedHeap* g1h = G1CollectedHeap::heap();
304 const size_t region_num = g1h->n_regions();
305 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
306 size_t result = region_num * perc / 100;
307 // emulate ceiling
308 if (100 * result < region_num * perc) {
309 result += 1;
310 }
311 return result;
312 }
314 void CollectionSetChooser::addMarkedHeapRegion(HeapRegion* hr) {
315 assert(!hr->isHumongous(),
316 "Humongous regions shouldn't be added to the collection set");
317 assert(!hr->is_young(), "should not be young!");
318 _markedRegions.append(hr);
319 _length++;
320 _remainingReclaimableBytes += hr->reclaimable_bytes();
321 hr->calc_gc_efficiency();
322 }
324 void CollectionSetChooser::prepareForAddMarkedHeapRegionsPar(size_t n_regions,
325 size_t chunkSize) {
326 _first_par_unreserved_idx = 0;
327 int n_threads = ParallelGCThreads;
328 if (UseDynamicNumberOfGCThreads) {
329 assert(G1CollectedHeap::heap()->workers()->active_workers() > 0,
330 "Should have been set earlier");
331 // This is defensive code. As the assertion above says, the number
332 // of active threads should be > 0, but in case there is some path
333 // or some improperly initialized variable with leads to no
334 // active threads, protect against that in a product build.
335 n_threads = MAX2(G1CollectedHeap::heap()->workers()->active_workers(),
336 1U);
337 }
338 size_t max_waste = n_threads * chunkSize;
339 // it should be aligned with respect to chunkSize
340 size_t aligned_n_regions =
341 (n_regions + (chunkSize - 1)) / chunkSize * chunkSize;
342 assert( aligned_n_regions % chunkSize == 0, "should be aligned" );
343 _markedRegions.at_put_grow((int)(aligned_n_regions + max_waste - 1), NULL);
344 }
346 jint CollectionSetChooser::getParMarkedHeapRegionChunk(jint n_regions) {
347 // Don't do this assert because this can be called at a point
348 // where the loop up stream will not execute again but might
349 // try to claim more chunks (loop test has not been done yet).
350 // assert(_markedRegions.length() > _first_par_unreserved_idx,
351 // "Striding beyond the marked regions");
352 jint res = Atomic::add(n_regions, &_first_par_unreserved_idx);
353 assert(_markedRegions.length() > res + n_regions - 1,
354 "Should already have been expanded");
355 return res - n_regions;
356 }
358 void CollectionSetChooser::setMarkedHeapRegion(jint index, HeapRegion* hr) {
359 assert(_markedRegions.at(index) == NULL, "precondition");
360 assert(!hr->is_young(), "should not be young!");
361 _markedRegions.at_put(index, hr);
362 hr->calc_gc_efficiency();
363 }
365 void CollectionSetChooser::updateTotals(jint region_num,
366 size_t reclaimable_bytes) {
367 // Only take the lock if we actually need to update the totals.
368 if (region_num > 0) {
369 assert(reclaimable_bytes > 0, "invariant");
370 // We could have just used atomics instead of taking the
371 // lock. However, we currently don't have an atomic add for size_t.
372 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
373 _length += (int) region_num;
374 _remainingReclaimableBytes += reclaimable_bytes;
375 } else {
376 assert(reclaimable_bytes == 0, "invariant");
377 }
378 }
380 void CollectionSetChooser::clearMarkedHeapRegions() {
381 for (int i = 0; i < _markedRegions.length(); i++) {
382 HeapRegion* r = _markedRegions.at(i);
383 if (r != NULL) {
384 r->set_sort_index(-1);
385 }
386 }
387 _markedRegions.clear();
388 _curr_index = 0;
389 _length = 0;
390 _remainingReclaimableBytes = 0;
391 };