1 /*
2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
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).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "memory/blockOffsetTable.inline.hpp"
28 #include "memory/cardGeneration.inline.hpp"
29 #include "memory/gcLocker.hpp"
30 #include "memory/generationSpec.hpp"
31 #include "memory/genOopClosures.inline.hpp"
32 #include "memory/genRemSet.hpp"
33 #include "memory/iterator.hpp"
34 #include "memory/memRegion.hpp"
35 #include "memory/space.inline.hpp"
36 #include "runtime/java.hpp"
37
38 CardGeneration::CardGeneration(ReservedSpace rs, size_t initial_byte_size,
39 int level,
40 GenRemSet* remset) :
41 Generation(rs, initial_byte_size, level), _rs(remset),
42 _shrink_factor(0), _min_heap_delta_bytes(), _capacity_at_prologue(),
43 _used_at_prologue()
44 {
45 HeapWord* start = (HeapWord*)rs.base();
46 size_t reserved_byte_size = rs.size();
47 assert((uintptr_t(start) & 3) == 0, "bad alignment");
48 assert((reserved_byte_size & 3) == 0, "bad alignment");
49 MemRegion reserved_mr(start, heap_word_size(reserved_byte_size));
50 _bts = new BlockOffsetSharedArray(reserved_mr,
51 heap_word_size(initial_byte_size));
52 MemRegion committed_mr(start, heap_word_size(initial_byte_size));
53 _rs->resize_covered_region(committed_mr);
54 if (_bts == NULL)
55 vm_exit_during_initialization("Could not allocate a BlockOffsetArray");
56
57 // Verify that the start and end of this generation is the start of a card.
58 // If this wasn't true, a single card could span more than on generation,
59 // which would cause problems when we commit/uncommit memory, and when we
60 // clear and dirty cards.
61 guarantee(_rs->is_aligned(reserved_mr.start()), "generation must be card aligned");
62 if (reserved_mr.end() != Universe::heap()->reserved_region().end()) {
63 // Don't check at the very end of the heap as we'll assert that we're probing off
64 // the end if we try.
65 guarantee(_rs->is_aligned(reserved_mr.end()), "generation must be card aligned");
66 }
67 _min_heap_delta_bytes = MinHeapDeltaBytes;
68 _capacity_at_prologue = initial_byte_size;
69 _used_at_prologue = 0;
70 }
71
72 bool CardGeneration::grow_by(size_t bytes) {
73 assert_correct_size_change_locking();
74 bool result = _virtual_space.expand_by(bytes);
75 if (result) {
76 size_t new_word_size =
77 heap_word_size(_virtual_space.committed_size());
78 MemRegion mr(space()->bottom(), new_word_size);
79 // Expand card table
80 Universe::heap()->barrier_set()->resize_covered_region(mr);
81 // Expand shared block offset array
82 _bts->resize(new_word_size);
83
84 // Fix for bug #4668531
85 if (ZapUnusedHeapArea) {
86 MemRegion mangle_region(space()->end(),
87 (HeapWord*)_virtual_space.high());
88 SpaceMangler::mangle_region(mangle_region);
89 }
90
91 // Expand space -- also expands space's BOT
92 // (which uses (part of) shared array above)
93 space()->set_end((HeapWord*)_virtual_space.high());
94
95 // update the space and generation capacity counters
96 update_counters();
97
98 if (Verbose && PrintGC) {
99 size_t new_mem_size = _virtual_space.committed_size();
100 size_t old_mem_size = new_mem_size - bytes;
101 gclog_or_tty->print_cr("Expanding %s from " SIZE_FORMAT "K by "
102 SIZE_FORMAT "K to " SIZE_FORMAT "K",
103 name(), old_mem_size/K, bytes/K, new_mem_size/K);
104 }
105 }
106 return result;
107 }
108
109 bool CardGeneration::expand(size_t bytes, size_t expand_bytes) {
110 assert_locked_or_safepoint(Heap_lock);
111 if (bytes == 0) {
112 return true; // That's what grow_by(0) would return
113 }
114 size_t aligned_bytes = ReservedSpace::page_align_size_up(bytes);
115 if (aligned_bytes == 0){
116 // The alignment caused the number of bytes to wrap. An expand_by(0) will
117 // return true with the implication that an expansion was done when it
118 // was not. A call to expand implies a best effort to expand by "bytes"
119 // but not a guarantee. Align down to give a best effort. This is likely
120 // the most that the generation can expand since it has some capacity to
121 // start with.
122 aligned_bytes = ReservedSpace::page_align_size_down(bytes);
123 }
124 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
125 bool success = false;
126 if (aligned_expand_bytes > aligned_bytes) {
127 success = grow_by(aligned_expand_bytes);
128 }
129 if (!success) {
130 success = grow_by(aligned_bytes);
131 }
132 if (!success) {
133 success = grow_to_reserved();
134 }
135 if (PrintGC && Verbose) {
136 if (success && GC_locker::is_active_and_needs_gc()) {
137 gclog_or_tty->print_cr("Garbage collection disabled, expanded heap instead");
138 }
139 }
140
141 return success;
142 }
143
144 bool CardGeneration::grow_to_reserved() {
145 assert_correct_size_change_locking();
146 bool success = true;
147 const size_t remaining_bytes = _virtual_space.uncommitted_size();
148 if (remaining_bytes > 0) {
149 success = grow_by(remaining_bytes);
150 DEBUG_ONLY(if (!success) warning("grow to reserved failed");)
151 }
152 return success;
153 }
154
155 void CardGeneration::shrink(size_t bytes) {
156 assert_correct_size_change_locking();
157
158 size_t size = ReservedSpace::page_align_size_down(bytes);
159 if (size == 0) {
160 return;
161 }
162
163 // Shrink committed space
164 _virtual_space.shrink_by(size);
165 // Shrink space; this also shrinks the space's BOT
166 space()->set_end((HeapWord*) _virtual_space.high());
167 size_t new_word_size = heap_word_size(space()->capacity());
168 // Shrink the shared block offset array
169 _bts->resize(new_word_size);
170 MemRegion mr(space()->bottom(), new_word_size);
171 // Shrink the card table
172 Universe::heap()->barrier_set()->resize_covered_region(mr);
173
174 if (Verbose && PrintGC) {
175 size_t new_mem_size = _virtual_space.committed_size();
176 size_t old_mem_size = new_mem_size + size;
177 gclog_or_tty->print_cr("Shrinking %s from " SIZE_FORMAT "K to " SIZE_FORMAT "K",
178 name(), old_mem_size/K, new_mem_size/K);
179 }
180 }
181
182 // No young generation references, clear this generation's cards.
183 void CardGeneration::clear_remembered_set() {
184 _rs->clear(reserved());
185 }
186
187
188 // Objects in this generation may have moved, invalidate this
189 // generation's cards.
190 void CardGeneration::invalidate_remembered_set() {
191 _rs->invalidate(used_region());
192 }
193
194
195 void CardGeneration::compute_new_size() {
196 assert(_shrink_factor <= 100, "invalid shrink factor");
197 size_t current_shrink_factor = _shrink_factor;
198 _shrink_factor = 0;
199
200 // We don't have floating point command-line arguments
201 // Note: argument processing ensures that MinHeapFreeRatio < 100.
202 const double minimum_free_percentage = MinHeapFreeRatio / 100.0;
203 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
204
205 // Compute some numbers about the state of the heap.
206 const size_t used_after_gc = used();
207 const size_t capacity_after_gc = capacity();
208
209 const double min_tmp = used_after_gc / maximum_used_percentage;
210 size_t minimum_desired_capacity = (size_t)MIN2(min_tmp, double(max_uintx));
211 // Don't shrink less than the initial generation size
212 minimum_desired_capacity = MAX2(minimum_desired_capacity,
213 spec()->init_size());
214 assert(used_after_gc <= minimum_desired_capacity, "sanity check");
215
216 if (PrintGC && Verbose) {
217 const size_t free_after_gc = free();
218 const double free_percentage = ((double)free_after_gc) / capacity_after_gc;
219 gclog_or_tty->print_cr("TenuredGeneration::compute_new_size: ");
220 gclog_or_tty->print_cr(" "
221 " minimum_free_percentage: %6.2f"
222 " maximum_used_percentage: %6.2f",
223 minimum_free_percentage,
224 maximum_used_percentage);
225 gclog_or_tty->print_cr(" "
226 " free_after_gc : %6.1fK"
227 " used_after_gc : %6.1fK"
228 " capacity_after_gc : %6.1fK",
229 free_after_gc / (double) K,
230 used_after_gc / (double) K,
231 capacity_after_gc / (double) K);
232 gclog_or_tty->print_cr(" "
233 " free_percentage: %6.2f",
234 free_percentage);
235 }
236
237 if (capacity_after_gc < minimum_desired_capacity) {
238 // If we have less free space than we want then expand
239 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
240 // Don't expand unless it's significant
241 if (expand_bytes >= _min_heap_delta_bytes) {
242 expand(expand_bytes, 0); // safe if expansion fails
243 }
244 if (PrintGC && Verbose) {
245 gclog_or_tty->print_cr(" expanding:"
246 " minimum_desired_capacity: %6.1fK"
247 " expand_bytes: %6.1fK"
248 " _min_heap_delta_bytes: %6.1fK",
249 minimum_desired_capacity / (double) K,
250 expand_bytes / (double) K,
251 _min_heap_delta_bytes / (double) K);
252 }
253 return;
254 }
255
256 // No expansion, now see if we want to shrink
257 size_t shrink_bytes = 0;
258 // We would never want to shrink more than this
259 size_t max_shrink_bytes = capacity_after_gc - minimum_desired_capacity;
260
261 if (MaxHeapFreeRatio < 100) {
262 const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;
263 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
264 const double max_tmp = used_after_gc / minimum_used_percentage;
265 size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));
266 maximum_desired_capacity = MAX2(maximum_desired_capacity,
267 spec()->init_size());
268 if (PrintGC && Verbose) {
269 gclog_or_tty->print_cr(" "
270 " maximum_free_percentage: %6.2f"
271 " minimum_used_percentage: %6.2f",
272 maximum_free_percentage,
273 minimum_used_percentage);
274 gclog_or_tty->print_cr(" "
275 " _capacity_at_prologue: %6.1fK"
276 " minimum_desired_capacity: %6.1fK"
277 " maximum_desired_capacity: %6.1fK",
278 _capacity_at_prologue / (double) K,
279 minimum_desired_capacity / (double) K,
280 maximum_desired_capacity / (double) K);
281 }
282 assert(minimum_desired_capacity <= maximum_desired_capacity,
283 "sanity check");
284
285 if (capacity_after_gc > maximum_desired_capacity) {
286 // Capacity too large, compute shrinking size
287 shrink_bytes = capacity_after_gc - maximum_desired_capacity;
288 // We don't want shrink all the way back to initSize if people call
289 // System.gc(), because some programs do that between "phases" and then
290 // we'd just have to grow the heap up again for the next phase. So we
291 // damp the shrinking: 0% on the first call, 10% on the second call, 40%
292 // on the third call, and 100% by the fourth call. But if we recompute
293 // size without shrinking, it goes back to 0%.
294 shrink_bytes = shrink_bytes / 100 * current_shrink_factor;
295 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
296 if (current_shrink_factor == 0) {
297 _shrink_factor = 10;
298 } else {
299 _shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);
300 }
301 if (PrintGC && Verbose) {
302 gclog_or_tty->print_cr(" "
303 " shrinking:"
304 " initSize: %.1fK"
305 " maximum_desired_capacity: %.1fK",
306 spec()->init_size() / (double) K,
307 maximum_desired_capacity / (double) K);
308 gclog_or_tty->print_cr(" "
309 " shrink_bytes: %.1fK"
310 " current_shrink_factor: " SIZE_FORMAT
311 " new shrink factor: " SIZE_FORMAT
312 " _min_heap_delta_bytes: %.1fK",
313 shrink_bytes / (double) K,
314 current_shrink_factor,
315 _shrink_factor,
316 _min_heap_delta_bytes / (double) K);
317 }
318 }
319 }
320
321 if (capacity_after_gc > _capacity_at_prologue) {
322 // We might have expanded for promotions, in which case we might want to
323 // take back that expansion if there's room after GC. That keeps us from
324 // stretching the heap with promotions when there's plenty of room.
325 size_t expansion_for_promotion = capacity_after_gc - _capacity_at_prologue;
326 expansion_for_promotion = MIN2(expansion_for_promotion, max_shrink_bytes);
327 // We have two shrinking computations, take the largest
328 shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);
329 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
330 if (PrintGC && Verbose) {
331 gclog_or_tty->print_cr(" "
332 " aggressive shrinking:"
333 " _capacity_at_prologue: %.1fK"
334 " capacity_after_gc: %.1fK"
335 " expansion_for_promotion: %.1fK"
336 " shrink_bytes: %.1fK",
337 capacity_after_gc / (double) K,
338 _capacity_at_prologue / (double) K,
339 expansion_for_promotion / (double) K,
340 shrink_bytes / (double) K);
341 }
342 }
343 // Don't shrink unless it's significant
344 if (shrink_bytes >= _min_heap_delta_bytes) {
345 shrink(shrink_bytes);
346 }
347 }
348
349 // Currently nothing to do.
350 void CardGeneration::prepare_for_verify() {}
351
352 void CardGeneration::space_iterate(SpaceClosure* blk,
353 bool usedOnly) {
354 blk->do_space(space());
355 }
356
357 void CardGeneration::younger_refs_iterate(OopsInGenClosure* blk) {
358 blk->set_generation(this);
359 younger_refs_in_space_iterate(space(), blk);
360 blk->reset_generation();
361 }