1 /*
2 * Copyright (c) 2003, 2018, 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 #include "gc/parallel/asPSYoungGen.hpp"
27 #include "gc/parallel/parallelScavengeHeap.hpp"
28 #include "gc/parallel/psMarkSweepDecorator.hpp"
29 #include "gc/parallel/psScavenge.inline.hpp"
30 #include "gc/parallel/psYoungGen.hpp"
31 #include "gc/shared/gcUtil.hpp"
32 #include "gc/shared/genArguments.hpp"
33 #include "gc/shared/spaceDecorator.inline.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "runtime/java.hpp"
36 #include "utilities/align.hpp"
37
38 ASPSYoungGen::ASPSYoungGen(size_t init_byte_size,
39 size_t minimum_byte_size,
40 size_t byte_size_limit) :
41 PSYoungGen(init_byte_size, minimum_byte_size, byte_size_limit),
42 _gen_size_limit(byte_size_limit) {
43 }
44
45
46 ASPSYoungGen::ASPSYoungGen(PSVirtualSpace* vs,
47 size_t init_byte_size,
48 size_t minimum_byte_size,
49 size_t byte_size_limit) :
50 //PSYoungGen(init_byte_size, minimum_byte_size, byte_size_limit),
51 PSYoungGen(vs->committed_size(), minimum_byte_size, byte_size_limit),
52 _gen_size_limit(byte_size_limit) {
53
54 assert(vs->committed_size() == init_byte_size, "Cannot replace with");
55
56 _virtual_space = vs;
57 }
58
59 void ASPSYoungGen::initialize_virtual_space(ReservedSpace rs,
60 size_t alignment) {
61 assert(_init_gen_size != 0, "Should have a finite size");
62 _virtual_space = new PSVirtualSpaceHighToLow(rs, alignment);
63 if (!_virtual_space->expand_by(_init_gen_size)) {
64 vm_exit_during_initialization("Could not reserve enough space for "
65 "object heap");
66 }
67 }
68
69 void ASPSYoungGen::initialize(ReservedSpace rs, size_t alignment) {
70 initialize_virtual_space(rs, alignment);
71 initialize_work();
72 }
73
74 size_t ASPSYoungGen::available_for_expansion() {
75 size_t current_committed_size = virtual_space()->committed_size();
76 assert((gen_size_limit() >= current_committed_size),
77 "generation size limit is wrong");
78
79 size_t result = gen_size_limit() - current_committed_size;
80 size_t result_aligned = align_down(result, GenAlignment);
81 return result_aligned;
82 }
83
84 // Return the number of bytes the young gen is willing give up.
85 //
86 // Future implementations could check the survivors and if to_space is in the
87 // right place (below from_space), take a chunk from to_space.
88 size_t ASPSYoungGen::available_for_contraction() {
89 size_t uncommitted_bytes = virtual_space()->uncommitted_size();
90 if (uncommitted_bytes != 0) {
91 return uncommitted_bytes;
92 }
93
94 if (eden_space()->is_empty()) {
95 // Respect the minimum size for eden and for the young gen as a whole.
96 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
97 const size_t eden_alignment = SpaceAlignment;
98
99 assert(eden_space()->capacity_in_bytes() >= eden_alignment,
100 "Alignment is wrong");
101 size_t eden_avail = eden_space()->capacity_in_bytes() - eden_alignment;
102 eden_avail = align_down(eden_avail, GenAlignment);
103
104 assert(virtual_space()->committed_size() >= min_gen_size(),
105 "minimum gen size is wrong");
106 size_t gen_avail = virtual_space()->committed_size() - min_gen_size();
107 assert(virtual_space()->is_aligned(gen_avail), "not aligned");
108
109 const size_t max_contraction = MIN2(eden_avail, gen_avail);
110 // See comment for ASPSOldGen::available_for_contraction()
111 // for reasons the "increment" fraction is used.
112 PSAdaptiveSizePolicy* policy = heap->size_policy();
113 size_t result = policy->eden_increment_aligned_down(max_contraction);
114 size_t result_aligned = align_down(result, GenAlignment);
115
116 log_trace(gc, ergo)("ASPSYoungGen::available_for_contraction: " SIZE_FORMAT " K", result_aligned/K);
117 log_trace(gc, ergo)(" max_contraction " SIZE_FORMAT " K", max_contraction/K);
118 log_trace(gc, ergo)(" eden_avail " SIZE_FORMAT " K", eden_avail/K);
119 log_trace(gc, ergo)(" gen_avail " SIZE_FORMAT " K", gen_avail/K);
120
121 return result_aligned;
122 }
123
124 return 0;
125 }
126
127 // The current implementation only considers to the end of eden.
128 // If to_space is below from_space, to_space is not considered.
129 // to_space can be.
130 size_t ASPSYoungGen::available_to_live() {
131 const size_t alignment = SpaceAlignment;
132
133 // Include any space that is committed but is not in eden.
134 size_t available = pointer_delta(eden_space()->bottom(),
135 virtual_space()->low(),
136 sizeof(char));
137
138 const size_t eden_capacity = eden_space()->capacity_in_bytes();
139 if (eden_space()->is_empty() && eden_capacity > alignment) {
140 available += eden_capacity - alignment;
141 }
142 return available;
143 }
144
145 // Similar to PSYoungGen::resize_generation() but
146 // allows sum of eden_size and 2 * survivor_size to exceed _max_gen_size
147 // expands at the low end of the virtual space
148 // moves the boundary between the generations in order to expand
149 // some additional diagnostics
150 // If no additional changes are required, this can be deleted
151 // and the changes factored back into PSYoungGen::resize_generation().
152 bool ASPSYoungGen::resize_generation(size_t eden_size, size_t survivor_size) {
153 const size_t alignment = virtual_space()->alignment();
154 size_t orig_size = virtual_space()->committed_size();
155 bool size_changed = false;
156
157 // There used to be a guarantee here that
158 // (eden_size + 2*survivor_size) <= _max_gen_size
159 // This requirement is enforced by the calculation of desired_size
160 // below. It may not be true on entry since the size of the
161 // eden_size is no bounded by the generation size.
162
163 assert(max_size() == reserved().byte_size(), "max gen size problem?");
164 assert(min_gen_size() <= orig_size && orig_size <= max_size(),
165 "just checking");
166
167 // Adjust new generation size
168 const size_t eden_plus_survivors =
169 align_up(eden_size + 2 * survivor_size, alignment);
170 size_t desired_size = MAX2(MIN2(eden_plus_survivors, gen_size_limit()),
171 min_gen_size());
172 assert(desired_size <= gen_size_limit(), "just checking");
173
174 if (desired_size > orig_size) {
175 // Grow the generation
176 size_t change = desired_size - orig_size;
177 HeapWord* prev_low = (HeapWord*) virtual_space()->low();
178 if (!virtual_space()->expand_by(change)) {
179 return false;
180 }
181 if (ZapUnusedHeapArea) {
182 // Mangle newly committed space immediately because it
183 // can be done here more simply that after the new
184 // spaces have been computed.
185 HeapWord* new_low = (HeapWord*) virtual_space()->low();
186 assert(new_low < prev_low, "Did not grow");
187
188 MemRegion mangle_region(new_low, prev_low);
189 SpaceMangler::mangle_region(mangle_region);
190 }
191 size_changed = true;
192 } else if (desired_size < orig_size) {
193 size_t desired_change = orig_size - desired_size;
194
195 // How much is available for shrinking.
196 size_t available_bytes = limit_gen_shrink(desired_change);
197 size_t change = MIN2(desired_change, available_bytes);
198 virtual_space()->shrink_by(change);
199 size_changed = true;
200 } else {
201 if (orig_size == gen_size_limit()) {
202 log_trace(gc)("ASPSYoung generation size at maximum: " SIZE_FORMAT "K", orig_size/K);
203 } else if (orig_size == min_gen_size()) {
204 log_trace(gc)("ASPSYoung generation size at minium: " SIZE_FORMAT "K", orig_size/K);
205 }
206 }
207
208 if (size_changed) {
209 reset_after_change();
210 log_trace(gc)("ASPSYoung generation size changed: " SIZE_FORMAT "K->" SIZE_FORMAT "K",
211 orig_size/K, virtual_space()->committed_size()/K);
212 }
213
214 guarantee(eden_plus_survivors <= virtual_space()->committed_size() ||
215 virtual_space()->committed_size() == max_size(), "Sanity");
216
217 return true;
218 }
219
220 // Similar to PSYoungGen::resize_spaces() but
221 // eden always starts at the low end of the committed virtual space
222 // current implementation does not allow holes between the spaces
223 // _young_generation_boundary has to be reset because it changes.
224 // so additional verification
225
226 void ASPSYoungGen::resize_spaces(size_t requested_eden_size,
227 size_t requested_survivor_size) {
228 assert(UseAdaptiveSizePolicy, "sanity check");
229 assert(requested_eden_size > 0 && requested_survivor_size > 0,
230 "just checking");
231
232 space_invariants();
233
234 // We require eden and to space to be empty
235 if ((!eden_space()->is_empty()) || (!to_space()->is_empty())) {
236 return;
237 }
238
239 log_trace(gc, ergo)("PSYoungGen::resize_spaces(requested_eden_size: "
240 SIZE_FORMAT
241 ", requested_survivor_size: " SIZE_FORMAT ")",
242 requested_eden_size, requested_survivor_size);
243 log_trace(gc, ergo)(" eden: [" PTR_FORMAT ".." PTR_FORMAT ") "
244 SIZE_FORMAT,
245 p2i(eden_space()->bottom()),
246 p2i(eden_space()->end()),
247 pointer_delta(eden_space()->end(), eden_space()->bottom(), sizeof(char)));
248 log_trace(gc, ergo)(" from: [" PTR_FORMAT ".." PTR_FORMAT ") "
249 SIZE_FORMAT,
250 p2i(from_space()->bottom()),
251 p2i(from_space()->end()),
252 pointer_delta(from_space()->end(), from_space()->bottom(), sizeof(char)));
253 log_trace(gc, ergo)(" to: [" PTR_FORMAT ".." PTR_FORMAT ") "
254 SIZE_FORMAT,
255 p2i(to_space()->bottom()),
256 p2i(to_space()->end()),
257 pointer_delta( to_space()->end(), to_space()->bottom(), sizeof(char)));
258
259 // There's nothing to do if the new sizes are the same as the current
260 if (requested_survivor_size == to_space()->capacity_in_bytes() &&
261 requested_survivor_size == from_space()->capacity_in_bytes() &&
262 requested_eden_size == eden_space()->capacity_in_bytes()) {
263 log_trace(gc, ergo)(" capacities are the right sizes, returning");
264 return;
265 }
266
267 char* eden_start = (char*)virtual_space()->low();
268 char* eden_end = (char*)eden_space()->end();
269 char* from_start = (char*)from_space()->bottom();
270 char* from_end = (char*)from_space()->end();
271 char* to_start = (char*)to_space()->bottom();
272 char* to_end = (char*)to_space()->end();
273
274 assert(eden_start < from_start, "Cannot push into from_space");
275
276 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
277 const bool maintain_minimum =
278 (requested_eden_size + 2 * requested_survivor_size) <= min_gen_size();
279
280 bool eden_from_to_order = from_start < to_start;
281 // Check whether from space is below to space
282 if (eden_from_to_order) {
283 // Eden, from, to
284
285 log_trace(gc, ergo)(" Eden, from, to:");
286
287 // Set eden
288 // "requested_eden_size" is a goal for the size of eden
289 // and may not be attainable. "eden_size" below is
290 // calculated based on the location of from-space and
291 // the goal for the size of eden. from-space is
292 // fixed in place because it contains live data.
293 // The calculation is done this way to avoid 32bit
294 // overflow (i.e., eden_start + requested_eden_size
295 // may too large for representation in 32bits).
296 size_t eden_size;
297 if (maintain_minimum) {
298 // Only make eden larger than the requested size if
299 // the minimum size of the generation has to be maintained.
300 // This could be done in general but policy at a higher
301 // level is determining a requested size for eden and that
302 // should be honored unless there is a fundamental reason.
303 eden_size = pointer_delta(from_start,
304 eden_start,
305 sizeof(char));
306 } else {
307 eden_size = MIN2(requested_eden_size,
308 pointer_delta(from_start, eden_start, sizeof(char)));
309 }
310
311 eden_end = eden_start + eden_size;
312 assert(eden_end >= eden_start, "addition overflowed");
313
314 // To may resize into from space as long as it is clear of live data.
315 // From space must remain page aligned, though, so we need to do some
316 // extra calculations.
317
318 // First calculate an optimal to-space
319 to_end = (char*)virtual_space()->high();
320 to_start = (char*)pointer_delta(to_end,
321 (char*)requested_survivor_size,
322 sizeof(char));
323
324 // Does the optimal to-space overlap from-space?
325 if (to_start < (char*)from_space()->end()) {
326 // Calculate the minimum offset possible for from_end
327 size_t from_size =
328 pointer_delta(from_space()->top(), from_start, sizeof(char));
329
330 // Should we be in this method if from_space is empty? Why not the set_space method? FIX ME!
331 if (from_size == 0) {
332 from_size = SpaceAlignment;
333 } else {
334 from_size = align_up(from_size, SpaceAlignment);
335 }
336
337 from_end = from_start + from_size;
338 assert(from_end > from_start, "addition overflow or from_size problem");
339
340 guarantee(from_end <= (char*)from_space()->end(),
341 "from_end moved to the right");
342
343 // Now update to_start with the new from_end
344 to_start = MAX2(from_end, to_start);
345 }
346
347 guarantee(to_start != to_end, "to space is zero sized");
348
349 log_trace(gc, ergo)(" [eden_start .. eden_end): "
350 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
351 p2i(eden_start),
352 p2i(eden_end),
353 pointer_delta(eden_end, eden_start, sizeof(char)));
354 log_trace(gc, ergo)(" [from_start .. from_end): "
355 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
356 p2i(from_start),
357 p2i(from_end),
358 pointer_delta(from_end, from_start, sizeof(char)));
359 log_trace(gc, ergo)(" [ to_start .. to_end): "
360 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
361 p2i(to_start),
362 p2i(to_end),
363 pointer_delta( to_end, to_start, sizeof(char)));
364 } else {
365 // Eden, to, from
366 log_trace(gc, ergo)(" Eden, to, from:");
367
368 // To space gets priority over eden resizing. Note that we position
369 // to space as if we were able to resize from space, even though from
370 // space is not modified.
371 // Giving eden priority was tried and gave poorer performance.
372 to_end = (char*)pointer_delta(virtual_space()->high(),
373 (char*)requested_survivor_size,
374 sizeof(char));
375 to_end = MIN2(to_end, from_start);
376 to_start = (char*)pointer_delta(to_end, (char*)requested_survivor_size,
377 sizeof(char));
378 // if the space sizes are to be increased by several times then
379 // 'to_start' will point beyond the young generation. In this case
380 // 'to_start' should be adjusted.
381 to_start = MAX2(to_start, eden_start + SpaceAlignment);
382
383 // Compute how big eden can be, then adjust end.
384 // See comments above on calculating eden_end.
385 size_t eden_size;
386 if (maintain_minimum) {
387 eden_size = pointer_delta(to_start, eden_start, sizeof(char));
388 } else {
389 eden_size = MIN2(requested_eden_size,
390 pointer_delta(to_start, eden_start, sizeof(char)));
391 }
392 eden_end = eden_start + eden_size;
393 assert(eden_end >= eden_start, "addition overflowed");
394
395 // Don't let eden shrink down to 0 or less.
396 eden_end = MAX2(eden_end, eden_start + SpaceAlignment);
397 to_start = MAX2(to_start, eden_end);
398
399 log_trace(gc, ergo)(" [eden_start .. eden_end): "
400 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
401 p2i(eden_start),
402 p2i(eden_end),
403 pointer_delta(eden_end, eden_start, sizeof(char)));
404 log_trace(gc, ergo)(" [ to_start .. to_end): "
405 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
406 p2i(to_start),
407 p2i(to_end),
408 pointer_delta( to_end, to_start, sizeof(char)));
409 log_trace(gc, ergo)(" [from_start .. from_end): "
410 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
411 p2i(from_start),
412 p2i(from_end),
413 pointer_delta(from_end, from_start, sizeof(char)));
414 }
415
416
417 guarantee((HeapWord*)from_start <= from_space()->bottom(),
418 "from start moved to the right");
419 guarantee((HeapWord*)from_end >= from_space()->top(),
420 "from end moved into live data");
421 assert(is_object_aligned(eden_start), "checking alignment");
422 assert(is_object_aligned(from_start), "checking alignment");
423 assert(is_object_aligned(to_start), "checking alignment");
424
425 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)eden_end);
426 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
427 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)from_end);
428
429 // Let's make sure the call to initialize doesn't reset "top"!
430 DEBUG_ONLY(HeapWord* old_from_top = from_space()->top();)
431
432 // For logging block below
433 size_t old_from = from_space()->capacity_in_bytes();
434 size_t old_to = to_space()->capacity_in_bytes();
435
436 if (ZapUnusedHeapArea) {
437 // NUMA is a special case because a numa space is not mangled
438 // in order to not prematurely bind its address to memory to
439 // the wrong memory (i.e., don't want the GC thread to first
440 // touch the memory). The survivor spaces are not numa
441 // spaces and are mangled.
442 if (UseNUMA) {
443 if (eden_from_to_order) {
444 mangle_survivors(from_space(), fromMR, to_space(), toMR);
445 } else {
446 mangle_survivors(to_space(), toMR, from_space(), fromMR);
447 }
448 }
449
450 // If not mangling the spaces, do some checking to verify that
451 // the spaces are already mangled.
452 // The spaces should be correctly mangled at this point so
453 // do some checking here. Note that they are not being mangled
454 // in the calls to initialize().
455 // Must check mangling before the spaces are reshaped. Otherwise,
456 // the bottom or end of one space may have moved into an area
457 // covered by another space and a failure of the check may
458 // not correctly indicate which space is not properly mangled.
459
460 HeapWord* limit = (HeapWord*) virtual_space()->high();
461 eden_space()->check_mangled_unused_area(limit);
462 from_space()->check_mangled_unused_area(limit);
463 to_space()->check_mangled_unused_area(limit);
464 }
465 // When an existing space is being initialized, it is not
466 // mangled because the space has been previously mangled.
467 eden_space()->initialize(edenMR,
468 SpaceDecorator::Clear,
469 SpaceDecorator::DontMangle);
470 to_space()->initialize(toMR,
471 SpaceDecorator::Clear,
472 SpaceDecorator::DontMangle);
473 from_space()->initialize(fromMR,
474 SpaceDecorator::DontClear,
475 SpaceDecorator::DontMangle);
476
477 PSScavenge::set_young_generation_boundary(eden_space()->bottom());
478
479 assert(from_space()->top() == old_from_top, "from top changed!");
480
481 log_trace(gc, ergo)("AdaptiveSizePolicy::survivor space sizes: "
482 "collection: %d "
483 "(" SIZE_FORMAT ", " SIZE_FORMAT ") -> "
484 "(" SIZE_FORMAT ", " SIZE_FORMAT ") ",
485 ParallelScavengeHeap::heap()->total_collections(),
486 old_from, old_to,
487 from_space()->capacity_in_bytes(),
488 to_space()->capacity_in_bytes());
489
490 space_invariants();
491 }
492 void ASPSYoungGen::reset_after_change() {
493 assert_locked_or_safepoint(Heap_lock);
494
495 _reserved = MemRegion((HeapWord*)virtual_space()->low_boundary(),
496 (HeapWord*)virtual_space()->high_boundary());
497 PSScavenge::set_subject_to_discovery_span(_reserved);
498
499 HeapWord* new_eden_bottom = (HeapWord*)virtual_space()->low();
500 HeapWord* eden_bottom = eden_space()->bottom();
501 if (new_eden_bottom != eden_bottom) {
502 MemRegion eden_mr(new_eden_bottom, eden_space()->end());
503 eden_space()->initialize(eden_mr,
504 SpaceDecorator::Clear,
505 SpaceDecorator::Mangle);
506 PSScavenge::set_young_generation_boundary(eden_space()->bottom());
507 }
508 MemRegion cmr((HeapWord*)virtual_space()->low(),
509 (HeapWord*)virtual_space()->high());
510 ParallelScavengeHeap::heap()->barrier_set()->card_table()->resize_covered_region(cmr);
511
512 space_invariants();
513 }