1 /*
2 * Copyright (c) 2003, 2020, 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/psScavenge.inline.hpp"
29 #include "gc/parallel/psYoungGen.hpp"
30 #include "gc/shared/gcUtil.hpp"
31 #include "gc/shared/genArguments.hpp"
32 #include "gc/shared/spaceDecorator.inline.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/java.hpp"
35 #include "utilities/align.hpp"
36
37 ASPSYoungGen::ASPSYoungGen(size_t init_byte_size,
38 size_t minimum_byte_size,
39 size_t byte_size_limit) :
40 PSYoungGen(init_byte_size, minimum_byte_size, byte_size_limit),
41 _gen_size_limit(byte_size_limit) {
42 }
43
44
45 ASPSYoungGen::ASPSYoungGen(PSVirtualSpace* vs,
46 size_t init_byte_size,
47 size_t minimum_byte_size,
48 size_t byte_size_limit) :
49 //PSYoungGen(init_byte_size, minimum_byte_size, byte_size_limit),
50 PSYoungGen(vs->committed_size(), minimum_byte_size, byte_size_limit),
51 _gen_size_limit(byte_size_limit) {
52
53 assert(vs->committed_size() == init_byte_size, "Cannot replace with");
54
55 _virtual_space = vs;
56 }
57
58 void ASPSYoungGen::initialize_virtual_space(ReservedSpace rs,
59 size_t alignment) {
60 assert(_init_gen_size != 0, "Should have a finite size");
61 _virtual_space = new PSVirtualSpaceHighToLow(rs, alignment);
62 if (!_virtual_space->expand_by(_init_gen_size)) {
63 vm_exit_during_initialization("Could not reserve enough space for "
64 "object heap");
65 }
66 }
67
68 void ASPSYoungGen::initialize(ReservedSpace rs, size_t alignment) {
69 initialize_virtual_space(rs, alignment);
70 initialize_work();
71 }
72
73 size_t ASPSYoungGen::available_for_expansion() {
74 size_t current_committed_size = virtual_space()->committed_size();
75 assert((gen_size_limit() >= current_committed_size),
76 "generation size limit is wrong");
77
78 size_t result = gen_size_limit() - current_committed_size;
79 size_t result_aligned = align_down(result, GenAlignment);
80 return result_aligned;
81 }
82
83 // Return the number of bytes the young gen is willing give up.
84 //
85 // Future implementations could check the survivors and if to_space is in the
86 // right place (below from_space), take a chunk from to_space.
87 size_t ASPSYoungGen::available_for_contraction() {
88 size_t uncommitted_bytes = virtual_space()->uncommitted_size();
89 if (uncommitted_bytes != 0) {
90 return uncommitted_bytes;
91 }
92
93 if (eden_space()->is_empty()) {
94 // Respect the minimum size for eden and for the young gen as a whole.
95 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
96 const size_t eden_alignment = SpaceAlignment;
97
98 assert(eden_space()->capacity_in_bytes() >= eden_alignment,
99 "Alignment is wrong");
100 size_t eden_avail = eden_space()->capacity_in_bytes() - eden_alignment;
101 eden_avail = align_down(eden_avail, GenAlignment);
102
103 assert(virtual_space()->committed_size() >= min_gen_size(),
104 "minimum gen size is wrong");
105 size_t gen_avail = virtual_space()->committed_size() - min_gen_size();
106 assert(virtual_space()->is_aligned(gen_avail), "not aligned");
107
108 const size_t max_contraction = MIN2(eden_avail, gen_avail);
109 // See comment for ASPSOldGen::available_for_contraction()
110 // for reasons the "increment" fraction is used.
111 PSAdaptiveSizePolicy* policy = heap->size_policy();
112 size_t result = policy->eden_increment_aligned_down(max_contraction);
113 size_t result_aligned = align_down(result, GenAlignment);
114
115 log_trace(gc, ergo)("ASPSYoungGen::available_for_contraction: " SIZE_FORMAT " K", result_aligned/K);
116 log_trace(gc, ergo)(" max_contraction " SIZE_FORMAT " K", max_contraction/K);
117 log_trace(gc, ergo)(" eden_avail " SIZE_FORMAT " K", eden_avail/K);
118 log_trace(gc, ergo)(" gen_avail " SIZE_FORMAT " K", gen_avail/K);
119
120 return result_aligned;
121 }
122
123 return 0;
124 }
125
126 // The current implementation only considers to the end of eden.
127 // If to_space is below from_space, to_space is not considered.
128 // to_space can be.
129 size_t ASPSYoungGen::available_to_live() {
130 const size_t alignment = SpaceAlignment;
131
132 // Include any space that is committed but is not in eden.
133 size_t available = pointer_delta(eden_space()->bottom(),
134 virtual_space()->low(),
135 sizeof(char));
136
137 const size_t eden_capacity = eden_space()->capacity_in_bytes();
138 if (eden_space()->is_empty() && eden_capacity > alignment) {
139 available += eden_capacity - alignment;
140 }
141 return available;
142 }
143
144 // Similar to PSYoungGen::resize_generation() but
145 // allows sum of eden_size and 2 * survivor_size to exceed _max_gen_size
146 // expands at the low end of the virtual space
147 // moves the boundary between the generations in order to expand
148 // some additional diagnostics
149 // If no additional changes are required, this can be deleted
150 // and the changes factored back into PSYoungGen::resize_generation().
151 bool ASPSYoungGen::resize_generation(size_t eden_size, size_t survivor_size) {
152 const size_t alignment = virtual_space()->alignment();
153 size_t orig_size = virtual_space()->committed_size();
154 bool size_changed = false;
155
156 // There used to be a guarantee here that
157 // (eden_size + 2*survivor_size) <= _max_gen_size
158 // This requirement is enforced by the calculation of desired_size
159 // below. It may not be true on entry since the size of the
160 // eden_size is no bounded by the generation size.
161
162 assert(max_size() == reserved().byte_size(), "max gen size problem?");
163 assert(min_gen_size() <= orig_size && orig_size <= max_size(),
164 "just checking");
165
166 // Adjust new generation size
167 const size_t eden_plus_survivors =
168 align_up(eden_size + 2 * survivor_size, alignment);
169 size_t desired_size = clamp(eden_plus_survivors, min_gen_size(), gen_size_limit());
170 assert(desired_size <= gen_size_limit(), "just checking");
171
172 if (desired_size > orig_size) {
173 // Grow the generation
174 size_t change = desired_size - orig_size;
175 HeapWord* prev_low = (HeapWord*) virtual_space()->low();
176 if (!virtual_space()->expand_by(change)) {
177 return false;
178 }
179 if (ZapUnusedHeapArea) {
180 // Mangle newly committed space immediately because it
181 // can be done here more simply that after the new
182 // spaces have been computed.
183 HeapWord* new_low = (HeapWord*) virtual_space()->low();
184 assert(new_low < prev_low, "Did not grow");
185
186 MemRegion mangle_region(new_low, prev_low);
187 SpaceMangler::mangle_region(mangle_region);
188 }
189 size_changed = true;
190 } else if (desired_size < orig_size) {
191 size_t desired_change = orig_size - desired_size;
192
193 // How much is available for shrinking.
194 size_t available_bytes = limit_gen_shrink(desired_change);
195 size_t change = MIN2(desired_change, available_bytes);
196 virtual_space()->shrink_by(change);
197 size_changed = true;
198 } else {
199 if (orig_size == gen_size_limit()) {
200 log_trace(gc)("ASPSYoung generation size at maximum: " SIZE_FORMAT "K", orig_size/K);
201 } else if (orig_size == min_gen_size()) {
202 log_trace(gc)("ASPSYoung generation size at minium: " SIZE_FORMAT "K", orig_size/K);
203 }
204 }
205
206 if (size_changed) {
207 reset_after_change();
208 log_trace(gc)("ASPSYoung generation size changed: " SIZE_FORMAT "K->" SIZE_FORMAT "K",
209 orig_size/K, virtual_space()->committed_size()/K);
210 }
211
212 guarantee(eden_plus_survivors <= virtual_space()->committed_size() ||
213 virtual_space()->committed_size() == max_size(), "Sanity");
214
215 return true;
216 }
217
218 // Similar to PSYoungGen::resize_spaces() but
219 // eden always starts at the low end of the committed virtual space
220 // current implementation does not allow holes between the spaces
221 // _young_generation_boundary has to be reset because it changes.
222 // so additional verification
223
224 void ASPSYoungGen::resize_spaces(size_t requested_eden_size,
225 size_t requested_survivor_size) {
226 assert(UseAdaptiveSizePolicy, "sanity check");
227 assert(requested_eden_size > 0 && requested_survivor_size > 0,
228 "just checking");
229
230 space_invariants();
231
232 // We require eden and to space to be empty
233 if ((!eden_space()->is_empty()) || (!to_space()->is_empty())) {
234 return;
235 }
236
237 log_trace(gc, ergo)("PSYoungGen::resize_spaces(requested_eden_size: "
238 SIZE_FORMAT
239 ", requested_survivor_size: " SIZE_FORMAT ")",
240 requested_eden_size, requested_survivor_size);
241 log_trace(gc, ergo)(" eden: [" PTR_FORMAT ".." PTR_FORMAT ") "
242 SIZE_FORMAT,
243 p2i(eden_space()->bottom()),
244 p2i(eden_space()->end()),
245 pointer_delta(eden_space()->end(), eden_space()->bottom(), sizeof(char)));
246 log_trace(gc, ergo)(" from: [" PTR_FORMAT ".." PTR_FORMAT ") "
247 SIZE_FORMAT,
248 p2i(from_space()->bottom()),
249 p2i(from_space()->end()),
250 pointer_delta(from_space()->end(), from_space()->bottom(), sizeof(char)));
251 log_trace(gc, ergo)(" to: [" PTR_FORMAT ".." PTR_FORMAT ") "
252 SIZE_FORMAT,
253 p2i(to_space()->bottom()),
254 p2i(to_space()->end()),
255 pointer_delta( to_space()->end(), to_space()->bottom(), sizeof(char)));
256
257 // There's nothing to do if the new sizes are the same as the current
258 if (requested_survivor_size == to_space()->capacity_in_bytes() &&
259 requested_survivor_size == from_space()->capacity_in_bytes() &&
260 requested_eden_size == eden_space()->capacity_in_bytes()) {
261 log_trace(gc, ergo)(" capacities are the right sizes, returning");
262 return;
263 }
264
265 char* eden_start = (char*)virtual_space()->low();
266 char* eden_end = (char*)eden_space()->end();
267 char* from_start = (char*)from_space()->bottom();
268 char* from_end = (char*)from_space()->end();
269 char* to_start = (char*)to_space()->bottom();
270 char* to_end = (char*)to_space()->end();
271
272 assert(eden_start < from_start, "Cannot push into from_space");
273
274 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
275 const bool maintain_minimum =
276 (requested_eden_size + 2 * requested_survivor_size) <= min_gen_size();
277
278 bool eden_from_to_order = from_start < to_start;
279 // Check whether from space is below to space
280 if (eden_from_to_order) {
281 // Eden, from, to
282
283 log_trace(gc, ergo)(" Eden, from, to:");
284
285 // Set eden
286 // "requested_eden_size" is a goal for the size of eden
287 // and may not be attainable. "eden_size" below is
288 // calculated based on the location of from-space and
289 // the goal for the size of eden. from-space is
290 // fixed in place because it contains live data.
291 // The calculation is done this way to avoid 32bit
292 // overflow (i.e., eden_start + requested_eden_size
293 // may too large for representation in 32bits).
294 size_t eden_size;
295 if (maintain_minimum) {
296 // Only make eden larger than the requested size if
297 // the minimum size of the generation has to be maintained.
298 // This could be done in general but policy at a higher
299 // level is determining a requested size for eden and that
300 // should be honored unless there is a fundamental reason.
301 eden_size = pointer_delta(from_start,
302 eden_start,
303 sizeof(char));
304 } else {
305 eden_size = MIN2(requested_eden_size,
306 pointer_delta(from_start, eden_start, sizeof(char)));
307 }
308
309 eden_end = eden_start + eden_size;
310 assert(eden_end >= eden_start, "addition overflowed");
311
312 // To may resize into from space as long as it is clear of live data.
313 // From space must remain page aligned, though, so we need to do some
314 // extra calculations.
315
316 // First calculate an optimal to-space
317 to_end = (char*)virtual_space()->high();
318 to_start = (char*)pointer_delta(to_end,
319 (char*)requested_survivor_size,
320 sizeof(char));
321
322 // Does the optimal to-space overlap from-space?
323 if (to_start < (char*)from_space()->end()) {
324 // Calculate the minimum offset possible for from_end
325 size_t from_size =
326 pointer_delta(from_space()->top(), from_start, sizeof(char));
327
328 // Should we be in this method if from_space is empty? Why not the set_space method? FIX ME!
329 if (from_size == 0) {
330 from_size = SpaceAlignment;
331 } else {
332 from_size = align_up(from_size, SpaceAlignment);
333 }
334
335 from_end = from_start + from_size;
336 assert(from_end > from_start, "addition overflow or from_size problem");
337
338 guarantee(from_end <= (char*)from_space()->end(),
339 "from_end moved to the right");
340
341 // Now update to_start with the new from_end
342 to_start = MAX2(from_end, to_start);
343 }
344
345 guarantee(to_start != to_end, "to space is zero sized");
346
347 log_trace(gc, ergo)(" [eden_start .. eden_end): "
348 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
349 p2i(eden_start),
350 p2i(eden_end),
351 pointer_delta(eden_end, eden_start, sizeof(char)));
352 log_trace(gc, ergo)(" [from_start .. from_end): "
353 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
354 p2i(from_start),
355 p2i(from_end),
356 pointer_delta(from_end, from_start, sizeof(char)));
357 log_trace(gc, ergo)(" [ to_start .. to_end): "
358 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
359 p2i(to_start),
360 p2i(to_end),
361 pointer_delta( to_end, to_start, sizeof(char)));
362 } else {
363 // Eden, to, from
364 log_trace(gc, ergo)(" Eden, to, from:");
365
366 // To space gets priority over eden resizing. Note that we position
367 // to space as if we were able to resize from space, even though from
368 // space is not modified.
369 // Giving eden priority was tried and gave poorer performance.
370 to_end = (char*)pointer_delta(virtual_space()->high(),
371 (char*)requested_survivor_size,
372 sizeof(char));
373 to_end = MIN2(to_end, from_start);
374 to_start = (char*)pointer_delta(to_end, (char*)requested_survivor_size,
375 sizeof(char));
376 // if the space sizes are to be increased by several times then
377 // 'to_start' will point beyond the young generation. In this case
378 // 'to_start' should be adjusted.
379 to_start = MAX2(to_start, eden_start + SpaceAlignment);
380
381 // Compute how big eden can be, then adjust end.
382 // See comments above on calculating eden_end.
383 size_t eden_size;
384 if (maintain_minimum) {
385 eden_size = pointer_delta(to_start, eden_start, sizeof(char));
386 } else {
387 eden_size = MIN2(requested_eden_size,
388 pointer_delta(to_start, eden_start, sizeof(char)));
389 }
390 eden_end = eden_start + eden_size;
391 assert(eden_end >= eden_start, "addition overflowed");
392
393 // Don't let eden shrink down to 0 or less.
394 eden_end = MAX2(eden_end, eden_start + SpaceAlignment);
395 to_start = MAX2(to_start, eden_end);
396
397 log_trace(gc, ergo)(" [eden_start .. eden_end): "
398 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
399 p2i(eden_start),
400 p2i(eden_end),
401 pointer_delta(eden_end, eden_start, sizeof(char)));
402 log_trace(gc, ergo)(" [ to_start .. to_end): "
403 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
404 p2i(to_start),
405 p2i(to_end),
406 pointer_delta( to_end, to_start, sizeof(char)));
407 log_trace(gc, ergo)(" [from_start .. from_end): "
408 "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
409 p2i(from_start),
410 p2i(from_end),
411 pointer_delta(from_end, from_start, sizeof(char)));
412 }
413
414
415 guarantee((HeapWord*)from_start <= from_space()->bottom(),
416 "from start moved to the right");
417 guarantee((HeapWord*)from_end >= from_space()->top(),
418 "from end moved into live data");
419 assert(is_object_aligned(eden_start), "checking alignment");
420 assert(is_object_aligned(from_start), "checking alignment");
421 assert(is_object_aligned(to_start), "checking alignment");
422
423 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)eden_end);
424 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
425 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)from_end);
426
427 // Let's make sure the call to initialize doesn't reset "top"!
428 DEBUG_ONLY(HeapWord* old_from_top = from_space()->top();)
429
430 // For logging block below
431 size_t old_from = from_space()->capacity_in_bytes();
432 size_t old_to = to_space()->capacity_in_bytes();
433
434 if (ZapUnusedHeapArea) {
435 // NUMA is a special case because a numa space is not mangled
436 // in order to not prematurely bind its address to memory to
437 // the wrong memory (i.e., don't want the GC thread to first
438 // touch the memory). The survivor spaces are not numa
439 // spaces and are mangled.
440 if (UseNUMA) {
441 if (eden_from_to_order) {
442 mangle_survivors(from_space(), fromMR, to_space(), toMR);
443 } else {
444 mangle_survivors(to_space(), toMR, from_space(), fromMR);
445 }
446 }
447
448 // If not mangling the spaces, do some checking to verify that
449 // the spaces are already mangled.
450 // The spaces should be correctly mangled at this point so
451 // do some checking here. Note that they are not being mangled
452 // in the calls to initialize().
453 // Must check mangling before the spaces are reshaped. Otherwise,
454 // the bottom or end of one space may have moved into an area
455 // covered by another space and a failure of the check may
456 // not correctly indicate which space is not properly mangled.
457
458 HeapWord* limit = (HeapWord*) virtual_space()->high();
459 eden_space()->check_mangled_unused_area(limit);
460 from_space()->check_mangled_unused_area(limit);
461 to_space()->check_mangled_unused_area(limit);
462 }
463 // When an existing space is being initialized, it is not
464 // mangled because the space has been previously mangled.
465 eden_space()->initialize(edenMR,
466 SpaceDecorator::Clear,
467 SpaceDecorator::DontMangle);
468 to_space()->initialize(toMR,
469 SpaceDecorator::Clear,
470 SpaceDecorator::DontMangle);
471 from_space()->initialize(fromMR,
472 SpaceDecorator::DontClear,
473 SpaceDecorator::DontMangle);
474
475 PSScavenge::set_young_generation_boundary(eden_space()->bottom());
476
477 assert(from_space()->top() == old_from_top, "from top changed!");
478
479 log_trace(gc, ergo)("AdaptiveSizePolicy::survivor space sizes: "
480 "collection: %d "
481 "(" SIZE_FORMAT ", " SIZE_FORMAT ") -> "
482 "(" SIZE_FORMAT ", " SIZE_FORMAT ") ",
483 ParallelScavengeHeap::heap()->total_collections(),
484 old_from, old_to,
485 from_space()->capacity_in_bytes(),
486 to_space()->capacity_in_bytes());
487
488 space_invariants();
489 }
490 void ASPSYoungGen::reset_after_change() {
491 assert_locked_or_safepoint(Heap_lock);
492
493 _reserved = MemRegion((HeapWord*)virtual_space()->low_boundary(),
494 (HeapWord*)virtual_space()->high_boundary());
495 PSScavenge::set_subject_to_discovery_span(_reserved);
496
497 HeapWord* new_eden_bottom = (HeapWord*)virtual_space()->low();
498 HeapWord* eden_bottom = eden_space()->bottom();
499 if (new_eden_bottom != eden_bottom) {
500 MemRegion eden_mr(new_eden_bottom, eden_space()->end());
501 eden_space()->initialize(eden_mr,
502 SpaceDecorator::Clear,
503 SpaceDecorator::Mangle);
504 PSScavenge::set_young_generation_boundary(eden_space()->bottom());
505 }
506 MemRegion cmr((HeapWord*)virtual_space()->low(),
507 (HeapWord*)virtual_space()->high());
508 ParallelScavengeHeap::heap()->barrier_set()->card_table()->resize_covered_region(cmr);
509
510 space_invariants();
511 }