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