Thu, 21 Aug 2014 16:44:41 +0200
8055098: WB API should be extended to provide information about size and age of object.
Summary: Extend the WhiteBox API to provide information about the size and age of objects. Further add a mechanism to trigger a young GC.
Reviewed-by: tschatzl, sjohanss
Contributed-by: Leonid Mesnik <leonid.mesnik@oracle.com>
1 /*
2 * Copyright (c) 2011, 2014, 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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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
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
28 #include "runtime/orderAccess.inline.hpp"
30 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
31 HeapRegion* G1AllocRegion::_dummy_region = NULL;
33 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
34 assert(_dummy_region == NULL, "should be set once");
35 assert(dummy_region != NULL, "pre-condition");
36 assert(dummy_region->free() == 0, "pre-condition");
38 // Make sure that any allocation attempt on this region will fail
39 // and will not trigger any asserts.
40 assert(allocate(dummy_region, 1, false) == NULL, "should fail");
41 assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
42 assert(allocate(dummy_region, 1, true) == NULL, "should fail");
43 assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
45 _g1h = g1h;
46 _dummy_region = dummy_region;
47 }
49 void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
50 bool bot_updates) {
51 assert(alloc_region != NULL && alloc_region != _dummy_region,
52 "pre-condition");
54 // Other threads might still be trying to allocate using a CAS out
55 // of the region we are trying to retire, as they can do so without
56 // holding the lock. So, we first have to make sure that noone else
57 // can allocate out of it by doing a maximal allocation. Even if our
58 // CAS attempt fails a few times, we'll succeed sooner or later
59 // given that failed CAS attempts mean that the region is getting
60 // closed to being full.
61 size_t free_word_size = alloc_region->free() / HeapWordSize;
63 // This is the minimum free chunk we can turn into a dummy
64 // object. If the free space falls below this, then noone can
65 // allocate in this region anyway (all allocation requests will be
66 // of a size larger than this) so we won't have to perform the dummy
67 // allocation.
68 size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
70 while (free_word_size >= min_word_size_to_fill) {
71 HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
72 if (dummy != NULL) {
73 // If the allocation was successful we should fill in the space.
74 CollectedHeap::fill_with_object(dummy, free_word_size);
75 alloc_region->set_pre_dummy_top(dummy);
76 break;
77 }
79 free_word_size = alloc_region->free() / HeapWordSize;
80 // It's also possible that someone else beats us to the
81 // allocation and they fill up the region. In that case, we can
82 // just get out of the loop.
83 }
84 assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
85 "post-condition");
86 }
88 void G1AllocRegion::retire(bool fill_up) {
89 assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
91 trace("retiring");
92 HeapRegion* alloc_region = _alloc_region;
93 if (alloc_region != _dummy_region) {
94 // We never have to check whether the active region is empty or not,
95 // and potentially free it if it is, given that it's guaranteed that
96 // it will never be empty.
97 assert(!alloc_region->is_empty(),
98 ar_ext_msg(this, "the alloc region should never be empty"));
100 if (fill_up) {
101 fill_up_remaining_space(alloc_region, _bot_updates);
102 }
104 assert(alloc_region->used() >= _used_bytes_before,
105 ar_ext_msg(this, "invariant"));
106 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
107 retire_region(alloc_region, allocated_bytes);
108 _used_bytes_before = 0;
109 _alloc_region = _dummy_region;
110 }
111 trace("retired");
112 }
114 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
115 bool force) {
116 assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));
117 assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));
119 trace("attempting region allocation");
120 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
121 if (new_alloc_region != NULL) {
122 new_alloc_region->reset_pre_dummy_top();
123 // Need to do this before the allocation
124 _used_bytes_before = new_alloc_region->used();
125 HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
126 assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));
128 OrderAccess::storestore();
129 // Note that we first perform the allocation and then we store the
130 // region in _alloc_region. This is the reason why an active region
131 // can never be empty.
132 _alloc_region = new_alloc_region;
133 _count += 1;
134 trace("region allocation successful");
135 return result;
136 } else {
137 trace("region allocation failed");
138 return NULL;
139 }
140 ShouldNotReachHere();
141 }
143 void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {
144 msg->append("[%s] %s c: %u b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT,
145 _name, message, _count, BOOL_TO_STR(_bot_updates),
146 p2i(_alloc_region), _used_bytes_before);
147 }
149 void G1AllocRegion::init() {
150 trace("initializing");
151 assert(_alloc_region == NULL && _used_bytes_before == 0,
152 ar_ext_msg(this, "pre-condition"));
153 assert(_dummy_region != NULL, ar_ext_msg(this, "should have been set"));
154 _alloc_region = _dummy_region;
155 _count = 0;
156 trace("initialized");
157 }
159 void G1AllocRegion::set(HeapRegion* alloc_region) {
160 trace("setting");
161 // We explicitly check that the region is not empty to make sure we
162 // maintain the "the alloc region cannot be empty" invariant.
163 assert(alloc_region != NULL && !alloc_region->is_empty(),
164 ar_ext_msg(this, "pre-condition"));
165 assert(_alloc_region == _dummy_region &&
166 _used_bytes_before == 0 && _count == 0,
167 ar_ext_msg(this, "pre-condition"));
169 _used_bytes_before = alloc_region->used();
170 _alloc_region = alloc_region;
171 _count += 1;
172 trace("set");
173 }
175 HeapRegion* G1AllocRegion::release() {
176 trace("releasing");
177 HeapRegion* alloc_region = _alloc_region;
178 retire(false /* fill_up */);
179 assert(_alloc_region == _dummy_region,
180 ar_ext_msg(this, "post-condition of retire()"));
181 _alloc_region = NULL;
182 trace("released");
183 return (alloc_region == _dummy_region) ? NULL : alloc_region;
184 }
186 #if G1_ALLOC_REGION_TRACING
187 void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {
188 // All the calls to trace that set either just the size or the size
189 // and the result are considered part of level 2 tracing and are
190 // skipped during level 1 tracing.
191 if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
192 const size_t buffer_length = 128;
193 char hr_buffer[buffer_length];
194 char rest_buffer[buffer_length];
196 HeapRegion* alloc_region = _alloc_region;
197 if (alloc_region == NULL) {
198 jio_snprintf(hr_buffer, buffer_length, "NULL");
199 } else if (alloc_region == _dummy_region) {
200 jio_snprintf(hr_buffer, buffer_length, "DUMMY");
201 } else {
202 jio_snprintf(hr_buffer, buffer_length,
203 HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
204 }
206 if (G1_ALLOC_REGION_TRACING > 1) {
207 if (result != NULL) {
208 jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT,
209 word_size, result);
210 } else if (word_size != 0) {
211 jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);
212 } else {
213 jio_snprintf(rest_buffer, buffer_length, "");
214 }
215 } else {
216 jio_snprintf(rest_buffer, buffer_length, "");
217 }
219 tty->print_cr("[%s] %u %s : %s %s",
220 _name, _count, hr_buffer, str, rest_buffer);
221 }
222 }
223 #endif // G1_ALLOC_REGION_TRACING
225 G1AllocRegion::G1AllocRegion(const char* name,
226 bool bot_updates)
227 : _name(name), _bot_updates(bot_updates),
228 _alloc_region(NULL), _count(0), _used_bytes_before(0) { }