1 /*
2 * Copyright (c) 2019, 2021, 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 "logging/log.hpp"
27 #include "logging/logStream.hpp"
28 #include "memory/memRegion.hpp"
29 #include "memory/resourceArea.hpp"
30 #include "memory/universe.hpp"
31 #include "memory/virtualspace.hpp"
32 #include "oops/compressedOops.hpp"
33 #include "gc/shared/collectedHeap.hpp"
34 #include "runtime/arguments.hpp"
35 #include "runtime/globals.hpp"
36
37 // For UseCompressedOops.
38 NarrowPtrStruct CompressedOops::_narrow_oop = { NULL, 0, true };
39 MemRegion CompressedOops::_heap_address_range;
40
41 // Choose the heap base address and oop encoding mode
42 // when compressed oops are used:
43 // Unscaled - Use 32-bits oops without encoding when
44 // NarrowOopHeapBaseMin + heap_size < 4Gb
45 // ZeroBased - Use zero based compressed oops with encoding when
46 // NarrowOopHeapBaseMin + heap_size < 32Gb
47 // HeapBased - Use compressed oops with heap base + encoding.
initialize(const ReservedHeapSpace & heap_space)48 void CompressedOops::initialize(const ReservedHeapSpace& heap_space) {
49 #ifdef _LP64
50 // Subtract a page because something can get allocated at heap base.
51 // This also makes implicit null checking work, because the
52 // memory+1 page below heap_base needs to cause a signal.
53 // See needs_explicit_null_check.
54 // Only set the heap base for compressed oops because it indicates
55 // compressed oops for pstack code.
56 if ((uint64_t)heap_space.end() > UnscaledOopHeapMax) {
57 // Didn't reserve heap below 4Gb. Must shift.
58 set_shift(LogMinObjAlignmentInBytes);
59 }
60 if ((uint64_t)heap_space.end() <= OopEncodingHeapMax) {
61 // Did reserve heap below 32Gb. Can use base == 0;
62 set_base(0);
63 } else {
64 set_base((address)heap_space.compressed_oop_base());
65 }
66
67 _heap_address_range = heap_space.region();
68
69 LogTarget(Debug, gc, heap, coops) lt;
70 if (lt.is_enabled()) {
71 ResourceMark rm;
72 LogStream ls(lt);
73 print_mode(&ls);
74 }
75
76 // Tell tests in which mode we run.
77 Arguments::PropertyList_add(new SystemProperty("java.vm.compressedOopsMode",
78 mode_to_string(mode()),
79 false));
80
81 // base() is one page below the heap.
82 assert((intptr_t)base() <= ((intptr_t)_heap_address_range.start() - os::vm_page_size()) ||
83 base() == NULL, "invalid value");
84 assert(shift() == LogMinObjAlignmentInBytes ||
85 shift() == 0, "invalid value");
86 #endif
87 }
88
set_base(address base)89 void CompressedOops::set_base(address base) {
90 assert(UseCompressedOops, "no compressed oops?");
91 _narrow_oop._base = base;
92 }
93
set_shift(int shift)94 void CompressedOops::set_shift(int shift) {
95 _narrow_oop._shift = shift;
96 }
97
set_use_implicit_null_checks(bool use)98 void CompressedOops::set_use_implicit_null_checks(bool use) {
99 assert(UseCompressedOops, "no compressed ptrs?");
100 _narrow_oop._use_implicit_null_checks = use;
101 }
102
is_in(void * addr)103 bool CompressedOops::is_in(void* addr) {
104 return _heap_address_range.contains(addr);
105 }
106
is_in(MemRegion mr)107 bool CompressedOops::is_in(MemRegion mr) {
108 return _heap_address_range.contains(mr);
109 }
110
mode()111 CompressedOops::Mode CompressedOops::mode() {
112 if (base_disjoint()) {
113 return DisjointBaseNarrowOop;
114 }
115
116 if (base() != 0) {
117 return HeapBasedNarrowOop;
118 }
119
120 if (shift() != 0) {
121 return ZeroBasedNarrowOop;
122 }
123
124 return UnscaledNarrowOop;
125 }
126
mode_to_string(Mode mode)127 const char* CompressedOops::mode_to_string(Mode mode) {
128 switch (mode) {
129 case UnscaledNarrowOop:
130 return "32-bit";
131 case ZeroBasedNarrowOop:
132 return "Zero based";
133 case DisjointBaseNarrowOop:
134 return "Non-zero disjoint base";
135 case HeapBasedNarrowOop:
136 return "Non-zero based";
137 default:
138 ShouldNotReachHere();
139 return "";
140 }
141 }
142
143 // Test whether bits of addr and possible offsets into the heap overlap.
is_disjoint_heap_base_address(address addr)144 bool CompressedOops::is_disjoint_heap_base_address(address addr) {
145 return (((uint64_t)(intptr_t)addr) &
146 (((uint64_t)UCONST64(0xFFFFffffFFFFffff)) >> (32-LogMinObjAlignmentInBytes))) == 0;
147 }
148
149 // Check for disjoint base compressed oops.
base_disjoint()150 bool CompressedOops::base_disjoint() {
151 return _narrow_oop._base != NULL && is_disjoint_heap_base_address(_narrow_oop._base);
152 }
153
154 // Check for real heapbased compressed oops.
155 // We must subtract the base as the bits overlap.
156 // If we negate above function, we also get unscaled and zerobased.
base_overlaps()157 bool CompressedOops::base_overlaps() {
158 return _narrow_oop._base != NULL && !is_disjoint_heap_base_address(_narrow_oop._base);
159 }
160
print_mode(outputStream * st)161 void CompressedOops::print_mode(outputStream* st) {
162 st->print("Heap address: " PTR_FORMAT ", size: " SIZE_FORMAT " MB",
163 p2i(_heap_address_range.start()), _heap_address_range.byte_size()/M);
164
165 st->print(", Compressed Oops mode: %s", mode_to_string(mode()));
166
167 if (base() != 0) {
168 st->print(": " PTR_FORMAT, p2i(base()));
169 }
170
171 if (shift() != 0) {
172 st->print(", Oop shift amount: %d", shift());
173 }
174
175 if (!use_implicit_null_checks()) {
176 st->print(", no protected page in front of the heap");
177 }
178 st->cr();
179 }
180
181 // For UseCompressedClassPointers.
182 NarrowPtrStruct CompressedKlassPointers::_narrow_klass = { NULL, 0, true };
183
184 // CompressedClassSpaceSize set to 1GB, but appear 3GB away from _narrow_ptrs_base during CDS dump.
185 // (Todo: we should #ifdef out CompressedKlassPointers for 32bit completely and fix all call sites which
186 // are compiled for 32bit to LP64_ONLY).
187 size_t CompressedKlassPointers::_range = 0;
188
189
190 // Given an address range [addr, addr+len) which the encoding is supposed to
191 // cover, choose base, shift and range.
192 // The address range is the expected range of uncompressed Klass pointers we
193 // will encounter (and the implicit promise that there will be no Klass
194 // structures outside this range).
initialize(address addr,size_t len)195 void CompressedKlassPointers::initialize(address addr, size_t len) {
196 #ifdef _LP64
197 assert(is_valid_base(addr), "Address must be a valid encoding base");
198 address const end = addr + len;
199
200 address base;
201 int shift;
202 size_t range;
203
204 if (UseSharedSpaces || DumpSharedSpaces) {
205
206 // Special requirements if CDS is active:
207 // Encoding base and shift must be the same between dump and run time.
208 // CDS takes care that the SharedBaseAddress and CompressedClassSpaceSize
209 // are the same. Archive size will be probably different at runtime, but
210 // it can only be smaller than at, never larger, since archives get
211 // shrunk at the end of the dump process.
212 // From that it follows that the range [addr, len) we are handed in at
213 // runtime will start at the same address then at dumptime, and its len
214 // may be smaller at runtime then it was at dump time.
215 //
216 // To be very careful here, we avoid any optimizations and just keep using
217 // the same address and shift value. Specifically we avoid using zero-based
218 // encoding. We also set the expected value range to 4G (encoding range
219 // cannot be larger than that).
220
221 base = addr;
222
223 // JDK-8265705
224 // This is a temporary fix for aarch64: there, if the range-to-be-encoded is located
225 // below 32g, either encoding base should be zero or base should be aligned to 4G
226 // and shift should be zero. The simplest way to fix this for now is to force
227 // shift to zero for both runtime and dumptime.
228 // Note however that this is not a perfect solution. Ideally this whole function
229 // should be CDS agnostic, that would simplify it - and testing - alot. See JDK-8267141
230 // for details.
231 shift = 0;
232
233 // This must be true since at dumptime cds+ccs is 4G, at runtime it can
234 // only be smaller, see comment above.
235 assert(len <= 4 * G, "Encoding range cannot be larger than 4G");
236 range = 4 * G;
237
238 } else {
239
240 // Otherwise we attempt to use a zero base if the range fits in lower 32G.
241 if (end <= (address)KlassEncodingMetaspaceMax) {
242 base = 0;
243 } else {
244 base = addr;
245 }
246
247 // Highest offset a Klass* can ever have in relation to base.
248 range = end - base;
249
250 // We may not even need a shift if the range fits into 32bit:
251 const uint64_t UnscaledClassSpaceMax = (uint64_t(max_juint) + 1);
252 if (range < UnscaledClassSpaceMax) {
253 shift = 0;
254 } else {
255 shift = LogKlassAlignmentInBytes;
256 }
257
258 }
259
260 set_base(base);
261 set_shift(shift);
262 set_range(range);
263 #else
264 fatal("64bit only.");
265 #endif
266 }
267
268 // Given an address p, return true if p can be used as an encoding base.
269 // (Some platforms have restrictions of what constitutes a valid base address).
is_valid_base(address p)270 bool CompressedKlassPointers::is_valid_base(address p) {
271 #ifdef AARCH64
272 // Below 32G, base must be aligned to 4G.
273 // Above that point, base must be aligned to 32G
274 if (p < (address)(32 * G)) {
275 return is_aligned(p, 4 * G);
276 }
277 return is_aligned(p, (4 << LogKlassAlignmentInBytes) * G);
278 #else
279 return true;
280 #endif
281 }
282
print_mode(outputStream * st)283 void CompressedKlassPointers::print_mode(outputStream* st) {
284 st->print_cr("Narrow klass base: " PTR_FORMAT ", Narrow klass shift: %d, "
285 "Narrow klass range: " SIZE_FORMAT_HEX, p2i(base()), shift(),
286 range());
287 }
288
set_base(address base)289 void CompressedKlassPointers::set_base(address base) {
290 assert(UseCompressedClassPointers, "no compressed klass ptrs?");
291 _narrow_klass._base = base;
292 }
293
set_shift(int shift)294 void CompressedKlassPointers::set_shift(int shift) {
295 assert(shift == 0 || shift == LogKlassAlignmentInBytes, "invalid shift for klass ptrs");
296 _narrow_klass._shift = shift;
297 }
298
set_range(size_t range)299 void CompressedKlassPointers::set_range(size_t range) {
300 assert(UseCompressedClassPointers, "no compressed klass ptrs?");
301 _range = range;
302 }
303