1 /* 2 * Copyright (c) 2019, 2023, 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 = { nullptr, 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. 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() - (intptr_t)os::vm_page_size()) || 83 base() == nullptr, "invalid value"); 84 assert(shift() == LogMinObjAlignmentInBytes || 85 shift() == 0, "invalid value"); 86 #endif 87 } 88 89 void CompressedOops::set_base(address base) { 90 assert(UseCompressedOops, "no compressed oops?"); 91 _narrow_oop._base = base; 92 } 93 94 void CompressedOops::set_shift(int shift) { 95 _narrow_oop._shift = shift; 96 } 97 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 } 102 103 bool CompressedOops::is_in(void* addr) { 104 return _heap_address_range.contains(addr); 105 } 106 107 bool CompressedOops::is_in(MemRegion mr) { 108 return _heap_address_range.contains(mr); 109 } 110 111 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 } 126 127 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. 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. 150 bool CompressedOops::base_disjoint() { 151 return _narrow_oop._base != nullptr && 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. 157 bool CompressedOops::base_overlaps() { 158 return _narrow_oop._base != nullptr && !is_disjoint_heap_base_address(_narrow_oop._base); 159 } 160 161 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 = { nullptr, 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). 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 - a lot. 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). 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 } 282 283 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_X, p2i(base()), shift(), 286 range()); 287 } 288 289 void CompressedKlassPointers::set_base(address base) { 290 assert(UseCompressedClassPointers, "no compressed klass ptrs?"); 291 _narrow_klass._base = base; 292 } 293 294 void CompressedKlassPointers::set_shift(int shift) { 295 assert(shift == 0 || shift == LogKlassAlignmentInBytes, "invalid shift for klass ptrs"); 296 _narrow_klass._shift = shift; 297 } 298 299 void CompressedKlassPointers::set_range(size_t range) { 300 assert(UseCompressedClassPointers, "no compressed klass ptrs?"); 301 _range = range; 302 }