1 /*
2 * Copyright (c) 2015, 2018, 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 #include "precompiled.hpp"
25 #include "gc/z/zAddress.inline.hpp"
26 #include "gc/z/zBackingFile_linux_x86.hpp"
27 #include "gc/z/zErrno.hpp"
28 #include "gc/z/zLargePages.inline.hpp"
29 #include "gc/z/zMemory.hpp"
30 #include "gc/z/zNUMA.hpp"
31 #include "gc/z/zPhysicalMemory.inline.hpp"
32 #include "gc/z/zPhysicalMemoryBacking_linux_x86.hpp"
33 #include "logging/log.hpp"
34 #include "runtime/os.hpp"
35 #include "utilities/align.hpp"
36 #include "utilities/debug.hpp"
37
38 #include <stdio.h>
39 #include <sys/mman.h>
40 #include <sys/types.h>
41
42 // Support for building on older Linux systems
43 #ifndef MADV_HUGEPAGE
44 #define MADV_HUGEPAGE 14
45 #endif
46
47 // Proc file entry for max map mount
48 #define ZFILENAME_PROC_MAX_MAP_COUNT "/proc/sys/vm/max_map_count"
49
50 ZPhysicalMemoryBacking::ZPhysicalMemoryBacking(size_t max_capacity, size_t granule_size) :
51 _manager(),
52 _file(),
53 _granule_size(granule_size) {
54
55 if (!_file.is_initialized()) {
56 return;
57 }
58
59 // Check and warn if max map count is too low
60 check_max_map_count(max_capacity, granule_size);
61
62 // Check and warn if available space on filesystem is too low
63 check_available_space_on_filesystem(max_capacity);
64 }
65
66 void ZPhysicalMemoryBacking::check_max_map_count(size_t max_capacity, size_t granule_size) const {
67 const char* const filename = ZFILENAME_PROC_MAX_MAP_COUNT;
68 FILE* const file = fopen(filename, "r");
69 if (file == NULL) {
70 // Failed to open file, skip check
71 log_debug(gc, init)("Failed to open %s", filename);
72 return;
73 }
74
75 size_t actual_max_map_count = 0;
76 const int result = fscanf(file, SIZE_FORMAT, &actual_max_map_count);
77 fclose(file);
78 if (result != 1) {
79 // Failed to read file, skip check
80 log_debug(gc, init)("Failed to read %s", filename);
81 return;
82 }
83
84 // The required max map count is impossible to calculate exactly since subsystems
85 // other than ZGC are also creating memory mappings, and we have no control over that.
86 // However, ZGC tends to create the most mappings and dominate the total count.
87 // In the worst cases, ZGC will map each granule three times, i.e. once per heap view.
88 // We speculate that we need another 20% to allow for non-ZGC subsystems to map memory.
89 const size_t required_max_map_count = (max_capacity / granule_size) * 3 * 1.2;
90 if (actual_max_map_count < required_max_map_count) {
91 log_warning(gc, init)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
92 log_warning(gc, init)("The system limit on number of memory mappings per process might be too low "
93 "for the given");
94 log_warning(gc, init)("max Java heap size (" SIZE_FORMAT "M). Please adjust %s to allow for at",
95 max_capacity / M, filename);
96 log_warning(gc, init)("least " SIZE_FORMAT " mappings (current limit is " SIZE_FORMAT "). Continuing "
97 "execution with the current", required_max_map_count, actual_max_map_count);
98 log_warning(gc, init)("limit could lead to a fatal error, due to failure to map memory.");
99 }
100 }
101
102 void ZPhysicalMemoryBacking::check_available_space_on_filesystem(size_t max_capacity) const {
103 // Note that the available space on a tmpfs or a hugetlbfs filesystem
104 // will be zero if no size limit was specified when it was mounted.
105 const size_t available = _file.available();
106 if (available == 0) {
107 // No size limit set, skip check
108 log_info(gc, init)("Available space on backing filesystem: N/A");
109 return;
110 }
111
112 log_info(gc, init)("Available space on backing filesystem: " SIZE_FORMAT "M",
113 available / M);
114
115 // Warn if the filesystem doesn't currently have enough space available to hold
116 // the max heap size. The max heap size will be capped if we later hit this limit
117 // when trying to expand the heap.
118 if (available < max_capacity) {
119 log_warning(gc, init)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
120 log_warning(gc, init)("Not enough space available on the backing filesystem to hold the current "
121 "max Java heap");
122 log_warning(gc, init)("size (" SIZE_FORMAT "M). Please adjust the size of the backing filesystem "
123 "accordingly (available", max_capacity / M);
124 log_warning(gc, init)("space is currently " SIZE_FORMAT "M). Continuing execution with the current "
125 "filesystem size could", available / M);
126 log_warning(gc, init)("lead to a premature OutOfMemoryError being thrown, due to failure to map "
127 "memory.");
128 }
129 }
130
131 bool ZPhysicalMemoryBacking::is_initialized() const {
132 return _file.is_initialized();
133 }
134
135 size_t ZPhysicalMemoryBacking::try_expand(size_t old_capacity, size_t new_capacity) {
136 assert(old_capacity < new_capacity, "Invalid old/new capacity");
137
138 const size_t capacity = _file.try_expand(old_capacity, new_capacity - old_capacity, _granule_size);
139 if (capacity > old_capacity) {
140 // Add expanded capacity to free list
141 _manager.free(old_capacity, capacity - old_capacity);
142 }
143
144 return capacity;
145 }
146
147 ZPhysicalMemory ZPhysicalMemoryBacking::alloc(size_t size) {
148 assert(is_aligned(size, _granule_size), "Invalid size");
149
150 ZPhysicalMemory pmem;
151
152 // Allocate segments
153 for (size_t allocated = 0; allocated < size; allocated += _granule_size) {
154 const uintptr_t start = _manager.alloc_from_front(_granule_size);
155 assert(start != UINTPTR_MAX, "Allocation should never fail");
156 pmem.add_segment(ZPhysicalMemorySegment(start, _granule_size));
157 }
158
159 return pmem;
160 }
161
162 void ZPhysicalMemoryBacking::free(ZPhysicalMemory pmem) {
163 const size_t nsegments = pmem.nsegments();
164
165 // Free segments
166 for (size_t i = 0; i < nsegments; i++) {
167 const ZPhysicalMemorySegment segment = pmem.segment(i);
168 _manager.free(segment.start(), segment.size());
169 }
170 }
171
172 void ZPhysicalMemoryBacking::map_failed(ZErrno err) const {
173 if (err == ENOMEM) {
174 fatal("Failed to map memory. Please check the system limit on number of "
175 "memory mappings allowed per process (see %s)", ZFILENAME_PROC_MAX_MAP_COUNT);
176 } else {
177 fatal("Failed to map memory (%s)", err.to_string());
178 }
179 }
180
181 void ZPhysicalMemoryBacking::advise_view(uintptr_t addr, size_t size) const {
182 if (madvise((void*)addr, size, MADV_HUGEPAGE) == -1) {
183 ZErrno err;
184 log_error(gc)("Failed to advise use of transparent huge pages (%s)", err.to_string());
185 }
186 }
187
188 void ZPhysicalMemoryBacking::pretouch_view(uintptr_t addr, size_t size) const {
189 const size_t page_size = ZLargePages::is_explicit() ? os::large_page_size() : os::vm_page_size();
190 os::pretouch_memory((void*)addr, (void*)(addr + size), page_size);
191 }
192
193 void ZPhysicalMemoryBacking::map_view(ZPhysicalMemory pmem, uintptr_t addr, bool pretouch) const {
194 const size_t nsegments = pmem.nsegments();
195
196 // Map segments
197 for (size_t i = 0; i < nsegments; i++) {
198 const ZPhysicalMemorySegment segment = pmem.segment(i);
199 const size_t size = segment.size();
200 const void* const res = mmap((void*)addr, size, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, _file.fd(), segment.start());
201 if (res == MAP_FAILED) {
202 ZErrno err;
203 map_failed(err);
204 }
205
206 // Advise on use of transparent huge pages before touching it
207 if (ZLargePages::is_transparent()) {
208 advise_view(addr, size);
209 }
210
211 // NUMA interleave memory before touching it
212 ZNUMA::memory_interleave(addr, size);
213
214 if (pretouch) {
215 pretouch_view(addr, size);
216 }
217
218 addr += size;
219 }
220 }
221
222 void ZPhysicalMemoryBacking::unmap_view(ZPhysicalMemory pmem, uintptr_t addr) const {
223 // Note that we must keep the address space reservation intact and just detach
224 // the backing memory. For this reason we map a new anonymous, non-accessible
225 // and non-reserved page over the mapping instead of actually unmapping.
226 const size_t size = pmem.size();
227 const void* const res = mmap((void*)addr, size, PROT_NONE, MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
228 if (res == MAP_FAILED) {
229 ZErrno err;
230 map_failed(err);
231 }
232 }
233
234 uintptr_t ZPhysicalMemoryBacking::nmt_address(uintptr_t offset) const {
235 // From an NMT point of view we treat the first heap mapping (marked0) as committed
236 return ZAddress::marked0(offset);
237 }
238
239 void ZPhysicalMemoryBacking::map(ZPhysicalMemory pmem, uintptr_t offset) const {
240 if (ZUnmapBadViews) {
241 // Only map the good view, for debugging only
242 map_view(pmem, ZAddress::good(offset), AlwaysPreTouch);
243 } else {
244 // Map all views
245 map_view(pmem, ZAddress::marked0(offset), AlwaysPreTouch);
246 map_view(pmem, ZAddress::marked1(offset), AlwaysPreTouch);
247 map_view(pmem, ZAddress::remapped(offset), AlwaysPreTouch);
248 }
249 }
250
251 void ZPhysicalMemoryBacking::unmap(ZPhysicalMemory pmem, uintptr_t offset) const {
252 if (ZUnmapBadViews) {
253 // Only map the good view, for debugging only
254 unmap_view(pmem, ZAddress::good(offset));
255 } else {
256 // Unmap all views
257 unmap_view(pmem, ZAddress::marked0(offset));
258 unmap_view(pmem, ZAddress::marked1(offset));
259 unmap_view(pmem, ZAddress::remapped(offset));
260 }
261 }
262
263 void ZPhysicalMemoryBacking::flip(ZPhysicalMemory pmem, uintptr_t offset) const {
264 assert(ZUnmapBadViews, "Should be enabled");
265 const uintptr_t addr_good = ZAddress::good(offset);
266 const uintptr_t addr_bad = ZAddress::is_marked(ZAddressGoodMask) ? ZAddress::remapped(offset) : ZAddress::marked(offset);
267 // Map/Unmap views
268 map_view(pmem, addr_good, false /* pretouch */);
269 unmap_view(pmem, addr_bad);
270 }