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1 // Copyright (c) 2015 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #include "base/memory/persistent_memory_allocator.h" | |
6 | |
7 #include <assert.h> | |
8 #include <algorithm> | |
9 | |
10 #include "base/logging.h" | |
11 #include "base/metrics/histogram_macros.h" | |
12 | |
13 namespace { | |
14 | |
15 // Required range of memory segment sizes. It has to fit in an unsigned 32-bit | |
16 // number and should be a power of 2 in order to accomodate almost any page | |
17 // size. | |
18 const uint32_t kSegmentMinSize = 1 << 10; // 1 KiB | |
19 const uint32_t kSegmentMaxSize = 1 << 30; // 1 GiB | |
20 | |
21 // All allocations and data-structures must be aligned to this byte boundary. | |
22 // Alignment as large as the physical bus between CPU and RAM is _required_ | |
23 // for some architectures, is simply more efficient on other CPUs, and | |
24 // generally a Good Idea(tm) for all platforms as it reduces/eliminates the | |
25 // chance that a type will span cache lines. Alignment mustn't be less | |
26 // than 8 to ensure proper alignment for all types. The rest is a balance | |
27 // between reducing spans across multiple cache lines and wasted space spent | |
28 // padding out allocations. An alignment of 16 would ensure that the block | |
29 // header structure always sits in a single cache line. An average of about | |
30 // 1/2 this value will be wasted with every allocation. | |
31 const uint32_t kAllocAlignment = 8; | |
32 | |
33 // A constant (random) value placed in the shared metadata to identify | |
34 // an already initialized memory segment. | |
35 const uint32_t kGlobalCookie = 0x408305DC; | |
36 | |
37 // The current version of the metadata. If updates are made that change | |
38 // the metadata, the version number can be queried to operate in a backward- | |
39 // compatible manner until the memory segment is completely re-initalized. | |
40 const uint32_t kGlobalVersion = 1; | |
41 | |
42 // Constant values placed in the block headers to indicate its state. | |
43 const uint32_t kBlockCookieFree = 0; | |
44 const uint32_t kBlockCookieQueue = 1; | |
45 const uint32_t kBlockCookieWasted = (uint32_t)-1; | |
46 const uint32_t kBlockCookieAllocated = 0xC8799269; | |
47 | |
48 // TODO(bcwhite): When acceptable, consider moving flags to std::atomic<char> | |
49 // types rather than combined bitfield. | |
50 | |
51 // Flags stored in the flags_ field of the SharedMetaData structure below. | |
52 enum : int { | |
53 kFlagCorrupt = 1 << 0, | |
54 kFlagFull = 1 << 1 | |
55 }; | |
56 | |
57 bool CheckFlag(volatile std::atomic<uint32_t>* flags, int flag) { | |
58 uint32_t loaded_flags = flags->load(); | |
59 return (loaded_flags & flag) != 0; | |
60 } | |
61 | |
62 void SetFlag(volatile std::atomic<uint32_t>* flags, int flag) { | |
63 uint32_t loaded_flags = flags->load(); | |
64 for (;;) { | |
65 uint32_t new_flags = (loaded_flags & ~flag) | flag; | |
66 // In the failue case, actual "flags" value stored in loaded_flags. | |
67 if (flags->compare_exchange_weak(loaded_flags, new_flags)) | |
68 break; | |
69 } | |
70 } | |
71 | |
72 } // namespace | |
73 | |
74 namespace base { | |
75 | |
76 // The block-header is placed at the top of every allocation within the | |
77 // segment to describe the data that follows it. | |
78 struct PersistentMemoryAllocator::BlockHeader { | |
79 uint32_t size; // Number of bytes in this block, including header. | |
80 uint32_t cookie; // Constant value indicating completed allocation. | |
81 uint32_t type_id; // A number provided by caller indicating data type. | |
82 std::atomic<uint32_t> next; // Pointer to the next block when iterating. | |
83 }; | |
84 | |
85 // The shared metadata exists once at the top of the memory segment to | |
86 // describe the state of the allocator to all processes. | |
87 struct PersistentMemoryAllocator::SharedMetadata { | |
88 uint32_t cookie; // Some value that indicates complete initialization. | |
89 uint32_t size; // Total size of memory segment. | |
90 uint32_t page_size; // Paging size within memory segment. | |
91 uint32_t version; // Version code so upgrades don't break. | |
92 std::atomic<uint32_t> freeptr; // Offset/ref to first free space in segment. | |
93 std::atomic<uint32_t> flags; // Bitfield of information flags. | |
94 uint32_t name; // Reference to stored name string. | |
95 | |
96 // The "iterable" queue is an M&S Queue as described here, append-only: | |
97 // https://www.research.ibm.com/people/m/michael/podc-1996.pdf | |
98 std::atomic<uint32_t> tailptr; // Last block available for iteration. | |
99 BlockHeader queue; // Empty block for linked-list head/tail. (must be last) | |
100 }; | |
101 | |
102 // The "queue" block header is used to detect "last node" so that zero/null | |
103 // can be used to indicate that it hasn't been added at all. It is part of | |
104 // the SharedMetadata structure which itself is always located at offset zero. | |
105 const PersistentMemoryAllocator::Reference | |
106 PersistentMemoryAllocator::kReferenceQueue = | |
107 offsetof(SharedMetadata, queue); | |
108 const PersistentMemoryAllocator::Reference | |
109 PersistentMemoryAllocator::kReferenceNull = 0; | |
110 | |
111 PersistentMemoryAllocator::PersistentMemoryAllocator(void* base, | |
112 size_t size, | |
113 size_t page_size, | |
114 const std::string& name) | |
115 : mem_base_(static_cast<char*>(base)), | |
116 mem_size_(static_cast<uint32_t>(size)), | |
117 mem_page_(static_cast<uint32_t>((page_size ? page_size : size))), | |
118 corrupt_(0), | |
119 allocs_histogram_(nullptr), | |
120 used_histogram_(nullptr) { | |
121 static_assert(sizeof(BlockHeader) % kAllocAlignment == 0, | |
122 "BlockHeader is not a multiple of kAllocAlignment"); | |
123 static_assert(sizeof(SharedMetadata) % kAllocAlignment == 0, | |
124 "SharedMetadata is not a multiple of kAllocAlignment"); | |
125 | |
126 CHECK(base && reinterpret_cast<uintptr_t>(base) % kAllocAlignment == 0); | |
127 CHECK(size >= kSegmentMinSize && size <= kSegmentMaxSize && | |
128 size % kAllocAlignment == 0); | |
129 CHECK(page_size == 0 || size % page_size == 0); | |
130 | |
131 // These atomics operate inter-process and so must be lock-free. The local | |
132 // casts are to make sure it can be evaluated at compile time to a constant. | |
133 CHECK(((SharedMetadata*)0)->freeptr.is_lock_free()); | |
134 CHECK(((SharedMetadata*)0)->flags.is_lock_free()); | |
135 CHECK(((BlockHeader*)0)->next.is_lock_free()); | |
136 CHECK(corrupt_.is_lock_free()); // Inter-process so must be lock-free. | |
137 | |
138 if (shared_meta()->cookie != kGlobalCookie) { | |
139 // This block is only executed when a completely new memory segment is | |
140 // being initialized. It's unshared and single-threaded... | |
141 volatile BlockHeader* const first_block = | |
142 reinterpret_cast<volatile BlockHeader*>(mem_base_ + | |
143 sizeof(SharedMetadata)); | |
144 if (shared_meta()->cookie != 0 || | |
145 shared_meta()->size != 0 || | |
146 shared_meta()->version != 0 || | |
147 shared_meta()->freeptr.load() != 0 || | |
148 shared_meta()->flags.load() != 0 || | |
149 shared_meta()->name != 0 || | |
150 shared_meta()->tailptr != 0 || | |
151 shared_meta()->queue.cookie != 0 || | |
152 shared_meta()->queue.next.load() != 0 || | |
153 first_block->size != 0 || | |
154 first_block->cookie != 0 || | |
155 first_block->type_id != 0 || | |
156 first_block->next != 0) { | |
157 // ...or something malicious has been playing with the metadata. | |
158 NOTREACHED(); | |
159 SetCorrupt(); | |
160 } | |
161 | |
162 // This is still safe to do even if corruption has been detected. | |
163 shared_meta()->cookie = kGlobalCookie; | |
164 shared_meta()->size = mem_size_; | |
165 shared_meta()->page_size = mem_page_; | |
166 shared_meta()->version = kGlobalVersion; | |
167 shared_meta()->freeptr.store(sizeof(SharedMetadata)); | |
168 | |
169 // Set up the queue of iterable allocations. | |
170 shared_meta()->queue.size = sizeof(BlockHeader); | |
171 shared_meta()->queue.cookie = kBlockCookieQueue; | |
172 shared_meta()->queue.next.store(kReferenceQueue); | |
173 shared_meta()->tailptr.store(kReferenceQueue); | |
174 | |
175 // Allocate space for the name so other processes can learn it. | |
176 if (!name.empty()) { | |
177 const size_t name_length = name.length() + 1; | |
178 shared_meta()->name = Allocate(name_length, 0); | |
179 char* name_cstr = GetAsObject<char>(shared_meta()->name, 0); | |
180 if (name_cstr) | |
181 strcpy(name_cstr, name.c_str()); | |
182 } | |
183 } else { | |
184 // The allocator is attaching to a previously initialized segment of | |
185 // memory. Make sure the embedded data matches what has been passed. | |
186 if (shared_meta()->size != mem_size_ || | |
187 shared_meta()->page_size != mem_page_) { | |
188 NOTREACHED(); | |
189 SetCorrupt(); | |
190 } | |
191 } | |
192 | |
193 // Metrics are created here so there is no recursion from Allocate | |
194 // trying to update a histogram that needs to be created and in turn | |
195 // calls Allocate again. | |
196 // Some metrics are only active on the primary owner. | |
197 if (!name.empty()) { | |
198 used_histogram_ = Histogram::FactoryGet( | |
199 name + ".UsedKiB", 1, 256 << 10, 100, HistogramBase::kNoFlags); | |
200 } | |
201 | |
202 // Other metrics are active on all users of the memory segment. | |
203 Reference name_ref = shared_meta()->name; | |
204 char* name_cstr = GetAsObject<char>(name_ref, 0); | |
205 if (name_cstr) { | |
206 size_t name_length = GetAllocSize(name_ref); | |
207 while (name_length > 0 && name_cstr[name_length - 1] == '\0') | |
208 --name_length; | |
209 if (name_length > 0) { | |
210 std::string shared_name(name_cstr, name_length); | |
211 allocs_histogram_ = Histogram::FactoryGet( | |
212 shared_name + ".Allocs", 1, 10000, 50, HistogramBase::kNoFlags); | |
213 } | |
214 } | |
215 } | |
216 | |
217 PersistentMemoryAllocator::~PersistentMemoryAllocator() { | |
218 // It's strictly forbidden to do any memory access here in case there is | |
219 // some issue with the underlying memory segment. The "Local" allocator | |
220 // makes use of this to allow deletion of the segment on the heap from | |
221 // within its destructor. | |
222 } | |
223 | |
224 size_t PersistentMemoryAllocator::GetAllocSize(Reference ref) { | |
225 volatile BlockHeader* const block = GetBlock(ref, 0, 0, false, false); | |
226 if (!block) | |
227 return 0; | |
228 uint32_t size = block->size; | |
229 // Header was verified by GetBlock() but a malicious actor could change | |
230 // the value between there and here. Check it again. | |
231 if (size <= sizeof(BlockHeader) || ref + size >= mem_size_) | |
232 return 0; | |
233 return size - sizeof(BlockHeader); | |
234 } | |
235 | |
236 uint32_t PersistentMemoryAllocator::GetType(Reference ref) { | |
237 volatile BlockHeader* const block = GetBlock(ref, 0, 0, false, false); | |
238 if (!block) | |
239 return 0; | |
240 return block->type_id; | |
241 } | |
242 | |
243 void PersistentMemoryAllocator::SetType(Reference ref, uint32_t type_id) { | |
244 volatile BlockHeader* const block = GetBlock(ref, 0, 0, false, false); | |
245 if (!block) | |
246 return; | |
247 block->type_id = type_id; | |
248 } | |
249 | |
250 PersistentMemoryAllocator::Reference PersistentMemoryAllocator::Allocate( | |
251 size_t req_size, | |
252 uint32_t type_id) { | |
253 // Validate req_size to ensure it won't overflow when used as 32-bit value. | |
254 if (req_size > kSegmentMaxSize - sizeof(BlockHeader)) { | |
255 NOTREACHED(); | |
256 return kReferenceNull; | |
257 } | |
258 | |
259 // Round up the requested size, plus header, to the next allocation alignment. | |
260 uint32_t size = static_cast<uint32_t>(req_size + sizeof(BlockHeader)); | |
261 size = (size + (kAllocAlignment - 1)) & ~(kAllocAlignment - 1); | |
262 if (size <= sizeof(BlockHeader) || size > mem_page_) { | |
263 NOTREACHED(); | |
264 return kReferenceNull; | |
265 } | |
266 | |
267 // Get the current start of unallocated memory. Other threads may | |
268 // update this at any time and cause us to retry these operations. | |
269 // This value should be treated as "const" to avoid confusion through | |
270 // the code below but recognize that any failed compare-exchange operation | |
271 // involving it will cause it to be loaded with a more recent value. The | |
272 // code should either exit or restart the loop in that case. | |
273 /* const */ uint32_t freeptr = shared_meta()->freeptr.load(); | |
274 | |
275 // Allocation is lockless so we do all our caculation and then, if saving | |
276 // indicates a change has occurred since we started, scrap everything and | |
277 // start over. | |
278 for (;;) { | |
279 if (IsCorrupt()) | |
280 return kReferenceNull; | |
281 | |
282 if (freeptr + size > mem_size_) { | |
283 SetFlag(&shared_meta()->flags, kFlagFull); | |
284 return kReferenceNull; | |
285 } | |
286 | |
287 // Get pointer to the "free" block. It doesn't even have a header; pass | |
288 // -sizeof(header) so accouting for that will yield an expected size of | |
Dmitry Vyukov
2015/12/03 20:51:37
We don't pass -sizeof(header) anymore.
bcwhite
2015/12/03 21:53:41
Heh. The fun of documentation. Fixed.
| |
289 // zero which is what will be stored at that location. If something | |
290 // has been allocated since the load of freeptr above, it is still safe | |
291 // as nothing will be written to that location until after the CAS below. | |
292 volatile BlockHeader* const block = GetBlock(freeptr, 0, 0, false, true); | |
293 if (!block) { | |
294 SetCorrupt(); | |
295 return kReferenceNull; | |
296 } | |
297 | |
298 // An allocation cannot cross page boundaries. If it would, create a | |
299 // "wasted" block and begin again at the top of the next page. This | |
300 // area could just be left empty but we fill in the block header just | |
301 // for completeness sake. | |
302 const uint32_t page_free = mem_page_ - freeptr % mem_page_; | |
303 if (size > page_free) { | |
304 if (page_free <= sizeof(BlockHeader)) { | |
305 SetCorrupt(); | |
306 return kReferenceNull; | |
307 } | |
308 const uint32_t new_freeptr = freeptr + page_free; | |
309 if (shared_meta()->freeptr.compare_exchange_strong(freeptr, | |
310 new_freeptr)) { | |
311 block->size = page_free; | |
312 block->cookie = kBlockCookieWasted; | |
313 } | |
314 continue; | |
315 } | |
316 | |
317 // Don't leave a slice at the end of a page too small for anything. This | |
318 // can result in an allocation up to two alignment-sizes greater than the | |
319 // minimum required by requested-size + header + alignment. | |
320 if (page_free - size < sizeof(BlockHeader) + kAllocAlignment) | |
321 size = page_free; | |
322 | |
323 const uint32_t new_freeptr = freeptr + size; | |
324 if (new_freeptr > mem_size_) { | |
325 SetCorrupt(); | |
326 return kReferenceNull; | |
327 } | |
328 | |
329 // Save our work. Try again if another thread has completed an allocation | |
330 // while we were processing. A "weak" exchange would be permissable here | |
331 // because the code will just loop and try again but the above processing | |
332 // is significant so make the extra effort of a "strong" exchange. | |
333 if (!shared_meta()->freeptr.compare_exchange_strong(freeptr, new_freeptr)) | |
334 continue; | |
335 | |
336 // Record this allocation in usage stats (if active). This is safe | |
337 // to call at this point because the allocation is complete. | |
338 if (allocs_histogram_) | |
339 allocs_histogram_->Add(static_cast<HistogramBase::Sample>(req_size)); | |
340 | |
341 // Given that all memory was zeroed before ever being given to an instance | |
342 // of this class and given that we only allocate in a monotomic fashion | |
343 // going forward, it must be that the newly allocated block is completely | |
344 // full of zeros. If we find anything in the block header that is NOT a | |
345 // zero then something must have previously run amuck through memory, | |
346 // writing beyond the allocated space and into unallocated space. | |
347 if (block->size != 0 || | |
348 block->cookie != kBlockCookieFree || | |
349 block->type_id != 0 || | |
350 block->next.load() != 0) { | |
351 SetCorrupt(); | |
352 return kReferenceNull; | |
353 } | |
354 | |
355 block->size = size; | |
356 block->cookie = kBlockCookieAllocated; | |
357 block->type_id = type_id; | |
358 return freeptr; | |
359 } | |
360 } | |
361 | |
362 void PersistentMemoryAllocator::GetMemoryInfo(MemoryInfo* meminfo) { | |
363 uint32_t remaining = mem_size_ - shared_meta()->freeptr.load(); | |
364 meminfo->total = mem_size_; | |
365 meminfo->free = IsCorrupt() ? 0 : remaining - sizeof(BlockHeader); | |
366 } | |
367 | |
368 void PersistentMemoryAllocator::MakeIterable(Reference ref) { | |
369 if (IsCorrupt()) | |
370 return; | |
371 volatile BlockHeader* block = GetBlock(ref, 0, 0, false, false); | |
372 if (!block) // invalid reference | |
373 return; | |
374 if (block->next.load(std::memory_order_acquire) != 0) // Already iterable. | |
375 return; | |
376 block->next.store(kReferenceQueue, std::memory_order_release); // New tail. | |
377 | |
378 // Try to add this block to the tail of the queue. May take multiple tries. | |
379 // If so, tail will be automatically updated with a more recent value during | |
380 // compare-exchange operations. | |
381 uint32_t tail = shared_meta()->tailptr.load(std::memory_order_acquire); | |
382 for (;;) { | |
383 // Acquire the current tail-pointer released by previous call to this | |
384 // method and validate it. | |
385 block = GetBlock(tail, 0, 0, true, false); | |
386 if (!block) { | |
387 SetCorrupt(); | |
388 return; | |
389 } | |
390 | |
391 // Try to insert the block at the tail of the queue. The tail node always | |
392 // has an existing value of kReferenceQueue; if that is somehow not the | |
393 // existing value then another thread has acted in the meantime. | |
394 uint32_t next = kReferenceQueue; // Will get replaced with existing value. | |
395 if (block->next.compare_exchange_strong(next, ref, | |
Dmitry Vyukov
2015/12/03 20:51:37
Since this file is so rich with comments and you h
bcwhite
2015/12/03 21:53:41
Done.
| |
396 std::memory_order_release, | |
397 std::memory_order_acquire)) { | |
398 // Update the tail pointer to the new offset. If the "else" clause did | |
399 // not exist, then this could be a simple Release_Store to set the new | |
400 // value but because it does, it's possible that other threads could add | |
401 // one or more nodes at the tail before reaching this point. We don't | |
402 // have to check the return value because it either operates correctly | |
403 // or the exact same operation has already been done (by the "else" | |
404 // clause) on some other thread. | |
405 shared_meta()->tailptr.compare_exchange_strong(tail, ref, | |
406 std::memory_order_release, | |
407 std::memory_order_relaxed); | |
408 return; | |
409 } else { | |
410 // In the unlikely case that a thread crashed or was killed between the | |
411 // update of "next" and the update of "tailptr", it is necessary to | |
412 // perform the operation that would have been done. There's no explicit | |
413 // check for crash/kill which means that this operation may also happen | |
414 // even when the other thread is in perfect working order which is what | |
415 // necessitates the CompareAndSwap above. | |
416 shared_meta()->tailptr.compare_exchange_strong(tail, next, | |
417 std::memory_order_release, | |
418 std::memory_order_acquire); | |
Dmitry Vyukov
2015/12/03 20:51:37
FWIW, the holy standard says:
20.7.2.5
template
bcwhite
2015/12/03 21:53:41
Done. Of note, the standard also says...
http://e
| |
419 } | |
420 } | |
421 } | |
422 | |
423 void PersistentMemoryAllocator::CreateIterator(Iterator* state) { | |
424 state->last = kReferenceQueue; | |
425 state->niter = 0; | |
426 } | |
427 | |
428 PersistentMemoryAllocator::Reference PersistentMemoryAllocator::GetNextIterable( | |
429 Iterator* state, | |
430 uint32_t* type_id) { | |
431 volatile BlockHeader* block = GetBlock(state->last, 0, 0, true, false); | |
432 if (!block) // invalid iterator state | |
433 return kReferenceNull; | |
434 | |
435 // The compiler and CPU can freely reorder all memory accesses on which | |
436 // there are no dependencies. It could, for example, move the load of | |
437 // "freeptr" above this point because there are no explicit dependencies | |
438 // between it and "next". If it did, however, then another block could | |
439 // be queued after that but before the following load meaning there is | |
440 // one more queued block than the future "detect loop by having more | |
441 // blocks that could fit before freeptr" will allow. | |
442 // | |
443 // By "acquiring" the "next" value here, it's synchronized to the enqueue | |
444 // of the node which in turn is synchronized to the allocation (which sets | |
445 // freeptr). Thus, the scenario above cannot happen. | |
446 uint32_t next = block->next.load(std::memory_order_acquire); | |
447 block = GetBlock(next, 0, 0, false, false); | |
448 if (!block) // no next allocation in queue | |
449 return kReferenceNull; | |
450 | |
451 // Memory corruption could cause a loop in the list. We need to detect | |
452 // that so as to not cause an infinite loop in the caller. We do this | |
453 // simply by making sure we don't iterate more than the absolute maximum | |
454 // number of allocations that could have been made. Callers are likely | |
455 // to loop multiple times before it is detected but at least it stops. | |
456 uint32_t freeptr = std::min( | |
457 shared_meta()->freeptr.load(std::memory_order_acquire), | |
458 mem_size_); | |
459 if (state->niter > freeptr / (sizeof(BlockHeader) + kAllocAlignment)) { | |
460 SetCorrupt(); | |
461 return kReferenceNull; | |
462 } | |
463 | |
464 state->last = next; | |
465 state->niter++; | |
466 *type_id = block->type_id; | |
467 | |
468 return next; | |
469 } | |
470 | |
471 // The "corrupted" state is held both locally and globally (shared). The | |
472 // shared flag can't be trusted since a malicious actor could overwrite it. | |
473 // The local version is immune to foreign actors. Thus, if seen shared, | |
474 // copy it locally and, once known, always restore it globally. | |
475 void PersistentMemoryAllocator::SetCorrupt() { | |
476 LOG(ERROR) << "Corruption detected in shared-memory segment."; | |
477 corrupt_.store(true); | |
478 SetFlag(&shared_meta()->flags, kFlagCorrupt); | |
479 } | |
480 | |
481 bool PersistentMemoryAllocator::IsCorrupt() { | |
482 if (corrupt_.load() || CheckFlag(&shared_meta()->flags, kFlagCorrupt)) { | |
483 SetCorrupt(); // Make sure all indicators are set. | |
484 return true; | |
485 } | |
486 return false; | |
487 } | |
488 | |
489 bool PersistentMemoryAllocator::IsFull() { | |
490 return CheckFlag(&shared_meta()->flags, kFlagFull); | |
491 } | |
492 | |
493 // Dereference a block |ref| and ensure that it's valid for the desired | |
494 // |type_id| and |size|. |special| indicates that we may try to access block | |
495 // headers not available to callers but still accessed by this module. By | |
496 // having internal dereferences go through this same function, the allocator | |
497 // is hardened against corruption. | |
498 volatile PersistentMemoryAllocator::BlockHeader* | |
499 PersistentMemoryAllocator::GetBlock(Reference ref, uint32_t type_id, | |
500 uint32_t size, bool queue_ok, | |
501 bool free_ok) { | |
502 // Validation of parameters. | |
503 if (ref % kAllocAlignment != 0) | |
504 return nullptr; | |
505 if (ref < (queue_ok ? kReferenceQueue : sizeof(SharedMetadata))) | |
506 return nullptr; | |
507 size += sizeof(BlockHeader); | |
508 if (ref + size > mem_size_) | |
509 return nullptr; | |
510 | |
511 // Validation of referenced block-header. | |
512 if (!free_ok) { | |
513 uint32_t freeptr = shared_meta()->freeptr.load(); | |
514 if (ref + size > freeptr) | |
515 return nullptr; | |
516 volatile BlockHeader* const block = | |
517 reinterpret_cast<volatile BlockHeader*>(mem_base_ + ref); | |
518 if (block->size < size) | |
519 return nullptr; | |
520 if (ref != kReferenceQueue && block->cookie != kBlockCookieAllocated) | |
521 return nullptr; | |
522 if (type_id != 0 && block->type_id != type_id) | |
523 return nullptr; | |
524 } | |
525 | |
526 // Return pointer to block data. | |
527 return reinterpret_cast<volatile BlockHeader*>(mem_base_ + ref); | |
528 } | |
529 | |
530 volatile void* PersistentMemoryAllocator::GetBlockData(Reference ref, | |
531 uint32_t type_id, | |
532 uint32_t size) { | |
533 DCHECK(size > 0); | |
534 volatile BlockHeader* block = GetBlock(ref, type_id, size, false, false); | |
535 if (!block) | |
536 return nullptr; | |
537 return reinterpret_cast<volatile char*>(block) + sizeof(BlockHeader); | |
538 } | |
539 | |
540 void PersistentMemoryAllocator::UpdateStaticHistograms() { | |
541 if (used_histogram_) { | |
542 MemoryInfo meminfo; | |
543 GetMemoryInfo(&meminfo); | |
544 HistogramBase::Sample usedkb = static_cast<HistogramBase::Sample>( | |
545 (meminfo.total - meminfo.free) >> 10); | |
546 used_histogram_->Add(usedkb); | |
547 } | |
548 } | |
549 | |
550 //----- LocalPersistentMemoryAllocator ----------------------------------------- | |
551 | |
552 LocalPersistentMemoryAllocator::LocalPersistentMemoryAllocator( | |
553 size_t size, | |
554 const std::string& name) | |
555 : PersistentMemoryAllocator(memset(new char[size], 0, size), | |
556 size, 0, name) {} | |
557 | |
558 LocalPersistentMemoryAllocator::~LocalPersistentMemoryAllocator() { | |
559 delete mem_base_; | |
560 } | |
561 | |
562 } // namespace base | |
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