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1 // Copyright 2014 The Chromium Authors. All rights reserved. | 1 // Copyright 2014 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "base/memory/discardable_shared_memory.h" | 5 #include "base/memory/discardable_shared_memory.h" |
6 | 6 |
7 #if defined(OS_POSIX) | 7 #if defined(OS_POSIX) && !defined(OS_NACL) |
danakj
2015/10/20 18:04:03
I'm still kinda uncomfortable with this statement
reveman
2015/10/21 14:50:57
madvise() is part of the POSIX standard. It was ad
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8 #include <unistd.h> | 8 #include <sys/mman.h> |
9 #endif | 9 #endif |
10 | 10 |
11 #include <algorithm> | 11 #include <algorithm> |
12 | 12 |
13 #include "base/atomicops.h" | 13 #include "base/atomicops.h" |
14 #include "base/bits.h" | 14 #include "base/bits.h" |
15 #include "base/logging.h" | 15 #include "base/logging.h" |
16 #include "base/numerics/safe_math.h" | 16 #include "base/numerics/safe_math.h" |
17 #include "base/process/process_metrics.h" | 17 #include "base/process/process_metrics.h" |
18 | 18 |
19 #if defined(OS_ANDROID) | 19 #if defined(OS_ANDROID) |
20 #include "third_party/ashmem/ashmem.h" | 20 #include "third_party/ashmem/ashmem.h" |
21 #endif | 21 #endif |
22 | 22 |
23 // Use MADV_FREE when MADV_REMOVE is not available. MADV_FREE doesn't give us | |
Primiano Tucci (use gerrit)
2015/10/20 13:33:39
I'd probably make this comment a bit more explicit
reveman
2015/10/21 14:50:57
Done.
| |
24 // the guarantee that pages will be zero-filled after a call which makes it | |
25 // hard to test but it shouldn't hurt to use it. Worst case, it has the effect | |
26 // of not calling madvise. | |
27 #if !defined(DISCARDABLE_SHARED_MEMORY_REMOVE) | |
28 #define MADV_REMOVE MADV_FREE | |
29 #endif | |
30 | |
23 namespace base { | 31 namespace base { |
24 namespace { | 32 namespace { |
25 | 33 |
26 // Use a machine-sized pointer as atomic type. It will use the Atomic32 or | 34 // Use a machine-sized pointer as atomic type. It will use the Atomic32 or |
27 // Atomic64 routines, depending on the architecture. | 35 // Atomic64 routines, depending on the architecture. |
28 typedef intptr_t AtomicType; | 36 typedef intptr_t AtomicType; |
29 typedef uintptr_t UAtomicType; | 37 typedef uintptr_t UAtomicType; |
30 | 38 |
31 // Template specialization for timestamp serialization/deserialization. This | 39 // Template specialization for timestamp serialization/deserialization. This |
32 // is used to serialize timestamps using Unix time on systems where AtomicType | 40 // is used to serialize timestamps using Unix time on systems where AtomicType |
(...skipping 261 matching lines...) Expand 10 before | Expand all | Expand 10 after Loading... | |
294 } | 302 } |
295 | 303 |
296 void* DiscardableSharedMemory::memory() const { | 304 void* DiscardableSharedMemory::memory() const { |
297 return reinterpret_cast<uint8*>(shared_memory_.memory()) + | 305 return reinterpret_cast<uint8*>(shared_memory_.memory()) + |
298 AlignToPageSize(sizeof(SharedState)); | 306 AlignToPageSize(sizeof(SharedState)); |
299 } | 307 } |
300 | 308 |
301 bool DiscardableSharedMemory::Purge(Time current_time) { | 309 bool DiscardableSharedMemory::Purge(Time current_time) { |
302 // Calls to this function must be synchronized properly. | 310 // Calls to this function must be synchronized properly. |
303 DFAKE_SCOPED_LOCK(thread_collision_warner_); | 311 DFAKE_SCOPED_LOCK(thread_collision_warner_); |
304 | 312 DCHECK(shared_memory_.memory()); |
305 // Early out if not mapped. This can happen if the segment was previously | |
306 // unmapped using a call to Close(). | |
307 if (!shared_memory_.memory()) | |
308 return true; | |
309 | 313 |
310 SharedState old_state(SharedState::UNLOCKED, last_known_usage_); | 314 SharedState old_state(SharedState::UNLOCKED, last_known_usage_); |
311 SharedState new_state(SharedState::UNLOCKED, Time()); | 315 SharedState new_state(SharedState::UNLOCKED, Time()); |
312 SharedState result(subtle::Acquire_CompareAndSwap( | 316 SharedState result(subtle::Acquire_CompareAndSwap( |
313 &SharedStateFromSharedMemory(shared_memory_)->value.i, | 317 &SharedStateFromSharedMemory(shared_memory_)->value.i, |
314 old_state.value.i, | 318 old_state.value.i, |
315 new_state.value.i)); | 319 new_state.value.i)); |
316 | 320 |
317 // Update |last_known_usage_| to |current_time| if the memory is locked. This | 321 // Update |last_known_usage_| to |current_time| if the memory is locked. This |
318 // allows the caller to determine if purging failed because last known usage | 322 // allows the caller to determine if purging failed because last known usage |
319 // was incorrect or memory was locked. In the second case, the caller should | 323 // was incorrect or memory was locked. In the second case, the caller should |
320 // most likely wait for some amount of time before attempting to purge the | 324 // most likely wait for some amount of time before attempting to purge the |
321 // the memory again. | 325 // the memory again. |
322 if (result.value.u != old_state.value.u) { | 326 if (result.value.u != old_state.value.u) { |
323 last_known_usage_ = result.GetLockState() == SharedState::LOCKED | 327 last_known_usage_ = result.GetLockState() == SharedState::LOCKED |
324 ? current_time | 328 ? current_time |
325 : result.GetTimestamp(); | 329 : result.GetTimestamp(); |
326 return false; | 330 return false; |
327 } | 331 } |
328 | 332 |
333 #if defined(OS_POSIX) && !defined(OS_NACL) | |
334 // Advise the kernel to remove resources associated with purged pages. | |
335 // Subsequent accesses of memory pages will succeed, but will result in | |
336 // zero-fill-on-demand pages. | |
337 if (madvise(reinterpret_cast<char*>(shared_memory_.memory()) + | |
338 AlignToPageSize(sizeof(SharedState)), | |
339 AlignToPageSize(mapped_size_), MADV_REMOVE)) { | |
340 DPLOG(ERROR) << "madvise(MADV_REMOVE) failed"; | |
Primiano Tucci (use gerrit)
2015/10/20 13:33:39
On mac if this fails you will say that madvise(MAD
reveman
2015/10/21 14:50:57
Done.
| |
341 } | |
342 #endif | |
343 | |
329 last_known_usage_ = Time(); | 344 last_known_usage_ = Time(); |
330 return true; | 345 return true; |
331 } | 346 } |
332 | 347 |
333 bool DiscardableSharedMemory::IsMemoryResident() const { | 348 bool DiscardableSharedMemory::IsMemoryResident() const { |
334 DCHECK(shared_memory_.memory()); | 349 DCHECK(shared_memory_.memory()); |
335 | 350 |
336 SharedState result(subtle::NoBarrier_Load( | 351 SharedState result(subtle::NoBarrier_Load( |
337 &SharedStateFromSharedMemory(shared_memory_)->value.i)); | 352 &SharedStateFromSharedMemory(shared_memory_)->value.i)); |
338 | 353 |
339 return result.GetLockState() == SharedState::LOCKED || | 354 return result.GetLockState() == SharedState::LOCKED || |
340 !result.GetTimestamp().is_null(); | 355 !result.GetTimestamp().is_null(); |
341 } | 356 } |
342 | 357 |
343 bool DiscardableSharedMemory::IsMemoryLocked() const { | 358 bool DiscardableSharedMemory::IsMemoryLocked() const { |
344 DCHECK(shared_memory_.memory()); | 359 DCHECK(shared_memory_.memory()); |
345 | 360 |
346 SharedState result(subtle::NoBarrier_Load( | 361 SharedState result(subtle::NoBarrier_Load( |
347 &SharedStateFromSharedMemory(shared_memory_)->value.i)); | 362 &SharedStateFromSharedMemory(shared_memory_)->value.i)); |
348 | 363 |
349 return result.GetLockState() == SharedState::LOCKED; | 364 return result.GetLockState() == SharedState::LOCKED; |
350 } | 365 } |
351 | 366 |
352 void DiscardableSharedMemory::Close() { | 367 void DiscardableSharedMemory::Close() { |
353 shared_memory_.Close(); | 368 shared_memory_.Close(); |
354 } | 369 } |
355 | 370 |
356 #if defined(DISCARDABLE_SHARED_MEMORY_SHRINKING) | |
357 void DiscardableSharedMemory::Shrink() { | |
358 #if defined(OS_POSIX) | |
359 SharedMemoryHandle handle = shared_memory_.handle(); | |
360 if (!SharedMemory::IsHandleValid(handle)) | |
361 return; | |
362 | |
363 // Truncate shared memory to size of SharedState. | |
364 if (HANDLE_EINTR(ftruncate(SharedMemory::GetFdFromSharedMemoryHandle(handle), | |
365 AlignToPageSize(sizeof(SharedState)))) != 0) { | |
366 DPLOG(ERROR) << "ftruncate() failed"; | |
367 return; | |
368 } | |
369 mapped_size_ = 0; | |
370 #else | |
371 NOTIMPLEMENTED(); | |
372 #endif | |
373 } | |
374 #endif | |
375 | |
376 Time DiscardableSharedMemory::Now() const { | 371 Time DiscardableSharedMemory::Now() const { |
377 return Time::Now(); | 372 return Time::Now(); |
378 } | 373 } |
379 | 374 |
380 } // namespace base | 375 } // namespace base |
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