diff options
Diffstat (limited to 'base/metrics/persistent_memory_allocator.h')
| -rw-r--r-- | base/metrics/persistent_memory_allocator.h | 47 |
1 files changed, 46 insertions, 1 deletions
diff --git a/base/metrics/persistent_memory_allocator.h b/base/metrics/persistent_memory_allocator.h index b38f284ff4..94a7744bfb 100644 --- a/base/metrics/persistent_memory_allocator.h +++ b/base/metrics/persistent_memory_allocator.h @@ -96,6 +96,29 @@ class BASE_EXPORT PersistentMemoryAllocator { public: typedef uint32_t Reference; + // These states are used to indicate the overall condition of the memory + // segment irrespective of what is stored within it. Because the data is + // often persistent and thus needs to be readable by different versions of + // a program, these values are fixed and can never change. + enum MemoryState : uint8_t { + // Persistent memory starts all zeros and so shows "uninitialized". + MEMORY_UNINITIALIZED = 0, + + // The header has been written and the memory is ready for use. + MEMORY_INITIALIZED = 1, + + // The data should be considered deleted. This would be set when the + // allocator is being cleaned up. If file-backed, the file is likely + // to be deleted but since deletion can fail for a variety of reasons, + // having this extra status means a future reader can realize what + // should have happened. + MEMORY_DELETED = 2, + + // Outside code can create states starting with this number; these too + // must also never change between code versions. + MEMORY_USER_DEFINED = 100, + }; + // Iterator for going through all iterable memory records in an allocator. // Like the allocator itself, iterators are lock-free and thread-secure. // That means that multiple threads can share an iterator and the same @@ -280,7 +303,11 @@ class BASE_EXPORT PersistentMemoryAllocator { const char* Name() const; // Is this segment open only for read? - bool IsReadonly() { return readonly_; } + bool IsReadonly() const { return readonly_; } + + // Manage the saved state of the memory. + void SetMemoryState(uint8_t memory_state); + uint8_t GetMemoryState() const; // Create internal histograms for tracking memory use and allocation sizes // for allocator of |name| (which can simply be the result of Name()). This @@ -293,6 +320,17 @@ class BASE_EXPORT PersistentMemoryAllocator { // UMA.PersistentAllocator.name.UsedPct void CreateTrackingHistograms(base::StringPiece name); + // Flushes the persistent memory to any backing store. This typically does + // nothing but is used by the FilePersistentMemoryAllocator to inform the + // OS that all the data should be sent to the disk immediately. This is + // useful in the rare case where something has just been stored that needs + // to survive a hard shutdown of the machine like from a power failure. + // The |sync| parameter indicates if this call should block until the flush + // is complete but is only advisory and may or may not have an effect + // depending on the capabilities of the OS. Synchronous flushes are allowed + // only from theads that are allowed to do I/O. + void Flush(bool sync); + // Direct access to underlying memory segment. If the segment is shared // across threads or processes, reading data through these values does // not guarantee consistency. Use with care. Do not write. @@ -580,6 +618,9 @@ class BASE_EXPORT PersistentMemoryAllocator { uint64_t id, base::StringPiece name, bool readonly); + // Implementation of Flush that accepts how much to flush. + virtual void FlushPartial(size_t length, bool sync); + volatile char* const mem_base_; // Memory base. (char so sizeof guaranteed 1) const MemoryType mem_type_; // Type of memory allocation. const uint32_t mem_size_; // Size of entire memory segment. @@ -715,6 +756,10 @@ class BASE_EXPORT FilePersistentMemoryAllocator // the rest. static bool IsFileAcceptable(const MemoryMappedFile& file, bool read_only); + protected: + // PersistentMemoryAllocator: + void FlushPartial(size_t length, bool sync) override; + private: std::unique_ptr<MemoryMappedFile> mapped_file_; |