diff options
Diffstat (limited to 'src/mongo/db/storage/mmap_v1/record_access_tracker.h')
| -rw-r--r-- | src/mongo/db/storage/mmap_v1/record_access_tracker.h | 199 |
1 files changed, 99 insertions, 100 deletions
diff --git a/src/mongo/db/storage/mmap_v1/record_access_tracker.h b/src/mongo/db/storage/mmap_v1/record_access_tracker.h index aa98e22230e..a1cb7ab2187 100644 --- a/src/mongo/db/storage/mmap_v1/record_access_tracker.h +++ b/src/mongo/db/storage/mmap_v1/record_access_tracker.h @@ -33,127 +33,126 @@ namespace mongo { - class MmapV1RecordHeader; +class MmapV1RecordHeader; + +/** + * Used to implement likelyInPhysicalMemory() for the MMAP v1 storage engine. Since + * MMAP v1 holds exclusive collection-level locks, it should yield the locks during a + * page fault. The RecordAccessTracker is used to guess at which records are in memory, + * so that a yield can be requested unless we're sure that the record has been + * recently accessed. + */ +class RecordAccessTracker { + MONGO_DISALLOW_COPYING(RecordAccessTracker); + +public: + RecordAccessTracker(); + + enum Constants { + SliceSize = 1024, + MaxChain = 20, // intentionally very low + NumSlices = 10, + RotateTimeSecs = 90, + BigHashSize = 128 + }; /** - * Used to implement likelyInPhysicalMemory() for the MMAP v1 storage engine. Since - * MMAP v1 holds exclusive collection-level locks, it should yield the locks during a - * page fault. The RecordAccessTracker is used to guess at which records are in memory, - * so that a yield can be requested unless we're sure that the record has been - * recently accessed. + * Informs this record access tracker that 'record' has been accessed. */ - class RecordAccessTracker { - MONGO_DISALLOW_COPYING(RecordAccessTracker); - public: - RecordAccessTracker(); + void markAccessed(const void* record); - enum Constants { - SliceSize = 1024, - MaxChain = 20, // intentionally very low - NumSlices = 10, - RotateTimeSecs = 90, - BigHashSize = 128 - }; + /** + * @return whether or not 'record' has been marked as accessed recently. A return value + * of true means that 'record' is likely in physical memory. + * + * Also has the side effect of marking 'record' as accessed. + */ + bool checkAccessedAndMark(const void* record); - /** - * Informs this record access tracker that 'record' has been accessed. - */ - void markAccessed(const void* record); + /** + * Clears out any history of record accesses. + */ + void reset(); - /** - * @return whether or not 'record' has been marked as accessed recently. A return value - * of true means that 'record' is likely in physical memory. - * - * Also has the side effect of marking 'record' as accessed. - */ - bool checkAccessedAndMark(const void* record); + // + // For testing. + // + + /** + * The accessedRecently() implementation falls back to making a system call if it + * appears that the record is not in physical memory. Use this method to disable + * the fallback for testing. + */ + void disableSystemBlockInMemCheck(); + +private: + enum State { In, Out, Unk }; + + struct Entry { + size_t region; + unsigned long long value; + }; + + /** + * simple hash map for region -> status + * this constitutes a single region of time + * it does chaining, but very short chains + */ + class Slice { + public: + Slice(); - /** - * Clears out any history of record accesses. - */ void reset(); - // - // For testing. - // + State get(int regionHash, size_t region, short offset); /** - * The accessedRecently() implementation falls back to making a system call if it - * appears that the record is not in physical memory. Use this method to disable - * the fallback for testing. + * @return true if added, false if full */ - void disableSystemBlockInMemCheck(); + bool put(int regionHash, size_t region, short offset); + + time_t lastReset() const; private: - enum State { - In, Out, Unk - }; + Entry* _get(int start, size_t region, bool add); + + Entry _data[SliceSize]; + time_t _lastReset; + }; - struct Entry { - size_t region; - unsigned long long value; - }; + /** + * this contains many slices of times + * the idea you put mem status in the current time slice + * and then after a certain period of time, it rolls off so we check again + */ + class Rolling { + public: + Rolling(); /** - * simple hash map for region -> status - * this constitutes a single region of time - * it does chaining, but very short chains + * After this call, we assume the page is in RAM. + * + * @param doHalf if this is a known good access, want to put in first half. + * + * @return whether we know the page is in RAM */ - class Slice { - public: - Slice(); - - void reset(); - - State get(int regionHash, size_t region, short offset); + bool access(size_t region, short offset, bool doHalf); - /** - * @return true if added, false if full - */ - bool put(int regionHash, size_t region, short offset); + private: + void _rotate(); - time_t lastReset() const; + int _curSlice; + long long _lastRotate; + Slice _slices[NumSlices]; - private: - Entry* _get(int start, size_t region, bool add); + SimpleMutex _lock; + }; - Entry _data[SliceSize]; - time_t _lastReset; - }; + // Should this record tracker fallback to making a system call? + bool _blockSupported; - /** - * this contains many slices of times - * the idea you put mem status in the current time slice - * and then after a certain period of time, it rolls off so we check again - */ - class Rolling { - public: - Rolling(); - - /** - * After this call, we assume the page is in RAM. - * - * @param doHalf if this is a known good access, want to put in first half. - * - * @return whether we know the page is in RAM - */ - bool access(size_t region, short offset, bool doHalf); - - private: - void _rotate(); - - int _curSlice; - long long _lastRotate; - Slice _slices[NumSlices]; - - SimpleMutex _lock; - }; - - // Should this record tracker fallback to making a system call? - bool _blockSupported; - - // An array of Rolling instances for tracking record accesses. - std::unique_ptr<Rolling[]> _rollingTable; - }; + // An array of Rolling instances for tracking record accesses. + std::unique_ptr<Rolling[]> _rollingTable; +}; -} // namespace +} // namespace |