diff options
Diffstat (limited to 'src/include/storage/buf_internals.h')
| -rw-r--r-- | src/include/storage/buf_internals.h | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h index 19247c4b2be..81aaf47da58 100644 --- a/src/include/storage/buf_internals.h +++ b/src/include/storage/buf_internals.h @@ -115,8 +115,8 @@ typedef struct buftag * Note: buf_hdr_lock must be held to examine or change the tag, flags, * usage_count, refcount, or wait_backend_pid fields. buf_id field never * changes after initialization, so does not need locking. freeNext is - * protected by the buffer_strategy_lock not buf_hdr_lock. The LWLocks can take - * care of themselves. The buf_hdr_lock is *not* used to control access to + * protected by the buffer_strategy_lock not buf_hdr_lock. The LWLock can + * take care of itself. The buf_hdr_lock is *not* used to control access to * the data in the buffer! * * An exception is that if we have the buffer pinned, its tag can't change @@ -133,22 +133,24 @@ typedef struct buftag * * We use this same struct for local buffer headers, but the lock fields * are not used and not all of the flag bits are useful either. + * + * Be careful to avoid increasing the size of the struct when adding or + * reordering members. Keeping it below 64 bytes (the most common CPU + * cache line size) is fairly important for performance. */ typedef struct BufferDesc { BufferTag tag; /* ID of page contained in buffer */ BufFlags flags; /* see bit definitions above */ - uint16 usage_count; /* usage counter for clock sweep code */ + uint8 usage_count; /* usage counter for clock sweep code */ + slock_t buf_hdr_lock; /* protects a subset of fields, see above */ unsigned refcount; /* # of backends holding pins on buffer */ int wait_backend_pid; /* backend PID of pin-count waiter */ - slock_t buf_hdr_lock; /* protects the above fields */ - int buf_id; /* buffer's index number (from 0) */ int freeNext; /* link in freelist chain */ - LWLock *io_in_progress_lock; /* to wait for I/O to complete */ - LWLock *content_lock; /* to lock access to buffer contents */ + LWLock content_lock; /* to lock access to buffer contents */ } BufferDesc; /* @@ -184,6 +186,13 @@ typedef union BufferDescPadded #define BufferDescriptorGetBuffer(bdesc) ((bdesc)->buf_id + 1) +#define BufferDescriptorGetIOLock(bdesc) \ + (&(BufferIOLWLockArray[(bdesc)->buf_id]).lock) +#define BufferDescriptorGetContentLock(bdesc) \ + ((LWLock*) (&(bdesc)->content_lock)) + +extern PGDLLIMPORT LWLockMinimallyPadded *BufferIOLWLockArray; + /* * The freeNext field is either the index of the next freelist entry, * or one of these special values: |