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mdbx: rework MDBX_reader.

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This commit is contained in:
Leo Yuriev
2017-05-23 21:16:59 +03:00
parent a3ed42b999
commit 34213c554a
2 changed files with 42 additions and 46 deletions
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56
src/bits.h
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@@ -189,40 +189,35 @@ typedef uint16_t indx_t;
#pragma pack(push, 1)
/* The information we store in a single slot of the reader table.
* In addition to a transaction ID, we also record the process and
* thread ID that owns a slot, so that we can detect stale information,
* e.g. threads or processes that went away without cleaning up.
* NOTE: We currently don't check for stale records. We simply re-init
* the table when we know that we're the only process opening the
* lock file. */
typedef struct MDB_rxbody {
/* The actual reader record, with cacheline padding. */
typedef struct MDBX_reader {
/* Current Transaction ID when this transaction began, or (txnid_t)-1.
* Multiple readers that start at the same time will probably have the
* same ID here. Again, it's not important to exclude them from
* anything; all we need to know is which version of the DB they
* started from so we can avoid overwriting any data used in that
* particular version. */
volatile txnid_t mrb_txnid;
/* The process ID of the process owning this reader txn. */
volatile mdbx_pid_t mrb_pid;
/* The thread ID of the thread owning this txn. */
volatile mdbx_tid_t mrb_tid;
} MDB_rxbody;
volatile txnid_t mr_txnid;
/* The actual reader record, with cacheline padding. */
typedef struct MDB_reader {
union {
MDB_rxbody mrx;
/* shorthand for mrb_txnid */
#define mr_txnid mru.mrx.mrb_txnid
#define mr_pid mru.mrx.mrb_pid
#define mr_tid mru.mrx.mrb_tid
/* cache line alignment */
char pad[(sizeof(MDB_rxbody) + MDBX_CACHELINE_SIZE - 1) &
~(MDBX_CACHELINE_SIZE - 1)];
} mru;
} MDB_reader;
/* The information we store in a single slot of the reader table.
* In addition to a transaction ID, we also record the process and
* thread ID that owns a slot, so that we can detect stale information,
* e.g. threads or processes that went away without cleaning up.
*
* NOTE: We currently don't check for stale records.
* We simply re-init the table when we know that we're the only process
* opening the lock file. */
/* The process ID of the process owning this reader txn. */
volatile mdbx_pid_t mr_pid;
/* The thread ID of the thread owning this txn. */
volatile mdbx_tid_t mr_tid;
/* cache line alignment */
uint8_t pad[~(MDBX_CACHELINE_SIZE - 1) &
(sizeof(txnid_t) + sizeof(mdbx_pid_t) + sizeof(mdbx_tid_t) +
MDBX_CACHELINE_SIZE - 1)];
} MDBX_reader;
/* Information about a single database in the environment. */
typedef struct MDB_db {
@@ -345,7 +340,7 @@ typedef struct MDBX_lockinfo {
/* Mutex protecting access to this table. */
MDBX_OSAL_LOCK mti_rmutex;
#endif
MDB_reader mti_readers[1];
MDBX_reader mti_readers[1];
} MDBX_lockinfo;
#pragma pack(pop)
@@ -390,7 +385,7 @@ struct MDB_txn {
/* For write txns: Modified pages. Sorted when not MDB_WRITEMAP. */
MDB_ID2L dirty_list;
/* For read txns: This thread/txn's reader table slot, or NULL. */
MDB_reader *reader;
MDBX_reader *reader;
} mt_u;
/* Array of records for each DB known in the environment. */
MDB_dbx *mt_dbxs;
@@ -773,7 +768,8 @@ static __inline MDB_meta *mdbx_meta_head(MDB_env *env) {
void mdbx_rthc_dtor(void *rthc);
void mdbx_rthc_lock(void);
void mdbx_rthc_unlock(void);
int mdbx_rthc_alloc(mdbx_thread_key_t *key, MDB_reader *begin, MDB_reader *end);
int mdbx_rthc_alloc(mdbx_thread_key_t *key, MDBX_reader *begin,
MDBX_reader *end);
void mdbx_rthc_remove(mdbx_thread_key_t key);
void mdbx_rthc_cleanup(void);