WT-3465 Avoid locks when reading 8-byte timestamps. (#3589)

5 files changed, 33 insertions, 34 deletions

diff --git a/src/include/txn.h b/src/include/txn.h
index f3e377b3380..e0513a82892 100644
--- a/src/include/txn.h
+++ b/src/include/txn.h
@@ -69,7 +69,6 @@ struct __wt_named_snapshot {
 
 struct __wt_txn_state {
 	WT_CACHE_LINE_PAD_BEGIN
-	WT_RWLOCK rwlock;
 	volatile uint64_t id;
 	volatile uint64_t pinned_id;
 	volatile uint64_t metadata_pinned;
diff --git a/src/include/txn.i b/src/include/txn.i
index df0bd872a6c..b37163bd78f 100644
--- a/src/include/txn.i
+++ b/src/include/txn.i
@@ -11,6 +11,8 @@ static inline void __wt_txn_read_last(WT_SESSION_IMPL *session);
 
 #ifdef HAVE_TIMESTAMPS
 #if WT_TIMESTAMP_SIZE == 8
+#define	WT_WITH_TIMESTAMP_READLOCK(session, l, e)       e
+
 /*
  * __wt_timestamp_cmp --
  *	Compare two timestamps.
@@ -61,6 +63,12 @@ __wt_timestamp_set_zero(wt_timestamp_t *ts)
 	ts->val = 0;
 }
 #else
+#define	WT_WITH_TIMESTAMP_READLOCK(s, l, e)	do {                    \
+	__wt_readlock((s), (l));                                        \
+	e;                                                              \
+	__wt_readunlock((s), (l));                                      \
+} while (0)
+
 /*
  * __wt_timestamp_cmp --
  *	Compare two timestamps.
@@ -314,9 +322,8 @@ __wt_txn_visible_all(
 	if (!txn_global->has_pinned_timestamp || timestamp == NULL)
 		return (true);
 
-	__wt_readlock(session, &txn_global->rwlock);
-	cmp = __wt_timestamp_cmp(timestamp, &txn_global->pinned_timestamp);
-	__wt_readunlock(session, &txn_global->rwlock);
+	WT_WITH_TIMESTAMP_READLOCK(session, &txn_global->rwlock,
+	    cmp = __wt_timestamp_cmp(timestamp, &txn_global->pinned_timestamp));
 
 	/*
 	 * We can discard updates with timestamps less than or equal to the
diff --git a/src/txn/txn.c b/src/txn/txn.c
index 2aec962d885..09efb2924bf 100644
--- a/src/txn/txn.c
+++ b/src/txn/txn.c
@@ -445,12 +445,11 @@ __wt_txn_config(WT_SESSION_IMPL *session, const char *cfg[])
 
 		WT_RET(__wt_txn_parse_timestamp(
 		    session, "read", &txn->read_timestamp, &cval));
-		__wt_readlock(session, &txn_global->rwlock);
-		__wt_timestamp_set(
-		    &oldest_timestamp, &txn_global->oldest_timestamp);
-		__wt_timestamp_set(
-		    &stable_timestamp, &txn_global->stable_timestamp);
-		__wt_readunlock(session, &txn_global->rwlock);
+		WT_WITH_TIMESTAMP_READLOCK(session, &txn_global->rwlock,
+		    __wt_timestamp_set(
+			&oldest_timestamp, &txn_global->oldest_timestamp);
+		    __wt_timestamp_set(
+			&stable_timestamp, &txn_global->stable_timestamp));
 		if (__wt_timestamp_cmp(
 		    &txn->read_timestamp, &oldest_timestamp) < 0)
 			WT_RET_MSG(session, EINVAL,
@@ -743,10 +742,9 @@ __wt_txn_commit(WT_SESSION_IMPL *session, const char *cfg[])
 #ifdef HAVE_TIMESTAMPS
 	/* First check if we've already committed something in the future. */
 	if (update_timestamp) {
-		__wt_readlock(session, &txn_global->rwlock);
-		__wt_timestamp_set(
-		    &prev_commit_timestamp, &txn_global->commit_timestamp);
-		__wt_readunlock(session, &txn_global->rwlock);
+		WT_WITH_TIMESTAMP_READLOCK(session, &txn_global->rwlock,
+		    __wt_timestamp_set(
+			&prev_commit_timestamp, &txn_global->commit_timestamp));
 		update_timestamp = __wt_timestamp_cmp(
 		    &txn->commit_timestamp, &prev_commit_timestamp) > 0;
 	}
diff --git a/src/txn/txn_rollback_to_stable.c b/src/txn/txn_rollback_to_stable.c
index c9c3d3247c4..e19bbc73bb3 100644
--- a/src/txn/txn_rollback_to_stable.c
+++ b/src/txn/txn_rollback_to_stable.c
@@ -38,9 +38,9 @@ __txn_rollback_to_stable_lookaside_fixup(WT_SESSION_IMPL *session)
 	 * violate protocol.
 	 */
 	txn_global = &conn->txn_global;
-	__wt_readlock(session, &txn_global->rwlock);
-	__wt_timestamp_set(&rollback_timestamp, &txn_global->stable_timestamp);
-	__wt_readunlock(session, &txn_global->rwlock);
+	WT_WITH_TIMESTAMP_READLOCK(session, &txn_global->rwlock,
+	    __wt_timestamp_set(
+		&rollback_timestamp, &txn_global->stable_timestamp));
 
 	__wt_las_cursor(session, &cursor, &session_flags);
 
@@ -347,9 +347,9 @@ __txn_rollback_to_stable_btree(
 	 * updated while rolling back, accessing it without a lock would
 	 * violate protocol.
 	 */
-	__wt_readlock(session, &txn_global->rwlock);
-	__wt_timestamp_set(&rollback_timestamp, &txn_global->stable_timestamp);
-	__wt_readunlock(session, &txn_global->rwlock);
+	WT_WITH_TIMESTAMP_READLOCK(session, &txn_global->rwlock,
+	    __wt_timestamp_set(
+		&rollback_timestamp, &txn_global->stable_timestamp));
 
 	/*
 	 * Ensure the eviction server is out of the file - we don't
@@ -373,13 +373,10 @@ static int
 __txn_rollback_to_stable_check(WT_SESSION_IMPL *session)
 {
 	WT_TXN_GLOBAL *txn_global;
-	bool stable_set, txn_active;
+	bool txn_active;
 
 	txn_global = &S2C(session)->txn_global;
-	__wt_readlock(session, &txn_global->rwlock);
-	stable_set = !__wt_timestamp_iszero(&txn_global->stable_timestamp);
-	__wt_readunlock(session, &txn_global->rwlock);
-	if (!stable_set)
+	if (!txn_global->has_stable_timestamp)
 		WT_RET_MSG(session, EINVAL,
 		    "rollback_to_stable requires a stable timestamp");
 
diff --git a/src/txn/txn_timestamp.c b/src/txn/txn_timestamp.c
index a947a0167ef..275ef941490 100644
--- a/src/txn/txn_timestamp.c
+++ b/src/txn/txn_timestamp.c
@@ -196,10 +196,9 @@ __txn_global_query_timestamp(
 	if (WT_STRING_MATCH("all_committed", cval.str, cval.len)) {
 		if (!txn_global->has_commit_timestamp)
 			return (WT_NOTFOUND);
-		__wt_readlock(session, &txn_global->rwlock);
-		__wt_timestamp_set(&ts, &txn_global->commit_timestamp);
+		WT_WITH_TIMESTAMP_READLOCK(session, &txn_global->rwlock,
+		    __wt_timestamp_set(&ts, &txn_global->commit_timestamp));
 		WT_ASSERT(session, !__wt_timestamp_iszero(&ts));
-		__wt_readunlock(session, &txn_global->rwlock);
 
 		/* Compare with the oldest running transaction. */
 		__wt_readlock(session, &txn_global->commit_timestamp_rwlock);
@@ -234,9 +233,8 @@ __txn_global_query_timestamp(
 	} else if (WT_STRING_MATCH("stable", cval.str, cval.len)) {
 		if (!txn_global->has_stable_timestamp)
 			return (WT_NOTFOUND);
-		__wt_readlock(session, &txn_global->rwlock);
-		__wt_timestamp_set(&ts, &txn_global->stable_timestamp);
-		__wt_readunlock(session, &txn_global->rwlock);
+		WT_WITH_TIMESTAMP_READLOCK(session, &txn_global->rwlock,
+		    __wt_timestamp_set(&ts, &txn_global->stable_timestamp));
 	} else
 		WT_RET_MSG(session, EINVAL,
 		    "unknown timestamp query %.*s", (int)cval.len, cval.str);
@@ -290,9 +288,9 @@ __wt_txn_update_pinned_timestamp(WT_SESSION_IMPL *session)
 	if (txn_global->oldest_is_pinned)
 		return (0);
 
-	__wt_readlock(session, &txn_global->rwlock);
-	__wt_timestamp_set(&oldest_timestamp, &txn_global->oldest_timestamp);
-	__wt_readunlock(session, &txn_global->rwlock);
+	WT_WITH_TIMESTAMP_READLOCK(session, &txn_global->rwlock,
+	    __wt_timestamp_set(
+		&oldest_timestamp, &txn_global->oldest_timestamp));
 
 	/* Scan to find the global pinned timestamp. */
 	if ((ret = __txn_global_query_timestamp(