WT-2244 Don't wait for transactions after splits.

Now that we split before pages become completely full, and we can block splits
outright with a flag, don't use transaction visibilty to block subsequent
splits.  This had the effect of limiting each page to a single split during
long-running transactions including checkpoints.

7 files changed, 8 insertions, 55 deletions

diff --git a/src/btree/bt_read.c b/src/btree/bt_read.c
index bea6c9cedec..12caf433fd0 100644
--- a/src/btree/bt_read.c
+++ b/src/btree/bt_read.c
@@ -331,7 +331,7 @@ __evict_force_check(WT_SESSION_IMPL *session, WT_REF *ref)
 	__wt_txn_update_oldest(session, false);
 
 	/* If eviction cannot succeed, don't try. */
-	return (__wt_page_can_evict(session, ref, true, NULL));
+	return (__wt_page_can_evict(session, ref, NULL));
 }
 
 /*
diff --git a/src/btree/bt_split.c b/src/btree/bt_split.c
index 3e49d177ca6..d7987f79d41 100644
--- a/src/btree/bt_split.c
+++ b/src/btree/bt_split.c
@@ -409,18 +409,9 @@ __split_ref_move_final(
 	WT_DECL_RET;
 	WT_PAGE *child;
 	WT_REF *ref, *child_ref;
-	uint64_t txn_new_id;
 	uint32_t i;
 
 	/*
-	 * When creating new internal pages as part of a split, we set a field
-	 * in those pages modify structure to prevent them from being evicted
-	 * until all threads are known to have exited the index of the page that
-	 * previously "owned" the WT_REF. Set that field to a safe value.
-	 */
-	txn_new_id = __wt_txn_id_alloc(session, false);
-
-	/*
 	 * The WT_REF structures moved to newly allocated child pages reference
 	 * the wrong parent page and we have to fix that up. The problem is
 	 * revealed when a thread of control searches for the child page's
@@ -471,8 +462,6 @@ __split_ref_move_final(
 			if (child_ref->home != child) {
 				child_ref->home = child;
 				child_ref->pindex_hint = 0;
-
-				child->modify->mod_split_txn = txn_new_id;
 			}
 		} WT_INTL_FOREACH_END;
 		WT_LEAVE_PAGE_INDEX(session);
@@ -1828,13 +1817,6 @@ __split_insert(WT_SESSION_IMPL *session, WT_REF *ref)
 #endif
 
 	/*
-	 * Save the transaction ID when the split happened.  Application
-	 * threads will not try to forcibly evict the page again until
-	 * all concurrent transactions commit.
-	 */
-	page->modify->inmem_split_txn = __wt_txn_id_alloc(session, false);
-
-	/*
 	 * Update the page accounting.
 	 *
 	 * XXX
diff --git a/src/evict/evict_file.c b/src/evict/evict_file.c
index 9937390d19a..2b2117ad9fd 100644
--- a/src/evict/evict_file.c
+++ b/src/evict/evict_file.c
@@ -84,7 +84,7 @@ __wt_evict_file(WT_SESSION_IMPL *session, WT_CACHE_OP syncop)
 			 */
 			WT_ASSERT(session,
 			    F_ISSET(session->dhandle, WT_DHANDLE_DEAD) ||
-			    __wt_page_can_evict(session, ref, false, NULL));
+			    __wt_page_can_evict(session, ref, NULL));
 			__wt_evict_page_clean_update(session, ref, true);
 			break;
 		WT_ILLEGAL_VALUE_ERR(session);
diff --git a/src/evict/evict_lru.c b/src/evict/evict_lru.c
index d7e34e95850..306362de57f 100644
--- a/src/evict/evict_lru.c
+++ b/src/evict/evict_lru.c
@@ -1254,7 +1254,7 @@ __evict_walk_file(WT_SESSION_IMPL *session, u_int *slotp)
 			page->read_gen = __wt_cache_read_gen_new(session);
 
 fast:		/* If the page can't be evicted, give up. */
-		if (!__wt_page_can_evict(session, ref, true, &would_split))
+		if (!__wt_page_can_evict(session, ref, &would_split))
 			continue;
 
 		/*
diff --git a/src/evict/evict_page.c b/src/evict/evict_page.c
index f0d97c7f2c8..26ea9117fae 100644
--- a/src/evict/evict_page.c
+++ b/src/evict/evict_page.c
@@ -434,7 +434,7 @@ __evict_review(
 		if (modified)
 			__wt_txn_update_oldest(session, true);
 
-		if (!__wt_page_can_evict(session, ref, false, inmem_splitp))
+		if (!__wt_page_can_evict(session, ref, inmem_splitp))
 			return (EBUSY);
 
 		/*
diff --git a/src/include/btmem.h b/src/include/btmem.h
index b6c16f36ce5..6ee74c61a38 100644
--- a/src/include/btmem.h
+++ b/src/include/btmem.h
@@ -201,9 +201,6 @@ struct __wt_page_modify {
 	/* The first unwritten transaction ID (approximate). */
 	uint64_t first_dirty_txn;
 
-	/* In-memory split transaction ID. */
-	uint64_t inmem_split_txn;
-
 	/* Avoid checking for obsolete updates during checkpoints. */
 	uint64_t obsolete_check_txn;
 
@@ -303,17 +300,8 @@ struct __wt_page_modify {
 		 * so they can be discarded when no longer needed.
 		 */
 		WT_PAGE *root_split;	/* Linked list of root split pages */
-
-		/*
-		 * When we deepen the tree, newly created internal pages cannot
-		 * be evicted until all threads have exited the original page
-		 * index structure.  We set a transaction value during the split
-		 * that's checked during eviction.
-		 */
-		uint64_t split_txn;	/* Split eviction transaction value */
 	} intl;
 #define	mod_root_split		u2.intl.root_split
-#define	mod_split_txn		u2.intl.split_txn
 	struct {
 		/*
 		 * Appended items to column-stores: there is only a single one
diff --git a/src/include/btree.i b/src/include/btree.i
index 2d2b4e521c5..2e8de5d5535 100644
--- a/src/include/btree.i
+++ b/src/include/btree.i
@@ -1041,13 +1041,11 @@ __wt_page_can_split(WT_SESSION_IMPL *session, WT_PAGE *page)
  *	Check whether a page can be evicted.
  */
 static inline bool
-__wt_page_can_evict(WT_SESSION_IMPL *session,
-    WT_REF *ref, bool check_splits, bool *inmem_splitp)
+__wt_page_can_evict(WT_SESSION_IMPL *session, WT_REF *ref, bool *inmem_splitp)
 {
 	WT_BTREE *btree;
 	WT_PAGE *page;
 	WT_PAGE_MODIFY *mod;
-	WT_TXN_GLOBAL *txn_global;
 
 	if (inmem_splitp != NULL)
 		*inmem_splitp = false;
@@ -1104,25 +1102,10 @@ __wt_page_can_evict(WT_SESSION_IMPL *session,
 	 * a transaction value, we can evict the created page as soon as that
 	 * transaction value is globally visible.
 	 */
-	if (check_splits && WT_PAGE_IS_INTERNAL(page) &&
-	    (F_ISSET_ATOMIC(page, WT_PAGE_SPLIT_BLOCK) ||
-	    !__wt_txn_visible_all(session, mod->mod_split_txn)))
+	if (WT_PAGE_IS_INTERNAL(page) &&
+            F_ISSET_ATOMIC(page, WT_PAGE_SPLIT_BLOCK))
 		return (false);
 
-	/*
-	 * If the page was recently split in-memory, don't evict it immediately:
-	 * we want to give application threads that are appending a chance to
-	 * move to the new leaf page created by the split.
-	 *
-	 * Note the check here is similar to __wt_txn_visible_all, but ignores
-	 * the checkpoint's transaction.
-	 */
-	if (check_splits) {
-		txn_global = &S2C(session)->txn_global;
-		if (WT_TXNID_LE(txn_global->oldest_id, mod->inmem_split_txn))
-			return (false);
-	}
-
 	return (true);
 }
 
@@ -1216,7 +1199,7 @@ __wt_page_release(WT_SESSION_IMPL *session, WT_REF *ref, uint32_t flags)
 	    LF_ISSET(WT_READ_NO_EVICT) ||
 	    F_ISSET(session, WT_SESSION_NO_EVICTION) ||
 	    F_ISSET(btree, WT_BTREE_NO_EVICTION) ||
-	    !__wt_page_can_evict(session, ref, true, NULL))
+	    !__wt_page_can_evict(session, ref, NULL))
 		return (__wt_hazard_clear(session, page));
 
 	WT_RET_BUSY_OK(__wt_page_release_evict(session, ref));