WT-2924 Ensure we are doing eviction when threads are waiting for it (#3061)

* Set WT_CACHE_EVICT_XXX when setting WT_CACHE_EVICT_XXX_HARD (the byte count checks can race, so we have to explicitly set both).

* Make  WT_CACHE.pages_evict volatile: loops in __evict_pass() and __wt_cache_eviction_worker() read the value and depend on it being updated when subsequently read.

3 files changed, 18 insertions, 17 deletions

diff --git a/src/evict/evict_lru.c b/src/evict/evict_lru.c
index fcea343c2a1..3be7a124a1d 100644
--- a/src/evict/evict_lru.c
+++ b/src/evict/evict_lru.c
@@ -456,13 +456,13 @@ __evict_update_work(WT_SESSION_IMPL *session)
 	if (bytes_inuse > (cache->eviction_target * bytes_max) / 100)
 		F_SET(cache, WT_CACHE_EVICT_CLEAN);
 	if (__wt_eviction_clean_needed(session, NULL))
-		F_SET(cache, WT_CACHE_EVICT_CLEAN_HARD);
+		F_SET(cache, WT_CACHE_EVICT_CLEAN | WT_CACHE_EVICT_CLEAN_HARD);
 
 	dirty_inuse = __wt_cache_dirty_leaf_inuse(cache);
 	if (dirty_inuse > (cache->eviction_dirty_target * bytes_max) / 100)
 		F_SET(cache, WT_CACHE_EVICT_DIRTY);
 	if (__wt_eviction_dirty_needed(session, NULL))
-		F_SET(cache, WT_CACHE_EVICT_DIRTY_HARD);
+		F_SET(cache, WT_CACHE_EVICT_DIRTY | WT_CACHE_EVICT_DIRTY_HARD);
 
 	/*
 	 * If application threads are blocked by the total volume of data in
@@ -1774,22 +1774,9 @@ __wt_cache_eviction_worker(WT_SESSION_IMPL *session, bool busy, u_int pct_full)
 	/* Wake the eviction server if we need to do work. */
 	__wt_evict_server_wake(session);
 
-	/*
-	 * If we're busy, either because of the transaction check we just did,
-	 * or because our caller is waiting on a longer-than-usual event (such
-	 * as a page read), limit the work to a single eviction and return. If
-	 * that's not the case, we can do more.
-	 */
 	init_evict_count = cache->pages_evict;
 
 	for (;;) {
-		/* Check if we have become busy. */
-		if (!busy && txn_state->snap_min != WT_TXN_NONE &&
-		    txn_global->current != txn_global->oldest_id)
-			busy = true;
-
-		max_pages_evicted = busy ? 5 : 20;
-
 		/*
 		 * A pathological case: if we're the oldest transaction in the
 		 * system and the eviction server is stuck trying to find space,
@@ -1802,6 +1789,20 @@ __wt_cache_eviction_worker(WT_SESSION_IMPL *session, bool busy, u_int pct_full)
 			return (WT_ROLLBACK);
 		}
 
+		/*
+		 * Check if we have become busy.
+		 *
+		 * If we're busy (because of the transaction check we just did
+		 * or because our caller is waiting on a longer-than-usual event
+		 * such as a page read), and the cache level drops below 100%,
+		 * limit the work to 5 evictions and return. If that's not the
+		 * case, we can do more.
+		 */
+		if (!busy && txn_state->snap_min != WT_TXN_NONE &&
+		    txn_global->current != txn_global->oldest_id)
+			busy = true;
+		max_pages_evicted = busy ? 5 : 20;
+
 		/* See if eviction is still needed. */
 		if (!__wt_eviction_needed(session, busy, &pct_full) ||
 		    (pct_full < 100 &&
diff --git a/src/include/btree.i b/src/include/btree.i
index 6e32c1bc195..a9ce4f754a9 100644
--- a/src/include/btree.i
+++ b/src/include/btree.i
@@ -406,7 +406,7 @@ __wt_cache_page_evict(WT_SESSION_IMPL *session, WT_PAGE *page)
 
 	/* Update pages and bytes evicted. */
 	(void)__wt_atomic_add64(&cache->bytes_evict, page->memory_footprint);
-	(void)__wt_atomic_add64(&cache->pages_evict, 1);
+	(void)__wt_atomic_addv64(&cache->pages_evict, 1);
 }
 
 /*
diff --git a/src/include/cache.h b/src/include/cache.h
index fceba6536c2..b24b625aec4 100644
--- a/src/include/cache.h
+++ b/src/include/cache.h
@@ -66,7 +66,7 @@ struct __wt_cache {
 	uint64_t bytes_dirty_leaf;
 	uint64_t pages_dirty_leaf;
 	uint64_t bytes_evict;		/* Bytes/pages discarded by eviction */
-	uint64_t pages_evict;
+	volatile uint64_t pages_evict;
 	uint64_t pages_evicted;		/* Pages evicted during a pass */
 	uint64_t bytes_image;		/* Bytes of disk images */
 	uint64_t bytes_inmem;		/* Bytes/pages in memory */