=== modified file 'storage/innobase/ibuf/ibuf0ibuf.c'
--- storage/innobase/ibuf/ibuf0ibuf.c	revid:marko.makela@oracle.com-20100809085837-s1nfx6gjf7l6ttab
+++ storage/innobase/ibuf/ibuf0ibuf.c	2010-08-09 12:52:41 +0000
@@ -2484,7 +2484,6 @@ ibuf_contract_ext(
 	ulint		page_nos[IBUF_MAX_N_PAGES_MERGED];
 	ulint		space_ids[IBUF_MAX_N_PAGES_MERGED];
 	ib_int64_t	space_versions[IBUF_MAX_N_PAGES_MERGED];
-	ulint		n_stored;
 	ulint		sum_sizes;
 	mtr_t		mtr;
 
@@ -2493,7 +2492,7 @@ ibuf_contract_ext(
 
 	mutex_enter(&ibuf_mutex);
 
-	if (ibuf->empty) {
+	if (UNIV_UNLIKELY(ibuf->empty)) {
 		mutex_exit(&ibuf_mutex);
 ibuf_is_empty:
 
@@ -2523,7 +2522,6 @@ ibuf_is_empty:
 	position within the leaf */
 
 	btr_pcur_open_at_rnd_pos(ibuf->index, BTR_SEARCH_LEAF, &pcur, &mtr);
-	mutex_exit(&ibuf_mutex);
 
 	ut_ad(page_validate(btr_pcur_get_page(&pcur), ibuf->index));
 
@@ -2535,6 +2533,7 @@ ibuf_is_empty:
 		in the loop in ibuf_contract_for_n_pages. */
 
 		ibuf->empty = TRUE;
+		mutex_exit(&ibuf_mutex);
 
 		ibuf_exit();
 
@@ -2544,12 +2543,13 @@ ibuf_is_empty:
 		goto ibuf_is_empty;
 	}
 
+	mutex_exit(&ibuf_mutex);
 	sum_sizes = ibuf_get_merge_page_nos(TRUE, btr_pcur_get_rec(&pcur),
 					    space_ids, space_versions,
-					    page_nos, &n_stored);
+					    page_nos, n_pages);
 #if 0 /* defined UNIV_IBUF_DEBUG */
 	fprintf(stderr, "Ibuf contract sync %lu pages %lu volume %lu\n",
-		sync, n_stored, sum_sizes);
+		sync, *n_pages, sum_sizes);
 #endif
 	ibuf_exit();
 
@@ -2557,8 +2557,7 @@ ibuf_is_empty:
 	btr_pcur_close(&pcur);
 
 	buf_read_ibuf_merge_pages(sync, space_ids, space_versions, page_nos,
-				  n_stored);
-	*n_pages = n_stored;
+				  *n_pages);
 
 	return(sum_sizes + 1);
 }
@@ -2628,33 +2627,33 @@ ibuf_contract_after_insert(
 	ibool	sync;
 	ulint	sum_sizes;
 	ulint	size;
+	ulint	max_size;
 
-	mutex_enter(&ibuf_mutex);
-
-	if (ibuf->size < ibuf->max_size + IBUF_CONTRACT_ON_INSERT_NON_SYNC) {
-		mutex_exit(&ibuf_mutex);
+	/* Perform dirty reads of ibuf->size and ibuf->max_size, to
+	reduce ibuf_mutex contention. ibuf->max_size remains constant
+	after ibuf_init_at_db_start(), but ibuf->size should be
+	protected by ibuf_mutex. Given that ibuf->size fits in a
+	machine word, this should be OK; at worst we are doing some
+	excessive ibuf_contract() or occasionally skipping a
+	ibuf_contract(). */
+	size = ibuf->size;
+	max_size = ibuf->max_size;
 
+	if (size < max_size + IBUF_CONTRACT_ON_INSERT_NON_SYNC) {
 		return;
 	}
 
-	sync = FALSE;
-
-	if (ibuf->size >= ibuf->max_size + IBUF_CONTRACT_ON_INSERT_SYNC) {
-
-		sync = TRUE;
-	}
-
-	mutex_exit(&ibuf_mutex);
+	sync = (size >= max_size + IBUF_CONTRACT_ON_INSERT_SYNC);
 
 	/* Contract at least entry_size many bytes */
 	sum_sizes = 0;
 	size = 1;
 
-	while ((size > 0) && (sum_sizes < entry_size)) {
+	do {
 
 		size = ibuf_contract(sync);
 		sum_sizes += size;
-	}
+	} while (size > 0 && sum_sizes < entry_size);
 }
 
 /*********************************************************************//**
@@ -3311,7 +3310,6 @@ ibuf_insert_low(
 	ulint		n_stored;
 	mtr_t		mtr;
 	mtr_t		bitmap_mtr;
-	ibool		too_big;
 
 	ut_a(!dict_index_is_clust(index));
 	ut_ad(dtuple_check_typed(entry));
@@ -3323,11 +3321,14 @@ ibuf_insert_low(
 
 	do_merge = FALSE;
 
-	mutex_enter(&ibuf_mutex);
-	too_big = ibuf->size >= ibuf->max_size + IBUF_CONTRACT_DO_NOT_INSERT;
-	mutex_exit(&ibuf_mutex);
-
-	if (too_big) {
+	/* Perform dirty reads of ibuf->size and ibuf->max_size, to
+	reduce ibuf_mutex contention. ibuf->max_size remains constant
+	after ibuf_init_at_db_start(), but ibuf->size should be
+	protected by ibuf_mutex. Given that ibuf->size fits in a
+	machine word, this should be OK; at worst we are doing some
+	excessive ibuf_contract() or occasionally skipping a
+	ibuf_contract(). */
+	if (ibuf->size >= ibuf->max_size + IBUF_CONTRACT_DO_NOT_INSERT) {
 		/* Insert buffer is now too big, contract it but do not try
 		to insert */
 
@@ -3538,6 +3539,7 @@ bitmap_fail:
 					       thr_get_trx(thr)->id, &mtr);
 		}
 
+		/* The following updates ibuf->empty as well. */
 		ibuf_size_update(root, &mtr);
 	}
 
@@ -3566,14 +3568,14 @@ function_exit:
 	mem_heap_free(heap);
 
 	if (err == DB_SUCCESS) {
-		mutex_enter(&ibuf_mutex);
-
-		ibuf->empty = FALSE;
-
-		mutex_exit(&ibuf_mutex);
-
 		if (mode == BTR_MODIFY_TREE) {
 			ibuf_contract_after_insert(entry_size);
+		} else {
+			/* For BTR_MODIFY_TREE, ibuf->empty was
+			already set in ibuf_size_update(). */
+			mutex_enter(&ibuf_mutex);
+			ibuf->empty = FALSE;
+			mutex_exit(&ibuf_mutex);
 		}
 	}
 
@@ -4108,6 +4110,7 @@ ibuf_delete_rec(
 	if (!ibuf_restore_pos(space, page_no, search_tuple,
 			      BTR_MODIFY_TREE, pcur, mtr)) {
 
+		mutex_exit(&ibuf_mutex);
 		goto func_exit;
 	}
 
@@ -4121,10 +4124,10 @@ ibuf_delete_rec(
 	ibuf_count_set(space, page_no, ibuf_count_get(space, page_no) - 1);
 #endif
 	ibuf_size_update(root, mtr);
+	mutex_exit(&ibuf_mutex);
 	btr_pcur_commit_specify_mtr(pcur, mtr);
 
 func_exit:
-	mutex_exit(&ibuf_mutex);
 	btr_pcur_close(pcur);
 
 	return(TRUE);