MDEV-12534 Use atomic operations whenever available

Allow 64-bit atomic operations on 32-bit systems,
only relying on HAVE_ATOMIC_BUILTINS_64, disregarding
the width of the register file.

Define UNIV_WORD_SIZE correctly on all systems, including Windows.
In MariaDB 10.0 and 10.1, it was incorrectly defined as 4 on
64-bit Windows.

Define HAVE_ATOMIC_BUILTINS_64 on Windows
(64-bit atomics are available on both 32-bit and 64-bit Windows
platforms; the operations were unnecessarily disabled even on
64-bit Windows).

MONITOR_OS_PENDING_READS, MONITOR_OS_PENDING_WRITES: Enable by default.

os_file_n_pending_preads, os_file_n_pending_pwrites,
os_n_pending_reads, os_n_pending_writes: Remove.
Use the monitor counters instead.

os_file_count_mutex: Remove. On a system that does not support
64-bit atomics, monitor_mutex will be used instead.

18 files changed, 216 insertions, 407 deletions

diff --git a/storage/innobase/buf/buf0rea.cc b/storage/innobase/buf/buf0rea.cc
index 7c8369c0c09..27f45308813 100644
--- a/storage/innobase/buf/buf0rea.cc
+++ b/storage/innobase/buf/buf0rea.cc
@@ -881,15 +881,11 @@ buf_read_recv_pages(
 			count++;
 
 			if (count > 1000) {
-				fprintf(stderr,
-					"InnoDB: Error: InnoDB has waited for"
-					" 10 seconds for pending\n"
-					"InnoDB: reads to the buffer pool to"
-					" be finished.\n"
-					"InnoDB: Number of pending reads %lu,"
-					" pending pread calls %lu\n",
-					(ulong) buf_pool->n_pend_reads,
-					(ulong) os_file_n_pending_preads);
+				ib_logf(IB_LOG_LEVEL_ERROR,
+					"waited for 10 seconds for " ULINTPF
+					" pending reads to the buffer pool to"
+					" be finished",
+					buf_pool->n_pend_reads);
 
 				os_aio_print_debug = TRUE;
 			}
diff --git a/storage/innobase/include/os0file.h b/storage/innobase/include/os0file.h
index 6cb4f54d629..bdb4682eafb 100644
--- a/storage/innobase/include/os0file.h
+++ b/storage/innobase/include/os0file.h
@@ -2,7 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2009, Percona Inc.
-Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
+Copyright (c) 2013, 2017, MariaDB Corporation.
 
 Portions of this file contain modifications contributed and copyrighted
 by Percona Inc.. Those modifications are
@@ -51,16 +51,6 @@ extern ibool	os_has_said_disk_full;
 /** Flag: enable debug printout for asynchronous i/o */
 extern ibool	os_aio_print_debug;
 
-/** Number of pending os_file_pread() operations */
-extern ulint	os_file_n_pending_preads;
-/** Number of pending os_file_pwrite() operations */
-extern ulint	os_file_n_pending_pwrites;
-
-/** Number of pending read operations */
-extern ulint	os_n_pending_reads;
-/** Number of pending write operations */
-extern ulint	os_n_pending_writes;
-
 #ifdef __WIN__
 
 /** We define always WIN_ASYNC_IO, and check at run-time whether
diff --git a/storage/innobase/include/os0sync.h b/storage/innobase/include/os0sync.h
index 0754210c47a..dd6de43dc0b 100644
--- a/storage/innobase/include/os0sync.h
+++ b/storage/innobase/include/os0sync.h
@@ -667,10 +667,7 @@ os_atomic_clear(volatile lock_word_t* ptr)
 
 # define HAVE_ATOMIC_BUILTINS
 # define HAVE_ATOMIC_BUILTINS_BYTE
-
-# ifndef _WIN32
-#  define HAVE_ATOMIC_BUILTINS_64
-# endif
+# define HAVE_ATOMIC_BUILTINS_64
 
 /**********************************************************//**
 Atomic compare and exchange of signed integers (both 32 and 64 bit).
diff --git a/storage/innobase/include/srv0mon.h b/storage/innobase/include/srv0mon.h
index 2d90f47eefe..09af5d4159b 100644
--- a/storage/innobase/include/srv0mon.h
+++ b/storage/innobase/include/srv0mon.h
@@ -2,6 +2,7 @@
 
 Copyright (c) 2010, 2013, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
+Copyright (c) 2017, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it
 under the terms of the GNU General Public License as published by the
@@ -541,22 +542,30 @@ on the counters */
 
 /** Increment a monitor counter under mutex protection.
 Use MONITOR_INC if appropriate mutex protection already exists.
+@param mutex	mutex to acquire and release
 @param monitor	monitor to be incremented by 1
-@param mutex	mutex to acquire and relese */
-# define MONITOR_MUTEX_INC(mutex, monitor)				\
+@param enabled	whether the monitor is enabled */
+#define MONITOR_MUTEX_INC_LOW(mutex, monitor, enabled)			\
 	ut_ad(!mutex_own(mutex));					\
-	if (MONITOR_IS_ON(monitor)) {					\
+	if (enabled) {							\
 		mutex_enter(mutex);					\
 		if (++MONITOR_VALUE(monitor) > MONITOR_MAX_VALUE(monitor)) { \
 			MONITOR_MAX_VALUE(monitor) = MONITOR_VALUE(monitor); \
 		}							\
 		mutex_exit(mutex);					\
 	}
+/** Increment a monitor counter under mutex protection.
+Use MONITOR_INC if appropriate mutex protection already exists.
+@param mutex	mutex to acquire and release
+@param monitor	monitor to be incremented by 1 */
+#define MONITOR_MUTEX_INC(mutex, monitor)				\
+	MONITOR_MUTEX_INC_LOW(mutex, monitor, MONITOR_IS_ON(monitor))
 /** Decrement a monitor counter under mutex protection.
 Use MONITOR_DEC if appropriate mutex protection already exists.
+@param mutex	mutex to acquire and release
 @param monitor	monitor to be decremented by 1
-@param mutex	mutex to acquire and relese */
-# define MONITOR_MUTEX_DEC(mutex, monitor)				\
+@param enabled	whether the monitor is enabled */
+#define MONITOR_MUTEX_DEC_LOW(mutex, monitor, enabled)			\
 	ut_ad(!mutex_own(mutex));					\
 	if (MONITOR_IS_ON(monitor)) {					\
 		mutex_enter(mutex);					\
@@ -565,13 +574,20 @@ Use MONITOR_DEC if appropriate mutex protection already exists.
 		}							\
 		mutex_exit(mutex);					\
 	}
+/** Decrement a monitor counter under mutex protection.
+Use MONITOR_DEC if appropriate mutex protection already exists.
+@param mutex	mutex to acquire and release
+@param monitor	monitor to be decremented by 1 */
+#define MONITOR_MUTEX_DEC(mutex, monitor)				\
+	MONITOR_MUTEX_DEC_LOW(mutex, monitor, MONITOR_IS_ON(monitor))
 
 #if defined HAVE_ATOMIC_BUILTINS_64
 /** Atomically increment a monitor counter.
 Use MONITOR_INC if appropriate mutex protection exists.
-@param monitor	monitor to be incremented by 1 */
-# define MONITOR_ATOMIC_INC(monitor)					\
-	if (MONITOR_IS_ON(monitor)) {					\
+@param monitor	monitor to be incremented by 1
+@param enabled	whether the monitor is enabled */
+# define MONITOR_ATOMIC_INC_LOW(monitor, enabled)			\
+	if (enabled) {					\
 		ib_uint64_t	value;					\
 		value  = os_atomic_increment_uint64(			\
 			(ib_uint64_t*) &MONITOR_VALUE(monitor),	 1);	\
@@ -584,9 +600,10 @@ Use MONITOR_INC if appropriate mutex protection exists.
 
 /** Atomically decrement a monitor counter.
 Use MONITOR_DEC if appropriate mutex protection exists.
-@param monitor	monitor to be decremented by 1 */
-# define MONITOR_ATOMIC_DEC(monitor)					\
-	if (MONITOR_IS_ON(monitor)) {					\
+@param monitor	monitor to be decremented by 1
+@param enabled	whether the monitor is enabled */
+# define MONITOR_ATOMIC_DEC_LOW(monitor, enabled)			\
+	if (enabled) {							\
 		ib_uint64_t	value;					\
 		value = os_atomic_decrement_uint64(			\
 			(ib_uint64_t*) &MONITOR_VALUE(monitor), 1);	\
@@ -617,14 +634,29 @@ srv_mon_free(void);
 
 /** Atomically increment a monitor counter.
 Use MONITOR_INC if appropriate mutex protection exists.
-@param monitor	monitor to be incremented by 1 */
-# define MONITOR_ATOMIC_INC(monitor) MONITOR_MUTEX_INC(&monitor_mutex, monitor)
+@param monitor	monitor to be incremented by 1
+@param enabled	whether the monitor is enabled */
+# define MONITOR_ATOMIC_INC_LOW(monitor, enabled)		\
+	MONITOR_MUTEX_INC_LOW(&monitor_mutex, monitor, enabled)
 /** Atomically decrement a monitor counter.
 Use MONITOR_DEC if appropriate mutex protection exists.
-@param monitor	monitor to be decremented by 1 */
-# define MONITOR_ATOMIC_DEC(monitor) MONITOR_MUTEX_DEC(&monitor_mutex, monitor)
+@param monitor	monitor to be decremented by 1
+@param enabled	whether the monitor is enabled */
+# define MONITOR_ATOMIC_DEC_LOW(monitor, enabled)		\
+	MONITOR_MUTEX_DEC_LOW(&monitor_mutex, monitor, enabled)
 #endif /* HAVE_ATOMIC_BUILTINS_64 */
 
+/** Atomically increment a monitor counter if it is enabled.
+Use MONITOR_INC if appropriate mutex protection exists.
+@param monitor	monitor to be incremented by 1 */
+#define MONITOR_ATOMIC_INC(monitor)				\
+	MONITOR_ATOMIC_INC_LOW(monitor, MONITOR_IS_ON(monitor))
+/** Atomically decrement a monitor counter if it is enabled.
+Use MONITOR_DEC if appropriate mutex protection exists.
+@param monitor	monitor to be decremented by 1 */
+#define MONITOR_ATOMIC_DEC(monitor)				\
+	MONITOR_ATOMIC_DEC_LOW(monitor, MONITOR_IS_ON(monitor))
+
 #define	MONITOR_DEC(monitor)						\
 	if (MONITOR_IS_ON(monitor)) {					\
 		MONITOR_VALUE(monitor)--;				\
diff --git a/storage/innobase/include/univ.i b/storage/innobase/include/univ.i
index 824a06829f9..fc0bf0aeeca 100644
--- a/storage/innobase/include/univ.i
+++ b/storage/innobase/include/univ.i
@@ -285,22 +285,12 @@ definitions: */
 
 #endif /* !UNIV_MUST_NOT_INLINE */
 
-#ifdef _WIN32
-#define UNIV_WORD_SIZE		4
-#elif defined(_WIN64)
-#define UNIV_WORD_SIZE		8
-#else
-/** MySQL config.h generated by GNU autoconf will define SIZEOF_LONG in Posix */
-#define UNIV_WORD_SIZE		SIZEOF_LONG
-#endif
+#define UNIV_WORD_SIZE		SIZEOF_SIZE_T
 
 /** The following alignment is used in memory allocations in memory heap
 management to ensure correct alignment for doubles etc. */
 #define UNIV_MEM_ALIGNMENT	8
 
-/** The following alignment is used in aligning lints etc. */
-#define UNIV_WORD_ALIGNMENT	UNIV_WORD_SIZE
-
 /*
 			DATABASE VERSION CONTROL
 			========================
diff --git a/storage/innobase/os/os0file.cc b/storage/innobase/os/os0file.cc
index eb8b3a53d32..ff67c90eecf 100644
--- a/storage/innobase/os/os0file.cc
+++ b/storage/innobase/os/os0file.cc
@@ -2,7 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2009, Percona Inc.
-Copyright (c) 2012, 2017, MariaDB Corporation. All Rights Reserved.
+Copyright (c) 2013, 2017, MariaDB Corporation.
 
 Portions of this file contain modifications contributed and copyrighted
 by Percona Inc.. Those modifications are
@@ -284,21 +284,6 @@ UNIV_INTERN time_t	os_last_printout;
 
 UNIV_INTERN ibool	os_has_said_disk_full	= FALSE;
 
-#if !defined(UNIV_HOTBACKUP)	\
-    && (!defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8)
-/** The mutex protecting the following counts of pending I/O operations */
-static os_ib_mutex_t	os_file_count_mutex;
-#endif /* !UNIV_HOTBACKUP && (!HAVE_ATOMIC_BUILTINS || UNIV_WORD_SIZE < 8) */
-
-/** Number of pending os_file_pread() operations */
-UNIV_INTERN ulint	os_file_n_pending_preads  = 0;
-/** Number of pending os_file_pwrite() operations */
-UNIV_INTERN ulint	os_file_n_pending_pwrites = 0;
-/** Number of pending write operations */
-UNIV_INTERN ulint	os_n_pending_writes = 0;
-/** Number of pending read operations */
-UNIV_INTERN ulint	os_n_pending_reads = 0;
-
 #ifdef UNIV_DEBUG
 # ifndef UNIV_HOTBACKUP
 /**********************************************************************//**
@@ -752,10 +737,6 @@ void
 os_io_init_simple(void)
 /*===================*/
 {
-#if !defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8
-	os_file_count_mutex = os_mutex_create();
-#endif /* !HAVE_ATOMIC_BUILTINS || UNIV_WORD_SIZE < 8 */
-
 	for (ulint i = 0; i < OS_FILE_N_SEEK_MUTEXES; i++) {
 		os_file_seek_mutexes[i] = os_mutex_create();
 	}
@@ -2364,9 +2345,6 @@ os_file_pread(
 	os_offset_t	offset)	/*!< in: file offset from where to read */
 {
 	off_t	offs;
-#if defined(HAVE_PREAD) && !defined(HAVE_BROKEN_PREAD)
-	ssize_t	n_bytes;
-#endif /* HAVE_PREAD && !HAVE_BROKEN_PREAD */
 
 	ut_ad(n);
 
@@ -2383,33 +2361,12 @@ os_file_pread(
 
 	os_n_file_reads++;
 
-#if defined(HAVE_PREAD) && !defined(HAVE_BROKEN_PREAD)
-#if defined(HAVE_ATOMIC_BUILTINS) && UNIV_WORD_SIZE == 8
-	(void) os_atomic_increment_ulint(&os_n_pending_reads, 1);
-	(void) os_atomic_increment_ulint(&os_file_n_pending_preads, 1);
-	MONITOR_ATOMIC_INC(MONITOR_OS_PENDING_READS);
-#else
-	os_mutex_enter(os_file_count_mutex);
-	os_file_n_pending_preads++;
-	os_n_pending_reads++;
-	MONITOR_INC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
-#endif /* HAVE_ATOMIC_BUILTINS && UNIV_WORD == 8 */
-
-	n_bytes = pread(file, buf, n, offs);
-
-#if defined(HAVE_ATOMIC_BUILTINS) && UNIV_WORD_SIZE == 8
-	(void) os_atomic_decrement_ulint(&os_n_pending_reads, 1);
-	(void) os_atomic_decrement_ulint(&os_file_n_pending_preads, 1);
-	MONITOR_ATOMIC_DEC(MONITOR_OS_PENDING_READS);
-#else
-	os_mutex_enter(os_file_count_mutex);
-	os_file_n_pending_preads--;
-	os_n_pending_reads--;
-	MONITOR_DEC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
-#endif /* !HAVE_ATOMIC_BUILTINS || UNIV_WORD == 8 */
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_READS);
 
+#ifdef HAVE_PREAD
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_READS, monitor);
+	ssize_t n_bytes = pread(file, buf, n, offs);
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 	return(n_bytes);
 #else
 	{
@@ -2419,15 +2376,7 @@ os_file_pread(
 		ulint	i;
 #endif /* !UNIV_HOTBACKUP */
 
-#if defined(HAVE_ATOMIC_BUILTINS) && UNIV_WORD_SIZE == 8
-		(void) os_atomic_increment_ulint(&os_n_pending_reads, 1);
-		MONITOR_ATOMIC_INC(MONITOR_OS_PENDING_READS);
-#else
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_reads++;
-		MONITOR_INC(MONITOR_OS_PENDING_READS);
-		os_mutex_exit(os_file_count_mutex);
-#endif /* HAVE_ATOMIC_BUILTINS && UNIV_WORD == 8 */
+		MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_READS, monitor);
 #ifndef UNIV_HOTBACKUP
 		/* Protect the seek / read operation with a mutex */
 		i = ((ulint) file) % OS_FILE_N_SEEK_MUTEXES;
@@ -2447,16 +2396,7 @@ os_file_pread(
 		os_mutex_exit(os_file_seek_mutexes[i]);
 #endif /* !UNIV_HOTBACKUP */
 
-#if defined(HAVE_ATOMIC_BUILTINS) && UNIV_WORD_SIZE == 8
-		(void) os_atomic_decrement_ulint(&os_n_pending_reads, 1);
-		MONITOR_ATOIC_DEC(MONITOR_OS_PENDING_READS);
-#else
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_reads--;
-		MONITOR_DEC(MONITOR_OS_PENDING_READS);
-		os_mutex_exit(os_file_count_mutex);
-#endif /* HAVE_ATOMIC_BUILTINS && UNIV_WORD_SIZE == 8 */
-
+		MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 		return(ret);
 	}
 #endif
@@ -2493,32 +2433,11 @@ os_file_pwrite(
 
 	os_n_file_writes++;
 
-#if defined(HAVE_PWRITE) && !defined(HAVE_BROKEN_PREAD)
-#if !defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8
-	os_mutex_enter(os_file_count_mutex);
-	os_file_n_pending_pwrites++;
-	os_n_pending_writes++;
-	MONITOR_INC(MONITOR_OS_PENDING_WRITES);
-	os_mutex_exit(os_file_count_mutex);
-#else
-	(void) os_atomic_increment_ulint(&os_n_pending_writes, 1);
-	(void) os_atomic_increment_ulint(&os_file_n_pending_pwrites, 1);
-	MONITOR_ATOMIC_INC(MONITOR_OS_PENDING_WRITES);
-#endif /* !HAVE_ATOMIC_BUILTINS || UNIV_WORD < 8 */
-
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_WRITES);
+#ifdef HAVE_PWRITE
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 	ret = pwrite(file, buf, (ssize_t) n, offs);
-
-#if !defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8
-	os_mutex_enter(os_file_count_mutex);
-	os_file_n_pending_pwrites--;
-	os_n_pending_writes--;
-	MONITOR_DEC(MONITOR_OS_PENDING_WRITES);
-	os_mutex_exit(os_file_count_mutex);
-#else
-	(void) os_atomic_decrement_ulint(&os_n_pending_writes, 1);
-	(void) os_atomic_decrement_ulint(&os_file_n_pending_pwrites, 1);
-	MONITOR_ATOMIC_DEC(MONITOR_OS_PENDING_WRITES);
-#endif /* !HAVE_ATOMIC_BUILTINS || UNIV_WORD < 8 */
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 	return(ret);
 #else
@@ -2528,10 +2447,7 @@ os_file_pwrite(
 		ulint	i;
 # endif /* !UNIV_HOTBACKUP */
 
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_writes++;
-		MONITOR_INC(MONITOR_OS_PENDING_WRITES);
-		os_mutex_exit(os_file_count_mutex);
+		MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 # ifndef UNIV_HOTBACKUP
 		/* Protect the seek / write operation with a mutex */
@@ -2555,14 +2471,10 @@ func_exit:
 		os_mutex_exit(os_file_seek_mutexes[i]);
 # endif /* !UNIV_HOTBACKUP */
 
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_writes--;
-		MONITOR_DEC(MONITOR_OS_PENDING_WRITES);
-		os_mutex_exit(os_file_count_mutex);
-
+		MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 		return(ret);
 	}
-#endif /* !UNIV_HOTBACKUP */
+#endif /* HAVE_PWRITE */
 }
 #endif
 
@@ -2597,6 +2509,7 @@ os_file_read_func(
 
 	os_n_file_reads++;
 	os_bytes_read_since_printout += n;
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_READS);
 
 try_again:
 	ut_ad(buf);
@@ -2605,10 +2518,7 @@ try_again:
 	low = (DWORD) offset & 0xFFFFFFFF;
 	high = (DWORD) (offset >> 32);
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_reads++;
-	MONITOR_INC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 #ifndef UNIV_HOTBACKUP
 	/* Protect the seek / read operation with a mutex */
@@ -2626,11 +2536,7 @@ try_again:
 		os_mutex_exit(os_file_seek_mutexes[i]);
 #endif /* !UNIV_HOTBACKUP */
 
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_reads--;
-		MONITOR_DEC(MONITOR_OS_PENDING_READS);
-		os_mutex_exit(os_file_count_mutex);
-
+		MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 		goto error_handling;
 	}
 
@@ -2640,10 +2546,7 @@ try_again:
 	os_mutex_exit(os_file_seek_mutexes[i]);
 #endif /* !UNIV_HOTBACKUP */
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_reads--;
-	MONITOR_DEC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 	if (ret && len == n) {
 		return(TRUE);
@@ -2728,6 +2631,7 @@ os_file_read_no_error_handling_func(
 
 	os_n_file_reads++;
 	os_bytes_read_since_printout += n;
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_READS);
 
 try_again:
 	ut_ad(buf);
@@ -2736,10 +2640,7 @@ try_again:
 	low = (DWORD) offset & 0xFFFFFFFF;
 	high = (DWORD) (offset >> 32);
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_reads++;
-	MONITOR_INC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 #ifndef UNIV_HOTBACKUP
 	/* Protect the seek / read operation with a mutex */
@@ -2757,11 +2658,7 @@ try_again:
 		os_mutex_exit(os_file_seek_mutexes[i]);
 #endif /* !UNIV_HOTBACKUP */
 
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_reads--;
-		MONITOR_DEC(MONITOR_OS_PENDING_READS);
-		os_mutex_exit(os_file_count_mutex);
-
+		MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 		goto error_handling;
 	}
 
@@ -2771,10 +2668,7 @@ try_again:
 	os_mutex_exit(os_file_seek_mutexes[i]);
 #endif /* !UNIV_HOTBACKUP */
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_reads--;
-	MONITOR_DEC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 	if (ret && len == n) {
 		return(TRUE);
@@ -2854,7 +2748,6 @@ os_file_write_func(
 	ulint		n)	/*!< in: number of bytes to write */
 {
 	ut_ad(!srv_read_only_mode);
-
 #ifdef __WIN__
 	BOOL		ret;
 	DWORD		len;
@@ -2876,14 +2769,12 @@ os_file_write_func(
 
 	ut_ad(buf);
 	ut_ad(n > 0);
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_WRITES);
 retry:
 	low = (DWORD) offset & 0xFFFFFFFF;
 	high = (DWORD) (offset >> 32);
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_writes++;
-	MONITOR_INC(MONITOR_OS_PENDING_WRITES);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 #ifndef UNIV_HOTBACKUP
 	/* Protect the seek / write operation with a mutex */
@@ -2901,10 +2792,7 @@ retry:
 		os_mutex_exit(os_file_seek_mutexes[i]);
 #endif /* !UNIV_HOTBACKUP */
 
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_writes--;
-		MONITOR_DEC(MONITOR_OS_PENDING_WRITES);
-		os_mutex_exit(os_file_count_mutex);
+		MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 		ut_print_timestamp(stderr);
 
@@ -2928,10 +2816,7 @@ retry:
 	os_mutex_exit(os_file_seek_mutexes[i]);
 #endif /* !UNIV_HOTBACKUP */
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_writes--;
-	MONITOR_DEC(MONITOR_OS_PENDING_WRITES);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 	if (ret && len == n) {
 
@@ -5751,19 +5636,24 @@ os_aio_print(
 	time_elapsed = 0.001 + difftime(current_time, os_last_printout);
 
 	fprintf(file,
-		"Pending flushes (fsync) log: %lu; buffer pool: %lu\n"
-		"%lu OS file reads, %lu OS file writes, %lu OS fsyncs\n",
-		(ulong) fil_n_pending_log_flushes,
-		(ulong) fil_n_pending_tablespace_flushes,
-		(ulong) os_n_file_reads,
-		(ulong) os_n_file_writes,
-		(ulong) os_n_fsyncs);
-
-	if (os_file_n_pending_preads != 0 || os_file_n_pending_pwrites != 0) {
+		"Pending flushes (fsync) log: " ULINTPF
+		"; buffer pool: " ULINTPF "\n"
+		ULINTPF " OS file reads, "
+		ULINTPF " OS file writes, "
+		ULINTPF " OS fsyncs\n",
+		fil_n_pending_log_flushes,
+		fil_n_pending_tablespace_flushes,
+		os_n_file_reads,
+		os_n_file_writes,
+		os_n_fsyncs);
+
+	const ulint n_reads = MONITOR_VALUE(MONITOR_OS_PENDING_READS);
+	const ulint n_writes = MONITOR_VALUE(MONITOR_OS_PENDING_WRITES);
+
+	if (n_reads != 0 || n_writes != 0) {
 		fprintf(file,
-			"%lu pending preads, %lu pending pwrites\n",
-			(ulong) os_file_n_pending_preads,
-			(ulong) os_file_n_pending_pwrites);
+			ULINTPF " pending reads, " ULINTPF " pending writes\n",
+			n_reads, n_writes);
 	}
 
 	if (os_n_file_reads == os_n_file_reads_old) {
diff --git a/storage/innobase/srv/srv0mon.cc b/storage/innobase/srv/srv0mon.cc
index 4a709160ea6..ea21a4c1454 100644
--- a/storage/innobase/srv/srv0mon.cc
+++ b/storage/innobase/srv/srv0mon.cc
@@ -2,6 +2,7 @@
 
 Copyright (c) 2010, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
+Copyright (c) 2017, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -643,11 +644,11 @@ static monitor_info_t	innodb_counter_info[] =
 	 MONITOR_DEFAULT_START, MONITOR_OVLD_OS_FSYNC},
 
 	{"os_pending_reads", "os", "Number of reads pending",
-	 MONITOR_NONE,
+	 MONITOR_DEFAULT_ON,
 	 MONITOR_DEFAULT_START, MONITOR_OS_PENDING_READS},
 
 	{"os_pending_writes", "os", "Number of writes pending",
-	 MONITOR_NONE,
+	 MONITOR_DEFAULT_ON,
 	 MONITOR_DEFAULT_START, MONITOR_OS_PENDING_WRITES},
 
 	{"os_log_bytes_written", "os",
diff --git a/storage/innobase/srv/srv0srv.cc b/storage/innobase/srv/srv0srv.cc
index 723ae838f07..58e69c3c9e7 100644
--- a/storage/innobase/srv/srv0srv.cc
+++ b/storage/innobase/srv/srv0srv.cc
@@ -1409,10 +1409,10 @@ srv_export_innodb_status(void)
 	mutex_enter(&srv_innodb_monitor_mutex);
 
 	export_vars.innodb_data_pending_reads =
-		os_n_pending_reads;
+		MONITOR_VALUE(MONITOR_OS_PENDING_READS);
 
 	export_vars.innodb_data_pending_writes =
-		os_n_pending_writes;
+		MONITOR_VALUE(MONITOR_OS_PENDING_WRITES);
 
 	export_vars.innodb_data_pending_fsyncs =
 		fil_n_pending_log_flushes
diff --git a/storage/innobase/sync/sync0arr.cc b/storage/innobase/sync/sync0arr.cc
index c7163695a3f..6ffe3cab8c8 100644
--- a/storage/innobase/sync/sync0arr.cc
+++ b/storage/innobase/sync/sync0arr.cc
@@ -1069,9 +1069,10 @@ sync_array_print_long_waits(
 		now the values of pending calls of these. */
 
 		fprintf(stderr,
-			"InnoDB: Pending preads %lu, pwrites %lu\n",
-			(ulong) os_file_n_pending_preads,
-			(ulong) os_file_n_pending_pwrites);
+			"InnoDB: Pending reads " UINT64PF
+			", writes " UINT64PF "\n",
+			MONITOR_VALUE(MONITOR_OS_PENDING_READS),
+			MONITOR_VALUE(MONITOR_OS_PENDING_WRITES));
 
 		srv_print_innodb_monitor = TRUE;
 		os_event_set(srv_monitor_event);
diff --git a/storage/xtradb/buf/buf0rea.cc b/storage/xtradb/buf/buf0rea.cc
index c28df72df92..9053f38924e 100644
--- a/storage/xtradb/buf/buf0rea.cc
+++ b/storage/xtradb/buf/buf0rea.cc
@@ -986,15 +986,11 @@ not_to_recover:
 			count++;
 
 			if (count > 1000) {
-				fprintf(stderr,
-					"InnoDB: Error: InnoDB has waited for"
-					" 10 seconds for pending\n"
-					"InnoDB: reads to the buffer pool to"
-					" be finished.\n"
-					"InnoDB: Number of pending reads %lu,"
-					" pending pread calls %lu\n",
-					(ulong) buf_pool->n_pend_reads,
-					(ulong) os_file_n_pending_preads);
+				ib_logf(IB_LOG_LEVEL_ERROR,
+					"waited for 10 seconds for " ULINTPF
+					" pending reads to the buffer pool to"
+					" be finished",
+					buf_pool->n_pend_reads);
 
 				os_aio_print_debug = TRUE;
 			}
diff --git a/storage/xtradb/include/os0file.h b/storage/xtradb/include/os0file.h
index 60a9c3475e7..b8f30977fbe 100644
--- a/storage/xtradb/include/os0file.h
+++ b/storage/xtradb/include/os0file.h
@@ -2,7 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2009, Percona Inc.
-Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
+Copyright (c) 2013, 2017, MariaDB Corporation.
 
 Portions of this file contain modifications contributed and copyrighted
 by Percona Inc.. Those modifications are
@@ -52,16 +52,6 @@ extern ibool	os_has_said_disk_full;
 /** Flag: enable debug printout for asynchronous i/o */
 extern ibool	os_aio_print_debug;
 
-/** Number of pending os_file_pread() operations */
-extern ulint	os_file_n_pending_preads;
-/** Number of pending os_file_pwrite() operations */
-extern ulint	os_file_n_pending_pwrites;
-
-/** Number of pending read operations */
-extern ulint	os_n_pending_reads;
-/** Number of pending write operations */
-extern ulint	os_n_pending_writes;
-
 #ifdef __WIN__
 
 /** We define always WIN_ASYNC_IO, and check at run-time whether
diff --git a/storage/xtradb/include/os0sync.h b/storage/xtradb/include/os0sync.h
index f6207555f1a..48c56a73369 100644
--- a/storage/xtradb/include/os0sync.h
+++ b/storage/xtradb/include/os0sync.h
@@ -718,10 +718,7 @@ os_atomic_clear(volatile lock_word_t* ptr)
 
 # define HAVE_ATOMIC_BUILTINS
 # define HAVE_ATOMIC_BUILTINS_BYTE
-
-# ifndef _WIN32
-#  define HAVE_ATOMIC_BUILTINS_64
-# endif
+# define HAVE_ATOMIC_BUILTINS_64
 
 /**********************************************************//**
 Atomic compare and exchange of signed integers (both 32 and 64 bit).
diff --git a/storage/xtradb/include/srv0mon.h b/storage/xtradb/include/srv0mon.h
index 2d90f47eefe..09af5d4159b 100644
--- a/storage/xtradb/include/srv0mon.h
+++ b/storage/xtradb/include/srv0mon.h
@@ -2,6 +2,7 @@
 
 Copyright (c) 2010, 2013, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
+Copyright (c) 2017, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it
 under the terms of the GNU General Public License as published by the
@@ -541,22 +542,30 @@ on the counters */
 
 /** Increment a monitor counter under mutex protection.
 Use MONITOR_INC if appropriate mutex protection already exists.
+@param mutex	mutex to acquire and release
 @param monitor	monitor to be incremented by 1
-@param mutex	mutex to acquire and relese */
-# define MONITOR_MUTEX_INC(mutex, monitor)				\
+@param enabled	whether the monitor is enabled */
+#define MONITOR_MUTEX_INC_LOW(mutex, monitor, enabled)			\
 	ut_ad(!mutex_own(mutex));					\
-	if (MONITOR_IS_ON(monitor)) {					\
+	if (enabled) {							\
 		mutex_enter(mutex);					\
 		if (++MONITOR_VALUE(monitor) > MONITOR_MAX_VALUE(monitor)) { \
 			MONITOR_MAX_VALUE(monitor) = MONITOR_VALUE(monitor); \
 		}							\
 		mutex_exit(mutex);					\
 	}
+/** Increment a monitor counter under mutex protection.
+Use MONITOR_INC if appropriate mutex protection already exists.
+@param mutex	mutex to acquire and release
+@param monitor	monitor to be incremented by 1 */
+#define MONITOR_MUTEX_INC(mutex, monitor)				\
+	MONITOR_MUTEX_INC_LOW(mutex, monitor, MONITOR_IS_ON(monitor))
 /** Decrement a monitor counter under mutex protection.
 Use MONITOR_DEC if appropriate mutex protection already exists.
+@param mutex	mutex to acquire and release
 @param monitor	monitor to be decremented by 1
-@param mutex	mutex to acquire and relese */
-# define MONITOR_MUTEX_DEC(mutex, monitor)				\
+@param enabled	whether the monitor is enabled */
+#define MONITOR_MUTEX_DEC_LOW(mutex, monitor, enabled)			\
 	ut_ad(!mutex_own(mutex));					\
 	if (MONITOR_IS_ON(monitor)) {					\
 		mutex_enter(mutex);					\
@@ -565,13 +574,20 @@ Use MONITOR_DEC if appropriate mutex protection already exists.
 		}							\
 		mutex_exit(mutex);					\
 	}
+/** Decrement a monitor counter under mutex protection.
+Use MONITOR_DEC if appropriate mutex protection already exists.
+@param mutex	mutex to acquire and release
+@param monitor	monitor to be decremented by 1 */
+#define MONITOR_MUTEX_DEC(mutex, monitor)				\
+	MONITOR_MUTEX_DEC_LOW(mutex, monitor, MONITOR_IS_ON(monitor))
 
 #if defined HAVE_ATOMIC_BUILTINS_64
 /** Atomically increment a monitor counter.
 Use MONITOR_INC if appropriate mutex protection exists.
-@param monitor	monitor to be incremented by 1 */
-# define MONITOR_ATOMIC_INC(monitor)					\
-	if (MONITOR_IS_ON(monitor)) {					\
+@param monitor	monitor to be incremented by 1
+@param enabled	whether the monitor is enabled */
+# define MONITOR_ATOMIC_INC_LOW(monitor, enabled)			\
+	if (enabled) {					\
 		ib_uint64_t	value;					\
 		value  = os_atomic_increment_uint64(			\
 			(ib_uint64_t*) &MONITOR_VALUE(monitor),	 1);	\
@@ -584,9 +600,10 @@ Use MONITOR_INC if appropriate mutex protection exists.
 
 /** Atomically decrement a monitor counter.
 Use MONITOR_DEC if appropriate mutex protection exists.
-@param monitor	monitor to be decremented by 1 */
-# define MONITOR_ATOMIC_DEC(monitor)					\
-	if (MONITOR_IS_ON(monitor)) {					\
+@param monitor	monitor to be decremented by 1
+@param enabled	whether the monitor is enabled */
+# define MONITOR_ATOMIC_DEC_LOW(monitor, enabled)			\
+	if (enabled) {							\
 		ib_uint64_t	value;					\
 		value = os_atomic_decrement_uint64(			\
 			(ib_uint64_t*) &MONITOR_VALUE(monitor), 1);	\
@@ -617,14 +634,29 @@ srv_mon_free(void);
 
 /** Atomically increment a monitor counter.
 Use MONITOR_INC if appropriate mutex protection exists.
-@param monitor	monitor to be incremented by 1 */
-# define MONITOR_ATOMIC_INC(monitor) MONITOR_MUTEX_INC(&monitor_mutex, monitor)
+@param monitor	monitor to be incremented by 1
+@param enabled	whether the monitor is enabled */
+# define MONITOR_ATOMIC_INC_LOW(monitor, enabled)		\
+	MONITOR_MUTEX_INC_LOW(&monitor_mutex, monitor, enabled)
 /** Atomically decrement a monitor counter.
 Use MONITOR_DEC if appropriate mutex protection exists.
-@param monitor	monitor to be decremented by 1 */
-# define MONITOR_ATOMIC_DEC(monitor) MONITOR_MUTEX_DEC(&monitor_mutex, monitor)
+@param monitor	monitor to be decremented by 1
+@param enabled	whether the monitor is enabled */
+# define MONITOR_ATOMIC_DEC_LOW(monitor, enabled)		\
+	MONITOR_MUTEX_DEC_LOW(&monitor_mutex, monitor, enabled)
 #endif /* HAVE_ATOMIC_BUILTINS_64 */
 
+/** Atomically increment a monitor counter if it is enabled.
+Use MONITOR_INC if appropriate mutex protection exists.
+@param monitor	monitor to be incremented by 1 */
+#define MONITOR_ATOMIC_INC(monitor)				\
+	MONITOR_ATOMIC_INC_LOW(monitor, MONITOR_IS_ON(monitor))
+/** Atomically decrement a monitor counter if it is enabled.
+Use MONITOR_DEC if appropriate mutex protection exists.
+@param monitor	monitor to be decremented by 1 */
+#define MONITOR_ATOMIC_DEC(monitor)				\
+	MONITOR_ATOMIC_DEC_LOW(monitor, MONITOR_IS_ON(monitor))
+
 #define	MONITOR_DEC(monitor)						\
 	if (MONITOR_IS_ON(monitor)) {					\
 		MONITOR_VALUE(monitor)--;				\
diff --git a/storage/xtradb/include/univ.i b/storage/xtradb/include/univ.i
index 6acb0eec319..7497e7f5d05 100644
--- a/storage/xtradb/include/univ.i
+++ b/storage/xtradb/include/univ.i
@@ -304,22 +304,12 @@ definitions: */
 
 #endif /* !UNIV_MUST_NOT_INLINE */
 
-#ifdef _WIN32
-#define UNIV_WORD_SIZE		4
-#elif defined(_WIN64)
-#define UNIV_WORD_SIZE		8
-#else
-/** MySQL config.h generated by GNU autoconf will define SIZEOF_LONG in Posix */
-#define UNIV_WORD_SIZE		SIZEOF_LONG
-#endif
+#define UNIV_WORD_SIZE		SIZEOF_SIZE_T
 
 /** The following alignment is used in memory allocations in memory heap
 management to ensure correct alignment for doubles etc. */
 #define UNIV_MEM_ALIGNMENT	8
 
-/** The following alignment is used in aligning lints etc. */
-#define UNIV_WORD_ALIGNMENT	UNIV_WORD_SIZE
-
 /*
 			DATABASE VERSION CONTROL
 			========================
diff --git a/storage/xtradb/os/os0file.cc b/storage/xtradb/os/os0file.cc
index a30b688ad74..48ae49f28e4 100644
--- a/storage/xtradb/os/os0file.cc
+++ b/storage/xtradb/os/os0file.cc
@@ -2,7 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2009, Percona Inc.
-Copyright (c) 2013, 2017, MariaDB Corporation. All Rights Reserved.
+Copyright (c) 2013, 2017, MariaDB Corporation.
 
 Portions of this file contain modifications contributed and copyrighted
 by Percona Inc.. Those modifications are
@@ -291,21 +291,6 @@ UNIV_INTERN time_t	os_last_printout;
 
 UNIV_INTERN ibool	os_has_said_disk_full	= FALSE;
 
-#if !defined(UNIV_HOTBACKUP)	\
-    && (!defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8)
-/** The mutex protecting the following counts of pending I/O operations */
-static os_ib_mutex_t	os_file_count_mutex;
-#endif /* !UNIV_HOTBACKUP && (!HAVE_ATOMIC_BUILTINS || UNIV_WORD_SIZE < 8) */
-
-/** Number of pending os_file_pread() operations */
-UNIV_INTERN ulint	os_file_n_pending_preads  = 0;
-/** Number of pending os_file_pwrite() operations */
-UNIV_INTERN ulint	os_file_n_pending_pwrites = 0;
-/** Number of pending write operations */
-UNIV_INTERN ulint	os_n_pending_writes = 0;
-/** Number of pending read operations */
-UNIV_INTERN ulint	os_n_pending_reads = 0;
-
 #ifdef UNIV_DEBUG
 # ifndef UNIV_HOTBACKUP
 /**********************************************************************//**
@@ -887,10 +872,6 @@ void
 os_io_init_simple(void)
 /*===================*/
 {
-#if !defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8
-	os_file_count_mutex = os_mutex_create();
-#endif /* !HAVE_ATOMIC_BUILTINS || UNIV_WORD_SIZE < 8 */
-
 	for (ulint i = 0; i < OS_FILE_N_SEEK_MUTEXES; i++) {
 		os_file_seek_mutexes[i] = os_mutex_create();
 	}
@@ -2580,10 +2561,6 @@ os_file_pread(
 	trx_t*		trx)
 {
 	off_t	offs;
-#if defined(HAVE_PREAD) && !defined(HAVE_BROKEN_PREAD)
-	ssize_t	n_bytes;
-	ssize_t n_read;
-#endif /* HAVE_PREAD && !HAVE_BROKEN_PREAD */
 	ulint		sec;
 	ulint		ms;
 	ib_uint64_t	start_time;
@@ -2613,22 +2590,16 @@ os_file_pread(
 	} else {
 		start_time = 0;
 	}
-#if defined(HAVE_PREAD) && !defined(HAVE_BROKEN_PREAD)
-#if defined(HAVE_ATOMIC_BUILTINS) && UNIV_WORD_SIZE == 8
-	(void) os_atomic_increment_ulint(&os_n_pending_reads, 1);
-	(void) os_atomic_increment_ulint(&os_file_n_pending_preads, 1);
-	MONITOR_ATOMIC_INC(MONITOR_OS_PENDING_READS);
-#else
-	os_mutex_enter(os_file_count_mutex);
-	os_file_n_pending_preads++;
-	os_n_pending_reads++;
-	MONITOR_INC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
-#endif /* HAVE_ATOMIC_BUILTINS && UNIV_WORD == 8 */
+
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_READS);
+#ifdef HAVE_PREAD
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_READS, monitor);
+
+	ssize_t	n_bytes;
 
 	/* Handle partial reads and signal interruptions correctly */
 	for (n_bytes = 0; n_bytes < (ssize_t) n; ) {
-		n_read = pread(file, buf, (ssize_t)n - n_bytes, offs);
+		ssize_t n_read = pread(file, buf, (ssize_t)n - n_bytes, offs);
 		if (n_read > 0) {
 			n_bytes += n_read;
 			offs += n_read;
@@ -2640,17 +2611,7 @@ os_file_pread(
 		}
 	}
 
-#if defined(HAVE_ATOMIC_BUILTINS) && UNIV_WORD_SIZE == 8
-	(void) os_atomic_decrement_ulint(&os_n_pending_reads, 1);
-	(void) os_atomic_decrement_ulint(&os_file_n_pending_preads, 1);
-	MONITOR_ATOMIC_DEC(MONITOR_OS_PENDING_READS);
-#else
-	os_mutex_enter(os_file_count_mutex);
-	os_file_n_pending_preads--;
-	os_n_pending_reads--;
-	MONITOR_DEC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
-#endif /* !HAVE_ATOMIC_BUILTINS || UNIV_WORD == 8 */
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 	if (UNIV_UNLIKELY(start_time != 0))
 	{
@@ -2669,15 +2630,7 @@ os_file_pread(
 		ulint	i;
 #endif /* !UNIV_HOTBACKUP */
 
-#if defined(HAVE_ATOMIC_BUILTINS) && UNIV_WORD_SIZE == 8
-		(void) os_atomic_increment_ulint(&os_n_pending_reads, 1);
-		MONITOR_ATOMIC_INC(MONITOR_OS_PENDING_READS);
-#else
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_reads++;
-		MONITOR_INC(MONITOR_OS_PENDING_READS);
-		os_mutex_exit(os_file_count_mutex);
-#endif /* HAVE_ATOMIC_BUILTINS && UNIV_WORD == 8 */
+		MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_READS, monitor);
 #ifndef UNIV_HOTBACKUP
 		/* Protect the seek / read operation with a mutex */
 		i = ((ulint) file) % OS_FILE_N_SEEK_MUTEXES;
@@ -2707,15 +2660,7 @@ os_file_pread(
 		os_mutex_exit(os_file_seek_mutexes[i]);
 #endif /* !UNIV_HOTBACKUP */
 
-#if defined(HAVE_ATOMIC_BUILTINS) && UNIV_WORD_SIZE == 8
-		(void) os_atomic_decrement_ulint(&os_n_pending_reads, 1);
-		MONITOR_ATOIC_DEC(MONITOR_OS_PENDING_READS);
-#else
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_reads--;
-		MONITOR_DEC(MONITOR_OS_PENDING_READS);
-		os_mutex_exit(os_file_count_mutex);
-#endif /* HAVE_ATOMIC_BUILTINS && UNIV_WORD_SIZE == 8 */
+		MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 		if (UNIV_UNLIKELY(start_time != 0)
 		{
@@ -2761,18 +2706,9 @@ os_file_pwrite(
 
 	os_n_file_writes++;
 
-#if defined(HAVE_PWRITE) && !defined(HAVE_BROKEN_PREAD)
-#if !defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8
-	os_mutex_enter(os_file_count_mutex);
-	os_file_n_pending_pwrites++;
-	os_n_pending_writes++;
-	MONITOR_INC(MONITOR_OS_PENDING_WRITES);
-	os_mutex_exit(os_file_count_mutex);
-#else
-	(void) os_atomic_increment_ulint(&os_n_pending_writes, 1);
-	(void) os_atomic_increment_ulint(&os_file_n_pending_pwrites, 1);
-	MONITOR_ATOMIC_INC(MONITOR_OS_PENDING_WRITES);
-#endif /* !HAVE_ATOMIC_BUILTINS || UNIV_WORD < 8 */
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_WRITES);
+#ifdef HAVE_PWRITE
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 	/* Handle partial writes and signal interruptions correctly */
 	for (ret = 0; ret < (ssize_t) n; ) {
@@ -2791,17 +2727,7 @@ os_file_pwrite(
 		}
 	}
 
-#if !defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8
-	os_mutex_enter(os_file_count_mutex);
-	os_file_n_pending_pwrites--;
-	os_n_pending_writes--;
-	MONITOR_DEC(MONITOR_OS_PENDING_WRITES);
-	os_mutex_exit(os_file_count_mutex);
-#else
-	(void) os_atomic_decrement_ulint(&os_n_pending_writes, 1);
-	(void) os_atomic_decrement_ulint(&os_file_n_pending_pwrites, 1);
-	MONITOR_ATOMIC_DEC(MONITOR_OS_PENDING_WRITES);
-#endif /* !HAVE_ATOMIC_BUILTINS || UNIV_WORD < 8 */
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 	return(ret);
 #else
@@ -2811,10 +2737,7 @@ os_file_pwrite(
 		ulint	i;
 # endif /* !UNIV_HOTBACKUP */
 
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_writes++;
-		MONITOR_INC(MONITOR_OS_PENDING_WRITES);
-		os_mutex_exit(os_file_count_mutex);
+		MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 # ifndef UNIV_HOTBACKUP
 		/* Protect the seek / write operation with a mutex */
@@ -2848,14 +2771,10 @@ func_exit:
 		os_mutex_exit(os_file_seek_mutexes[i]);
 # endif /* !UNIV_HOTBACKUP */
 
-		os_mutex_enter(os_file_count_mutex);
-		os_n_pending_writes--;
-		MONITOR_DEC(MONITOR_OS_PENDING_WRITES);
-		os_mutex_exit(os_file_count_mutex);
-
+		MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 		return(ret);
 	}
-#endif /* !UNIV_HOTBACKUP */
+#endif /* HAVE_PWRITE */
 }
 #endif
 
@@ -2887,15 +2806,13 @@ os_file_read_func(
 
 	os_n_file_reads++;
 	os_bytes_read_since_printout += n;
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_READS);
 
 try_again:
 	ut_ad(buf);
 	ut_ad(n > 0);
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_reads++;
-	MONITOR_INC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 	memset (&overlapped, 0, sizeof (overlapped));
 	overlapped.Offset = (DWORD)(offset & 0xFFFFFFFF);
@@ -2908,10 +2825,7 @@ try_again:
 	else if(GetLastError() == ERROR_IO_PENDING) {
 		ret = GetOverlappedResult(file, &overlapped, (DWORD *)&len, TRUE);
         }
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_reads--;
-	MONITOR_DEC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 	if (ret && len == n) {
 		return(TRUE);
@@ -2995,15 +2909,13 @@ os_file_read_no_error_handling_func(
 
 	os_n_file_reads++;
 	os_bytes_read_since_printout += n;
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_READS);
 
 try_again:
 	ut_ad(buf);
 	ut_ad(n > 0);
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_reads++;
-	MONITOR_INC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 	memset (&overlapped, 0, sizeof (overlapped));
 	overlapped.Offset = (DWORD)(offset & 0xFFFFFFFF);
@@ -3016,10 +2928,7 @@ try_again:
 	else if(GetLastError() == ERROR_IO_PENDING) {
 		ret = GetOverlappedResult(file, &overlapped, (DWORD *)&len, TRUE);
 	}
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_reads--;
-	MONITOR_DEC(MONITOR_OS_PENDING_READS);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_READS, monitor);
 
 	if (ret && len == n) {
 		return(TRUE);
@@ -3113,12 +3022,10 @@ os_file_write_func(
 
 	ut_ad(buf);
 	ut_ad(n > 0);
+	const bool monitor = MONITOR_IS_ON(MONITOR_OS_PENDING_WRITES);
 retry:
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_writes++;
-	MONITOR_INC(MONITOR_OS_PENDING_WRITES);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_INC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 	memset (&overlapped, 0, sizeof (overlapped));
 	overlapped.Offset = (DWORD)(offset & 0xFFFFFFFF);
@@ -3133,10 +3040,7 @@ retry:
 		ret = GetOverlappedResult(file, &overlapped, (DWORD *)&len, TRUE);
 	}
 
-	os_mutex_enter(os_file_count_mutex);
-	os_n_pending_writes--;
-	MONITOR_DEC(MONITOR_OS_PENDING_WRITES);
-	os_mutex_exit(os_file_count_mutex);
+	MONITOR_ATOMIC_DEC_LOW(MONITOR_OS_PENDING_WRITES, monitor);
 
 	if (ret && len == n) {
 
@@ -4230,10 +4134,6 @@ os_aio_free(void)
 		}
 	}
 
-#if !defined(HAVE_ATOMIC_BUILTINS) || UNIV_WORD_SIZE < 8
-	os_mutex_free(os_file_count_mutex);
-#endif /* !HAVE_ATOMIC_BUILTINS || UNIV_WORD_SIZE < 8 */
-
 	for (ulint i = 0; i < OS_FILE_N_SEEK_MUTEXES; i++) {
 		os_mutex_free(os_file_seek_mutexes[i]);
 	}
@@ -5909,19 +5809,24 @@ os_aio_print(
 	time_elapsed = 0.001 + difftime(current_time, os_last_printout);
 
 	fprintf(file,
-		"Pending flushes (fsync) log: %lu; buffer pool: %lu\n"
-		"%lu OS file reads, %lu OS file writes, %lu OS fsyncs\n",
-		(ulong) fil_n_pending_log_flushes,
-		(ulong) fil_n_pending_tablespace_flushes,
-		(ulong) os_n_file_reads,
-		(ulong) os_n_file_writes,
-		(ulong) os_n_fsyncs);
-
-	if (os_file_n_pending_preads != 0 || os_file_n_pending_pwrites != 0) {
+		"Pending flushes (fsync) log: " ULINTPF
+		"; buffer pool: " ULINTPF "\n"
+		ULINTPF " OS file reads, "
+		ULINTPF " OS file writes, "
+		ULINTPF " OS fsyncs\n",
+		fil_n_pending_log_flushes,
+		fil_n_pending_tablespace_flushes,
+		os_n_file_reads,
+		os_n_file_writes,
+		os_n_fsyncs);
+
+	const ulint n_reads = MONITOR_VALUE(MONITOR_OS_PENDING_READS);
+	const ulint n_writes = MONITOR_VALUE(MONITOR_OS_PENDING_WRITES);
+
+	if (n_reads != 0 || n_writes != 0) {
 		fprintf(file,
-			"%lu pending preads, %lu pending pwrites\n",
-			(ulong) os_file_n_pending_preads,
-			(ulong) os_file_n_pending_pwrites);
+			ULINTPF " pending reads, " ULINTPF " pending writes\n",
+			n_reads, n_writes);
 	}
 
 	if (os_n_file_reads == os_n_file_reads_old) {
diff --git a/storage/xtradb/srv/srv0mon.cc b/storage/xtradb/srv/srv0mon.cc
index 4a709160ea6..ea21a4c1454 100644
--- a/storage/xtradb/srv/srv0mon.cc
+++ b/storage/xtradb/srv/srv0mon.cc
@@ -2,6 +2,7 @@
 
 Copyright (c) 2010, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
+Copyright (c) 2017, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -643,11 +644,11 @@ static monitor_info_t	innodb_counter_info[] =
 	 MONITOR_DEFAULT_START, MONITOR_OVLD_OS_FSYNC},
 
 	{"os_pending_reads", "os", "Number of reads pending",
-	 MONITOR_NONE,
+	 MONITOR_DEFAULT_ON,
 	 MONITOR_DEFAULT_START, MONITOR_OS_PENDING_READS},
 
 	{"os_pending_writes", "os", "Number of writes pending",
-	 MONITOR_NONE,
+	 MONITOR_DEFAULT_ON,
 	 MONITOR_DEFAULT_START, MONITOR_OS_PENDING_WRITES},
 
 	{"os_log_bytes_written", "os",
diff --git a/storage/xtradb/srv/srv0srv.cc b/storage/xtradb/srv/srv0srv.cc
index ffa1e36ebcd..c47119e63cf 100644
--- a/storage/xtradb/srv/srv0srv.cc
+++ b/storage/xtradb/srv/srv0srv.cc
@@ -1735,10 +1735,10 @@ srv_export_innodb_status(void)
 	mutex_enter(&srv_innodb_monitor_mutex);
 
 	export_vars.innodb_data_pending_reads =
-		os_n_pending_reads;
+		MONITOR_VALUE(MONITOR_OS_PENDING_READS);
 
 	export_vars.innodb_data_pending_writes =
-		os_n_pending_writes;
+		MONITOR_VALUE(MONITOR_OS_PENDING_WRITES);
 
 	export_vars.innodb_data_pending_fsyncs =
 		fil_n_pending_log_flushes
diff --git a/storage/xtradb/sync/sync0arr.cc b/storage/xtradb/sync/sync0arr.cc
index e16eddae80c..7325cb49145 100644
--- a/storage/xtradb/sync/sync0arr.cc
+++ b/storage/xtradb/sync/sync0arr.cc
@@ -1161,9 +1161,10 @@ sync_array_print_long_waits(
 		now the values of pending calls of these. */
 
 		fprintf(stderr,
-			"InnoDB: Pending preads %lu, pwrites %lu\n",
-			(ulong) os_file_n_pending_preads,
-			(ulong) os_file_n_pending_pwrites);
+			"InnoDB: Pending reads " UINT64PF
+			", writes " UINT64PF "\n",
+			MONITOR_VALUE(MONITOR_OS_PENDING_READS),
+			MONITOR_VALUE(MONITOR_OS_PENDING_WRITES));
 
 		srv_print_innodb_monitor = TRUE;
 		os_event_set(srv_monitor_event);