Module Name: src
Committed By: riastradh
Date: Tue Dec 3 04:57:25 UTC 2019
Modified Files:
src/sys/arch/x86/x86: bus_space.c
Log Message:
Skip fences in bus_space_barrier on I/O space.
I/O operations are issued in program order. Not that I/O operations
are usually a performance bottleneck anyway, but maybe it is slightly
cheaper to avoid stalling on store buffers or pending loads, and
there's very little cost to the skipping criterion here.
To generate a diff of this commit:
cvs rdiff -u -r1.42 -r1.43 src/sys/arch/x86/x86/bus_space.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/x86/x86/bus_space.c
diff -u src/sys/arch/x86/x86/bus_space.c:1.42 src/sys/arch/x86/x86/bus_space.c:1.43
--- src/sys/arch/x86/x86/bus_space.c:1.42 Mon Dec 2 08:33:52 2019
+++ src/sys/arch/x86/x86/bus_space.c Tue Dec 3 04:57:25 2019
@@ -1,4 +1,4 @@
-/* $NetBSD: bus_space.c,v 1.42 2019/12/02 08:33:52 riastradh Exp $ */
+/* $NetBSD: bus_space.c,v 1.43 2019/12/03 04:57:25 riastradh Exp $ */
/*-
* Copyright (c) 1996, 1997, 1998 The NetBSD Foundation, Inc.
@@ -31,7 +31,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: bus_space.c,v 1.42 2019/12/02 08:33:52 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bus_space.c,v 1.43 2019/12/03 04:57:25 riastradh Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -878,6 +878,10 @@ bus_space_barrier(bus_space_tag_t tag, b
bus_size_t offset, bus_size_t len, int flags)
{
+ /* I/O instructions always happen in program order. */
+ if (x86_bus_space_is_io(tag))
+ return;
+
/*
* For default mappings, which are mapped with UC-type memory
* regions, all loads and stores are issued in program order.
