Module Name: src
Committed By: ad
Date: Thu Apr 23 20:38:33 UTC 2020
Modified Files:
src/sys/arch/x86/x86: tsc.c
Log Message:
When computing TSC skew make 8 measurements and use the average.
To generate a diff of this commit:
cvs rdiff -u -r1.41 -r1.42 src/sys/arch/x86/x86/tsc.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/tsc.c
diff -u src/sys/arch/x86/x86/tsc.c:1.41 src/sys/arch/x86/x86/tsc.c:1.42
--- src/sys/arch/x86/x86/tsc.c:1.41 Tue Apr 21 02:56:37 2020
+++ src/sys/arch/x86/x86/tsc.c Thu Apr 23 20:38:33 2020
@@ -1,7 +1,7 @@
-/* $NetBSD: tsc.c,v 1.41 2020/04/21 02:56:37 msaitoh Exp $ */
+/* $NetBSD: tsc.c,v 1.42 2020/04/23 20:38:33 ad Exp $ */
/*-
- * Copyright (c) 2008 The NetBSD Foundation, Inc.
+ * Copyright (c) 2008, 2020 The NetBSD Foundation, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -27,7 +27,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tsc.c,v 1.41 2020/04/21 02:56:37 msaitoh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tsc.c,v 1.42 2020/04/23 20:38:33 ad Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -229,13 +229,17 @@ tsc_read_bp(struct cpu_info *ci, uint64_
void
tsc_sync_bp(struct cpu_info *ci)
{
- uint64_t bptsc, aptsc;
+ int64_t bptsc, aptsc, bsum = 0, asum = 0;
tsc_read_bp(ci, &bptsc, &aptsc); /* discarded - cache effects */
- tsc_read_bp(ci, &bptsc, &aptsc);
+ for (int i = 0; i < 8; i++) {
+ tsc_read_bp(ci, &bptsc, &aptsc);
+ bsum += bptsc;
+ asum += aptsc;
+ }
/* Compute final value to adjust for skew. */
- ci->ci_data.cpu_cc_skew = bptsc - aptsc;
+ ci->ci_data.cpu_cc_skew = (bsum - asum) >> 3;
}
/*
@@ -270,7 +274,9 @@ tsc_sync_ap(struct cpu_info *ci)
{
tsc_post_ap(ci);
- tsc_post_ap(ci);
+ for (int i = 0; i < 8; i++) {
+ tsc_post_ap(ci);
+ }
}
static void
