Module Name: src
Committed By: riastradh
Date: Thu Jul 13 13:34:15 UTC 2023
Modified Files:
src/sys/arch/x86/include: cpu.h
src/sys/arch/xen/xen: xen_clock.c
Log Message:
xen: Record event when local view of timecounter is behind global.
To generate a diff of this commit:
cvs rdiff -u -r1.134 -r1.135 src/sys/arch/x86/include/cpu.h
cvs rdiff -u -r1.10 -r1.11 src/sys/arch/xen/xen/xen_clock.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/include/cpu.h
diff -u src/sys/arch/x86/include/cpu.h:1.134 src/sys/arch/x86/include/cpu.h:1.135
--- src/sys/arch/x86/include/cpu.h:1.134 Thu Jul 13 12:06:20 2023
+++ src/sys/arch/x86/include/cpu.h Thu Jul 13 13:34:15 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: cpu.h,v 1.134 2023/07/13 12:06:20 riastradh Exp $ */
+/* $NetBSD: cpu.h,v 1.135 2023/07/13 13:34:15 riastradh Exp $ */
/*
* Copyright (c) 1990 The Regents of the University of California.
@@ -325,6 +325,7 @@ struct cpu_info {
struct evcnt ci_xen_raw_systime_backwards_evcnt;
struct evcnt ci_xen_systime_backwards_hardclock_evcnt;
struct evcnt ci_xen_missed_hardclock_evcnt;
+ struct evcnt ci_xen_timecounter_backwards_evcnt;
#endif /* XEN */
#if defined(GPROF) && defined(MULTIPROCESSOR)
Index: src/sys/arch/xen/xen/xen_clock.c
diff -u src/sys/arch/xen/xen/xen_clock.c:1.10 src/sys/arch/xen/xen/xen_clock.c:1.11
--- src/sys/arch/xen/xen/xen_clock.c:1.10 Fri Jul 7 15:13:41 2023
+++ src/sys/arch/xen/xen/xen_clock.c Thu Jul 13 13:34:15 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: xen_clock.c,v 1.10 2023/07/07 15:13:41 bouyer Exp $ */
+/* $NetBSD: xen_clock.c,v 1.11 2023/07/13 13:34:15 riastradh Exp $ */
/*-
* Copyright (c) 2017, 2018 The NetBSD Foundation, Inc.
@@ -36,7 +36,7 @@
#endif
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xen_clock.c,v 1.10 2023/07/07 15:13:41 bouyer Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xen_clock.c,v 1.11 2023/07/13 13:34:15 riastradh Exp $");
#include <sys/param.h>
#include <sys/types.h>
@@ -112,6 +112,11 @@ SDT_PROBE_DEFINE7(sdt, xen, clock, systi
"uint64_t"/*tsc*/,
"uint64_t"/*systime_ns*/);
+SDT_PROBE_DEFINE3(sdt, xen, timecounter, backward,
+ "uint64_t"/*local*/,
+ "uint64_t"/*skew*/,
+ "uint64_t"/*global*/);
+
SDT_PROBE_DEFINE2(sdt, xen, hardclock, systime__backward,
"uint64_t"/*last_systime_ns*/,
"uint64_t"/*this_systime_ns*/);
@@ -510,7 +515,7 @@ static uint64_t
xen_global_systime_ns(void)
{
struct cpu_info *ci;
- uint64_t local, global, result;
+ uint64_t local, global, skew, result;
/*
* Find the local timecount on this CPU, and make sure it does
@@ -524,13 +529,24 @@ xen_global_systime_ns(void)
ci = curcpu();
do {
local = xen_vcputime_systime_ns();
- local += ci->ci_xen_systime_ns_skew;
+ skew = ci->ci_xen_systime_ns_skew;
global = xen_global_systime_ns_stamp;
- if (__predict_false(local < global + 1)) {
+ if (__predict_false(local + skew < global + 1)) {
+ SDT_PROBE3(sdt, xen, timecounter, backward,
+ local, skew, global);
+#if XEN_CLOCK_DEBUG
+ device_printf(ci->ci_dev,
+ "xen timecounter went backwards:"
+ " local=%"PRIu64" skew=%"PRIu64" global=%"PRIu64","
+ " adding %"PRIu64" to skew\n",
+ local, skew, global, global + 1 - (local + skew));
+#endif
+ ci->ci_xen_timecounter_backwards_evcnt.ev_count++;
result = global + 1;
- ci->ci_xen_systime_ns_skew += global + 1 - local;
+ ci->ci_xen_systime_ns_skew += global + 1 -
+ (local + skew);
} else {
- result = local;
+ result = local + skew;
}
} while (atomic_cas_64(&xen_global_systime_ns_stamp, global, result)
!= global);
@@ -831,6 +847,9 @@ xen_initclocks(void)
evcnt_attach_dynamic(&ci->ci_xen_missed_hardclock_evcnt,
EVCNT_TYPE_INTR, NULL, device_xname(ci->ci_dev),
"missed hardclock");
+ evcnt_attach_dynamic(&ci->ci_xen_timecounter_backwards_evcnt,
+ EVCNT_TYPE_INTR, NULL, device_xname(ci->ci_dev),
+ "timecounter went backwards");
/* Fire up the clocks. */
xen_resumeclocks(ci);
