Aren
/
NetBSD
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

xen: Record event when local view of timecounter is behind global.

This commit is contained in:
riastradh 2023-07-13 13:34:15 +00:00
parent 589aa4ee58
commit 93889e4a72
2 changed files with 28 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
sys/arch/x86/include/cpu.h
View File

@ -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)

33
sys/arch/xen/xen/xen_clock.c
View File

@ -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, systime__backward,
"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);