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Introduce the sysclock_getsnapshot() and sysclock_snap2bintime() KPIs. The

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sysclock_getsnapshot() function allows the caller to obtain a snapshot of all
the system clock and timecounter state required to create time stamps at a later
point. The sysclock_snap2bintime() function converts a previously obtained
snapshot into a bintime time stamp according to the specified flags e.g. which
system clock, uptime vs absolute time, etc.

These KPIs enable useful functionality, including direct comparison of the
feedback and feed-forward system clocks and generation of multiple time stamps
with different formats from a single timecounter read.

Committed on behalf of Julien Ridoux and Darryl Veitch from the University of
Melbourne, Australia, as part of the FreeBSD Foundation funded "Feed-Forward
Clock Synchronization Algorithms" project.

For more information, see http://www.synclab.org/radclock/

In collaboration with:	Julien Ridoux (jridoux at unimelb edu au)
This commit is contained in:
Lawrence Stewart 2011-12-24 01:32:01 +00:00
parent da914858e1
commit 6cedd609b7
3 changed files with 210 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
sys/kern/kern_ntptime.c
View File

@ -148,13 +148,13 @@ typedef int64_t l_fp;
#define SHIFT_FLL 2 /* FLL loop gain (shift) */
static int time_state = TIME_OK; /* clock state */
static int time_status = STA_UNSYNC; /* clock status bits */
int time_status = STA_UNSYNC; /* clock status bits */
static long time_tai; /* TAI offset (s) */
static long time_monitor; /* last time offset scaled (ns) */
static long time_constant; /* poll interval (shift) (s) */
static long time_precision = 1; /* clock precision (ns) */
static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
static long time_reftime; /* time at last adjustment (s) */
static l_fp time_offset; /* time offset (ns) */
static l_fp time_freq; /* frequency offset (ns/s) */

144
sys/kern/kern_tc.c
View File

@ -28,9 +28,7 @@ __FBSDID("$FreeBSD$");
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#ifdef FFCLOCK
#include <sys/timeffc.h>
#endif
#include <sys/timepps.h>
#include <sys/timetc.h>
#include <sys/timex.h>
@ -461,8 +459,6 @@ getmicrotime(struct timeval *tvp)
* necessary.
*/
int sysclock_active = SYSCLOCK_FBCK;
/* Feed-forward clock estimates kept updated by the synchronization daemon. */
struct ffclock_estimate ffclock_estimate;
struct bintime ffclock_boottime; /* Feed-forward boot time estimate. */
@ -956,8 +952,148 @@ getmicrotime(struct timeval *tvp)
getmicrouptime_fromclock(tvp, sysclock_active);
}
#endif /* FFCLOCK */
/*
* System clock currently providing time to the system. Modifiable via sysctl
* when the FFCLOCK option is defined.
*/
int sysclock_active = SYSCLOCK_FBCK;
/* Internal NTP status and error estimates. */
extern int time_status;
extern long time_esterror;
/*
* Take a snapshot of sysclock data which can be used to compare system clocks
* and generate timestamps after the fact.
*/
void
sysclock_getsnapshot(struct sysclock_snap *clock_snap, int fast)
{
struct fbclock_info *fbi;
struct timehands *th;
struct bintime bt;
unsigned int delta, gen;
#ifdef FFCLOCK
ffcounter ffcount;
struct fftimehands *ffth;
struct ffclock_info *ffi;
struct ffclock_estimate cest;
ffi = &clock_snap->ff_info;
#endif
fbi = &clock_snap->fb_info;
delta = 0;
do {
th = timehands;
gen = th->th_generation;
fbi->th_scale = th->th_scale;
fbi->tick_time = th->th_offset;
#ifdef FFCLOCK
ffth = fftimehands;
ffi->tick_time = ffth->tick_time_lerp;
ffi->tick_time_lerp = ffth->tick_time_lerp;
ffi->period = ffth->cest.period;
ffi->period_lerp = ffth->period_lerp;
clock_snap->ffcount = ffth->tick_ffcount;
cest = ffth->cest;
#endif
if (!fast)
delta = tc_delta(th);
} while (gen == 0 || gen != th->th_generation);
clock_snap->delta = delta;
clock_snap->sysclock_active = sysclock_active;
/* Record feedback clock status and error. */
clock_snap->fb_info.status = time_status;
/* XXX: Very crude estimate of feedback clock error. */
bt.sec = time_esterror / 1000000;
bt.frac = ((time_esterror - bt.sec) * 1000000) *
(uint64_t)18446744073709ULL;
clock_snap->fb_info.error = bt;
#ifdef FFCLOCK
if (!fast)
clock_snap->ffcount += delta;
/* Record feed-forward clock leap second adjustment. */
ffi->leapsec_adjustment = cest.leapsec_total;
if (clock_snap->ffcount > cest.leapsec_next)
ffi->leapsec_adjustment -= cest.leapsec;
/* Record feed-forward clock status and error. */
clock_snap->ff_info.status = cest.status;
ffcount = clock_snap->ffcount - cest.update_ffcount;
ffclock_convert_delta(ffcount, cest.period, &bt);
/* 18446744073709 = int(2^64/1e12), err_bound_rate in [ps/s]. */
bintime_mul(&bt, cest.errb_rate * (uint64_t)18446744073709ULL);
/* 18446744073 = int(2^64 / 1e9), since err_abs in [ns]. */
bintime_addx(&bt, cest.errb_abs * (uint64_t)18446744073ULL);
clock_snap->ff_info.error = bt;
#endif
}
/*
* Convert a sysclock snapshot into a struct bintime based on the specified
* clock source and flags.
*/
int
sysclock_snap2bintime(struct sysclock_snap *cs, struct bintime *bt,
int whichclock, uint32_t flags)
{
#ifdef FFCLOCK
struct bintime bt2;
uint64_t period;
#endif
switch (whichclock) {
case SYSCLOCK_FBCK:
*bt = cs->fb_info.tick_time;
/* If snapshot was created with !fast, delta will be >0. */
if (cs->delta > 0)
bintime_addx(bt, cs->fb_info.th_scale * cs->delta);
if ((flags & FBCLOCK_UPTIME) == 0)
bintime_add(bt, &boottimebin);
break;
#ifdef FFCLOCK
case SYSCLOCK_FFWD:
if (flags & FFCLOCK_LERP) {
*bt = cs->ff_info.tick_time_lerp;
period = cs->ff_info.period_lerp;
} else {
*bt = cs->ff_info.tick_time;
period = cs->ff_info.period;
}
/* If snapshot was created with !fast, delta will be >0. */
if (cs->delta > 0) {
ffclock_convert_delta(cs->delta, period, &bt2);
bintime_add(bt, &bt2);
}
/* Leap second adjustment. */
if (flags & FFCLOCK_LEAPSEC)
bt->sec -= cs->ff_info.leapsec_adjustment;
/* Boot time adjustment, for uptime/monotonic clocks. */
if (flags & FFCLOCK_UPTIME)
bintime_sub(bt, &ffclock_boottime);
#endif
default:
return (EINVAL);
break;
}
return (0);
}
/*
* Initialize a new timecounter and possibly use it.
*/

80
sys/sys/timeffc.h
View File

@ -81,19 +81,75 @@ extern int sysclock_active;
#define FFCLOCK_STA_WARMUP 2
/*
* Clock flags to select how the feed-forward counter is converted to absolute
* time by ffclock_convert_abs().
* FAST: do not read the hardware counter, return feed-forward clock time
* at last tick. The time returned has the resolution of the kernel
* tick (1/hz [s]).
* LERP: linear interpolation of ffclock time to guarantee monotonic time.
* LEAPSEC: include leap seconds.
* UPTIME: removes time of boot.
* Flags for use by sysclock_snap2bintime() and various ffclock_ functions to
* control how the timecounter hardware is read and how the hardware snapshot is
* converted into absolute time.
* {FB|FF}CLOCK_FAST: Do not read the hardware counter, instead using the
* value at last tick. The time returned has a resolution
* of the kernel tick timer (1/hz [s]).
* FFCLOCK_LERP: Linear interpolation of ffclock time to guarantee
* monotonic time.
* FFCLOCK_LEAPSEC: Include leap seconds.
* {FB|FF}CLOCK_UPTIME: Time stamp should be relative to system boot, not epoch.
*/
#define FFCLOCK_FAST 1
#define FFCLOCK_LERP 2
#define FFCLOCK_LEAPSEC 4
#define FFCLOCK_UPTIME 8
#define FFCLOCK_FAST 0x00000001
#define FFCLOCK_LERP 0x00000002
#define FFCLOCK_LEAPSEC 0x00000004
#define FFCLOCK_UPTIME 0x00000008
#define FFCLOCK_MASK 0x0000ffff
#define FBCLOCK_FAST 0x00010000 /* Currently unused. */
#define FBCLOCK_UPTIME 0x00020000
#define FBCLOCK_MASK 0xffff0000
/*
* Feedback clock specific info structure. The feedback clock's estimation of
* clock error is an absolute figure determined by the NTP algorithm. The status
* is determined by the userland daemon.
*/
struct fbclock_info {
struct bintime error;
struct bintime tick_time;
uint64_t th_scale;
int status;
};
/*
* Feed-forward clock specific info structure. The feed-forward clock's
* estimation of clock error is an upper bound, which although potentially
* looser than the feedback clock equivalent, is much more reliable. The status
* is determined by the userland daemon.
*/
struct ffclock_info {
struct bintime error;
struct bintime tick_time;
struct bintime tick_time_lerp;
uint64_t period;
uint64_t period_lerp;
int leapsec_adjustment;
int status;
};
/*
* Snapshot of system clocks and related information. Holds time read from each
* clock based on a single read of the active hardware timecounter, as well as
* respective clock information such as error estimates and the ffcounter value
* at the time of the read.
*/
struct sysclock_snap {
struct fbclock_info fb_info;
struct ffclock_info ff_info;
ffcounter ffcount;
unsigned int delta;
int sysclock_active;
};
/* Take a snapshot of the system clocks and related information. */
void sysclock_getsnapshot(struct sysclock_snap *clock_snap, int fast);
/* Convert a timestamp from the selected system clock into bintime. */
int sysclock_snap2bintime(struct sysclock_snap *cs, struct bintime *bt,
int whichclock, uint32_t flags);
/* Resets feed-forward clock from RTC */
void ffclock_reset_clock(struct timespec *ts);