| Message ID | 1234894875-10268-1-git-send-email-Aaro.Koskinen@nokia.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Tony Lindgren |
| Headers | show |
* Aaro Koskinen <Aaro.Koskinen@nokia.com> [090217 10:27]: > After my OMAP3 board has been running for a while, I'm seeing weird > latency traces like this: > > sh-1574 0d.h2 153us : do_timer (tick_do_update_jiffies64) > sh-1574 0d.h2 153us : update_wall_time (do_timer) > sh-1574 0d.h2 153us!: omap_32k_read (update_wall_time) > sh-1574 0d.h2 1883us : update_xtime_cache (update_wall_time) > sh-1574 0d.h2 1883us : clocksource_get_next (update_wall_time) > sh-1574 0d.h2 1883us+: _spin_lock_irqsave (clocksource_get_next) > > and after a while: > > sh-17818 0d.h3 153us : do_timer (tick_do_update_jiffies64) > sh-17818 0d.h3 153us : update_wall_time (do_timer) > sh-17818 0d.h3 153us!: omap_32k_read (update_wall_time) > sh-17818 0d.h3 1915us : update_xtime_cache (update_wall_time) > sh-17818 0d.h3 1915us+: clocksource_get_next (update_wall_time) > sh-17818 0d.h3 1945us : _spin_lock_irqsave (clocksource_get_next) > > Turns out that sched_clock() is using cyc2ns(), which returns NTP > adjusted time. The sched_clock() frequency should not be adjusted. The > patch deletes omap_32k_ticks_to_nsecs() and rewrites sched_clock() > to do the conversion using the constant multiplier. Nice catch! Applying to linux-omap and omap-fixes. Tony > Signed-off-by: Aaro Koskinen <Aaro.Koskinen@nokia.com> > --- > arch/arm/plat-omap/common.c | 14 +++++--------- > 1 files changed, 5 insertions(+), 9 deletions(-) > > diff --git a/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c > index 8c53125..2866612 100644 > --- a/arch/arm/plat-omap/common.c > +++ b/arch/arm/plat-omap/common.c > @@ -220,20 +220,16 @@ static struct clocksource clocksource_32k = { > }; > > /* > - * Rounds down to nearest nsec. > - */ > -unsigned long long omap_32k_ticks_to_nsecs(unsigned long ticks_32k) > -{ > - return cyc2ns(&clocksource_32k, ticks_32k); > -} > - > -/* > * Returns current time from boot in nsecs. It's OK for this to wrap > * around for now, as it's just a relative time stamp. > */ > unsigned long long sched_clock(void) > { > - return omap_32k_ticks_to_nsecs(omap_32k_read()); > + unsigned long long ret; > + > + ret = (unsigned long long)omap_32k_read(); > + ret = (ret * clocksource_32k.mult_orig) >> clocksource_32k.shift; > + return ret; > } > > static int __init omap_init_clocksource_32k(void) > -- > 1.5.4.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c index 8c53125..2866612 100644 --- a/arch/arm/plat-omap/common.c +++ b/arch/arm/plat-omap/common.c @@ -220,20 +220,16 @@ static struct clocksource clocksource_32k = { }; /* - * Rounds down to nearest nsec. - */ -unsigned long long omap_32k_ticks_to_nsecs(unsigned long ticks_32k) -{ - return cyc2ns(&clocksource_32k, ticks_32k); -} - -/* * Returns current time from boot in nsecs. It's OK for this to wrap * around for now, as it's just a relative time stamp. */ unsigned long long sched_clock(void) { - return omap_32k_ticks_to_nsecs(omap_32k_read()); + unsigned long long ret; + + ret = (unsigned long long)omap_32k_read(); + ret = (ret * clocksource_32k.mult_orig) >> clocksource_32k.shift; + return ret; } static int __init omap_init_clocksource_32k(void)
After my OMAP3 board has been running for a while, I'm seeing weird latency traces like this: sh-1574 0d.h2 153us : do_timer (tick_do_update_jiffies64) sh-1574 0d.h2 153us : update_wall_time (do_timer) sh-1574 0d.h2 153us!: omap_32k_read (update_wall_time) sh-1574 0d.h2 1883us : update_xtime_cache (update_wall_time) sh-1574 0d.h2 1883us : clocksource_get_next (update_wall_time) sh-1574 0d.h2 1883us+: _spin_lock_irqsave (clocksource_get_next) and after a while: sh-17818 0d.h3 153us : do_timer (tick_do_update_jiffies64) sh-17818 0d.h3 153us : update_wall_time (do_timer) sh-17818 0d.h3 153us!: omap_32k_read (update_wall_time) sh-17818 0d.h3 1915us : update_xtime_cache (update_wall_time) sh-17818 0d.h3 1915us+: clocksource_get_next (update_wall_time) sh-17818 0d.h3 1945us : _spin_lock_irqsave (clocksource_get_next) Turns out that sched_clock() is using cyc2ns(), which returns NTP adjusted time. The sched_clock() frequency should not be adjusted. The patch deletes omap_32k_ticks_to_nsecs() and rewrites sched_clock() to do the conversion using the constant multiplier. Signed-off-by: Aaro Koskinen <Aaro.Koskinen@nokia.com> --- arch/arm/plat-omap/common.c | 14 +++++--------- 1 files changed, 5 insertions(+), 9 deletions(-)