On 4 June 2014 19:30, Doug Anderson <[email protected]> wrote: > From: Mandeep Singh Baines <[email protected]> > > Saves one register read. Note that the upper count only changes every > ~178 seconds with a 24MHz source clock, so it's likely it hasn't > changed from call to call.
Hi Doug, Have you checked that the time saved in using a 32bits counter instead of a 64bits one is not lost in the handle of the wrap of sched_clock which occurs every 178s instead of never ? sched_clock_poll function will be called every 178s Regards, Vincent > > Before: 1323852 us for 1000000 gettimeofday in userspace > After: 1173084 us for 1000000 gettimeofday in userspace > > Note that even with this change the CPU is in exynos_frc_read() more > than 2% of the time in real world profiles of ChromeOS. That > indicates that it's important to optimize. > > Signed-off-by: Mandeep Singh Baines <[email protected]> > Signed-off-by: Andrew Bresticker <[email protected]> > Signed-off-by: Doug Anderson <[email protected]> > --- > drivers/clocksource/exynos_mct.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/clocksource/exynos_mct.c > b/drivers/clocksource/exynos_mct.c > index ba3a683..7cbe4aa 100644 > --- a/drivers/clocksource/exynos_mct.c > +++ b/drivers/clocksource/exynos_mct.c > @@ -167,8 +167,8 @@ static void exynos4_mct_frc_start(u32 hi, u32 lo) > > static inline cycle_t notrace _exynos4_frc_read(void) > { > - unsigned int lo, hi; > - u32 hi2 = __raw_readl(reg_base + EXYNOS4_MCT_G_CNT_U); > + u32 lo, hi; > + static u32 hi2; > > do { > hi = hi2; > -- > 2.0.0.526.g5318336 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
