Messages in this thread | | | Date | Tue, 21 Jan 2014 14:49:39 +0800 | From | Michael wang <> | Subject | Re: [RFC PATCH 1/2] sched/update_avg: avoid negative time |
| |
Hi, Alex
On 01/21/2014 01:33 PM, Alex Shi wrote: > rq->avg_idle try to reflect the average idle time between the cpu idle > and first wakeup. But in the function, it maybe get a negative value > if old avg_idle is too small. Then this negative value will be double > counted in next time calculation. Guess that is not the original purpose, > so recalibrate it to zero. > > Signed-off-by: Alex Shi <alex.shi@linaro.org> > --- > kernel/sched/core.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 30eb011..af9121c6 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1358,6 +1358,9 @@ static void update_avg(u64 *avg, u64 sample) > { > s64 diff = sample - *avg; > *avg += diff >> 3; > + > + if (*avg < 0) > + *avg = 0;
This seems like won't happen...
if 'diff' is negative, it's absolute value won't bigger than '*avg', not to mention we only use 1/8 of it.
Regards, Michael Wang
> } > #endif >
| |