Hi Leo, On 5 August 2016 at 08:34, Leo Yan <leo....@linaro.org> wrote: > > In current code, decay_load() will consider to set load value to zero > after passing 32*64 ms. So this means max_load * (0.5^64) ~= 0. > > Kernel can support maximum number of processes and threads to 2^29 and > set task with highest priority with nice=-20 (weight = 88761). So in > worst case, one CPU may have maximum load value is: > > max_load = 2^29 * 88761 < 2^46 > > In theory after pass 46 periods we can ensure load value will be decayed > to zero. So this patch is to change maximum periods from 64 to 48. > > Signed-off-by: Leo Yan <leo....@linaro.org> > --- > kernel/sched/fair.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index e342159..55cb134 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2622,7 +2622,7 @@ static __always_inline u64 decay_load(u64 val, u64 n) > > if (!n) > return val; > - else if (unlikely(n > LOAD_AVG_PERIOD * 63)) > + else if (unlikely(n > LOAD_AVG_PERIOD * 47))
In the equation above, you use 46 then you mentioned : "change maximum periods from 64 to 48." and finally you use 47. > return 0; > > /* after bounds checking we can collapse to 32-bit */ > -- > 1.9.1 >
