On 10 August 2016 at 02:14, Yuyang Du <[email protected]> wrote: > In __decay_sum(), the 64-bit to 32-bit variable conversion makes no > performance nor correctness use.
Are you sure that there is no impact on 32bits system ? Even this will be mainly shift manipulation > > Minor cleanup and no functionality change. > > Signed-off-by: Yuyang Du <[email protected]> > --- > kernel/sched/fair.c | 13 ++++--------- > 1 file changed, 4 insertions(+), 9 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 283e2c2..eea3349 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2616,16 +2616,11 @@ static const u32 __accumulated_sum_N32[] = { > */ > static __always_inline u64 __decay_sum(u64 val, u64 n) > { > - unsigned int local_n; > - > if (!n) > return val; > else if (unlikely(n > SCHED_AVG_HALFLIFE * 63)) > return 0; > > - /* after bounds checking we can collapse to 32-bit */ > - local_n = n; > - > /* > * As y^HALFLIFE = 1/2, we can combine > * y^n = 1/2^(n/HALFLIFE) * y^(n%HALFLIFE) > @@ -2633,12 +2628,12 @@ static __always_inline u64 __decay_sum(u64 val, u64 n) > * > * To achieve constant time __decay_load. > */ > - if (unlikely(local_n >= SCHED_AVG_HALFLIFE)) { > - val >>= local_n / SCHED_AVG_HALFLIFE; > - local_n %= SCHED_AVG_HALFLIFE; > + if (unlikely(n >= SCHED_AVG_HALFLIFE)) { > + val >>= n / SCHED_AVG_HALFLIFE; > + n %= SCHED_AVG_HALFLIFE; > } > > - val = mul_u64_u32_shr(val, __decay_inv_multiply_N[local_n], 32); > + val = mul_u64_u32_shr(val, __decay_inv_multiply_N[n], 32); > return val; > } > > -- > 1.7.9.5 >
