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Subject[PATCH v1 07/10] sched/fair: Remove useless 64-bit to 32-bit variable conversion
Date
In __decay_sum(), the 64-bit to 32-bit variable conversion makes no
performance nor correctness use.

Minor cleanup and no functionality change.

Signed-off-by: Yuyang Du <yuyang.du@intel.com>
---
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
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