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Commit e213b1bc authored by Joonwoo Park's avatar Joonwoo Park Committed by Matt Wagantall
Browse files

sched: fix rounding error on scaled execution time calculation 



It's found that the scaled execution time can be less than its actual time
due to rounding errors.  The HMP scheduler accumulates scaled execution
time of tasks to determine if tasks are in need of up-migration.  But the
rounding error prevents the HMP scheduler from accumulating 100% load which
prevents us from ever reaching an up-migrate of 100%.
Fix rounding error by rounding quotient up.

CRs-fixed: 759041
Change-Id: Ie4d9693593cc3053a292a29078aa56e6de8a2d52
Signed-off-by: default avatarJoonwoo Park <joonwoop@codeaurora.org>
parent de9bc1fb

kernel/sched/core.c

+9 −4
Original line number Diff line number Diff line
@@ -1286,8 +1286,12 @@ static inline u64 scale_exec_time(u64 delta, struct rq *rq) 
		      rq->max_freq < rq->max_possible_freq)))

		cur_freq = rq->max_possible_freq;



	delta = div64_u64(delta  * cur_freq, max_possible_freq);

	sf = (rq->efficiency * 1024) / max_possible_efficiency;

	/* round up div64 */

	delta = div64_u64(delta * cur_freq + max_possible_freq - 1,

			  max_possible_freq);



	sf = DIV_ROUND_UP(rq->efficiency * 1024, max_possible_efficiency);



	delta *= sf;

	delta >>= 10;
@@ -2330,7 +2334,8 @@ unsigned long capacity_scale_cpu_freq(int cpu) 
 */

static inline unsigned long load_scale_cpu_efficiency(int cpu)

{

	return (1024 * max_possible_efficiency) / cpu_rq(cpu)->efficiency;

	return DIV_ROUND_UP(1024 * max_possible_efficiency,

			    cpu_rq(cpu)->efficiency);

}



/*
@@ -2340,7 +2345,7 @@ static inline unsigned long load_scale_cpu_efficiency(int cpu) 
 */

static inline unsigned long load_scale_cpu_freq(int cpu)

{

	return (1024 * max_possible_freq) / cpu_rq(cpu)->max_freq;

	return DIV_ROUND_UP(1024 * max_possible_freq, cpu_rq(cpu)->max_freq);

}



static int compute_capacity(int cpu)