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sched/{fair,tune}: use reciprocal_value to compute boost margin

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Change-Id: I493b07360c46eee0b72c2a046dab9ec6cb3427ef
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Srinath Sridharan <srinathsr@google.com>
This commit is contained in:
Patrick Bellasi 2016-10-13 17:31:24 +01:00 • committed by Andres Oportus
parent 41d9288e3e
commit 7b8577d94c
2 changed files with 9 additions and 17 deletions
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23
kernel/sched/fair.c
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@ -5805,6 +5805,8 @@ static bool cpu_overutilized(int cpu)
#ifdef CONFIG_SCHED_TUNE
struct reciprocal_value schedtune_spc_rdiv;
static long
schedtune_margin(unsigned long signal, long boost)
{
@ -5815,29 +5817,16 @@ schedtune_margin(unsigned long signal, long boost)
*
* The Boost (B) value is used to compute a Margin (M) which is
* proportional to the complement of the original Signal (S):
* M = B * (SCHED_LOAD_SCALE - S), if B is positive
* M = B * S, if B is negative
* M = B * (SCHED_CAPACITY_SCALE - S)
* The obtained M could be used by the caller to "boost" S.
*/
if (boost >= 0) {
margin = SCHED_LOAD_SCALE - signal;
margin = SCHED_CAPACITY_SCALE - signal;
margin *= boost;
} else
margin = -signal * boost;
/*
* Fast integer division by constant:
* Constant : (C) = 100
* Precision : 0.1% (P) = 0.1
* Reference : C * 100 / P (R) = 100000
*
* Thus:
* Shift bits : ceil(log(R,2)) (S) = 17
* Mult const : round(2^S/C) (M) = 1311
*
*
*/
margin *= 1311;
margin >>= 17;
margin = reciprocal_divide(margin, schedtune_spc_rdiv);
if (boost < 0)
margin *= -1;

3
kernel/sched/tune.c
View file

@ -17,6 +17,7 @@ static bool schedtune_initialized = false;
unsigned int sysctl_sched_cfs_boost __read_mostly;
extern struct reciprocal_value schedtune_spc_rdiv;
extern struct target_nrg schedtune_target_nrg;
/* Performance Boost region (B) threshold params */
@ -937,6 +938,8 @@ schedtune_init(void)
pr_info("schedtune: configured to support global boosting only\n");
#endif
schedtune_spc_rdiv = reciprocal_value(100);
return 0;
nodata: