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Commit 07e22949 authored by Patrick Bellasi's avatar Patrick Bellasi Committed by Leo Yan
Browse files

sched/fair: add boosted CPU usage 



The CPU usage signal is used by the scheduler as an estimation of the
overall bandwidth currently allocated on a CPU. When SchedDVFS is in
use, this signal affects the selection of the operating points (OPP)
required to accommodate all the workload allocated in a CPU.
A convenient way to boost the performance of tasks running on a CPU,
which is also little intrusive, is to boost the CPU usage signal each
time it is used to select an OPP.

This patch introduces a new function:
  get_boosted_cpu_usage(cpu)
to return a boosted value for the usage of a specified CPU.
The margin added to the original usage is:
  1. computed based on the "boosting strategy" in use
  2. proportional to the system-wide boost value defined by provided
     user-space interface

The boosted signal is used by SchedDVFS (transparently) each time it
requires to get an estimation of the capacity required for a CPU.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarPatrick Bellasi <patrick.bellasi@arm.com>
parent 6ed27145

kernel/sched/fair.c

+32 −1
Original line number Diff line number Diff line
@@ -4144,6 +4144,8 @@ static inline void hrtick_update(struct rq *rq) 
}

#endif



static inline unsigned long boosted_cpu_util(int cpu);



static void update_capacity_of(int cpu)

{

	unsigned long req_cap;
@@ -4152,7 +4154,8 @@ static void update_capacity_of(int cpu) 
		return;



	/* Convert scale-invariant capacity to cpu. */

	req_cap = cpu_util(cpu) * SCHED_CAPACITY_SCALE / capacity_orig_of(cpu);

	req_cap = boosted_cpu_util(cpu);

	req_cap = req_cap * SCHED_CAPACITY_SCALE / capacity_orig_of(cpu);

	set_cfs_cpu_capacity(cpu, true, req_cap);

}
@@ -5110,8 +5113,36 @@ schedtune_margin(unsigned long signal, unsigned long boost) 
	return margin;

}



static inline unsigned int

schedtune_cpu_margin(unsigned long util)

{

	unsigned int boost = get_sysctl_sched_cfs_boost();



	if (boost == 0)

		return 0;



	return schedtune_margin(util, boost);

}



#else /* CONFIG_SCHED_TUNE */



static inline unsigned int

schedtune_cpu_margin(unsigned long util)

{

	return 0;

}



#endif /* CONFIG_SCHED_TUNE */



static inline unsigned long

boosted_cpu_util(int cpu)

{

	unsigned long util = cpu_util(cpu);

	unsigned long margin = schedtune_cpu_margin(util);



	return util + margin;

}



/*

 * find_idlest_group finds and returns the least busy CPU group within the

 * domain.