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sched/fair: add boosted CPU usage

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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: Patrick Bellasi <patrick.bellasi@arm.com>
This commit is contained in:
Patrick Bellasi
2015-06-26 09:55:06 +01:00
committed by Leo Yan
parent 6ed2714501
commit 07e22949de
1 changed files with 32 additions and 1 deletions
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33
kernel/sched/fair.c
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@@ -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.