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| author | Syed Rameez Mustafa <rameezmustafa@codeaurora.org> | 2015-02-20 17:09:41 -0800 |
|---|---|---|
| committer | David Keitel <dkeitel@codeaurora.org> | 2016-03-23 20:01:52 -0700 |
| commit | f0ddb64b10d12a964eb8d70a9547e39f3106d250 (patch) | |
| tree | 2b49c6e2e2020d792ce2ce017d712060627833a3 /kernel/sched/sched.h | |
| parent | b55f87849bb1bd573410ef1a1f491f2a418ed664 (diff) | |
sched: Update max_capacity when an entire cluster is hotplugged
When an entire cluster is hotplugged, the scheduler's notion of
max_capacity can get outdated. This introduces the following
inefficiencies in behavior:
* task_will_fit() does not return true on all tasks. Consequently
all big tasks go through fallback CPU selection logic skipping
C-state and power checks in select_best_cpu().
* During boost, migration_needed() return true unnecessarily
causing an avoidable rerun of select_best_cpu().
* An unnecessary kick is sent to all little CPUs when boost is set.
* An opportunity for early bailout from nohz_kick_needed() is lost.
Start handling CPUFREQ_REMOVE_POLICY in the policy notifier callback
which indicates the last CPU in a cluster being hotplugged out. Also
modify update_min_max_capacity() to only iterate through online CPUs
instead of possible CPUs. While we can't guarantee the integrity of
the cpu_online_mask in the notifier callback, the scheduler will fix
up all state soon after any changes to the online mask.
The change does have one side effect; early termination from the
notifier callback when min_max_freq or max_possible_freq remain
unchanged is no longer possible. This is because when the last CPU
in a cluster is hot removed, only max_capacity is updated without
affecting min_max_freq or max_possible_freq. Therefore, when the
first CPU in the same cluster gets hot added at a later point
max_capacity must once again be recomputed despite there being no
change in min_max_freq or max_possible_freq.
Change-Id: I9a1256b5c2cd6fcddd85b069faf5e2ace177e122
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>
Diffstat (limited to 'kernel/sched/sched.h')
| -rw-r--r-- | kernel/sched/sched.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index d897c967bb87..1d675545817e 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -990,6 +990,7 @@ extern unsigned int min_possible_efficiency; extern unsigned int max_capacity; extern unsigned int min_capacity; extern unsigned int max_load_scale_factor; +extern unsigned int max_possible_capacity; extern unsigned long capacity_scale_cpu_efficiency(int cpu); extern unsigned long capacity_scale_cpu_freq(int cpu); extern unsigned int sched_mostly_idle_load; |