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| author | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2019-11-07 17:25:12 +0300 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2019-11-11 23:56:07 +0300 |
| commit | c1d51f684c72b5eb2aecbbd47be3a2977a2dc903 (patch) | |
| tree | 4e929d24f9033246e46d08ebf2157d0d438941a1 /drivers/cpuidle/governor.c | |
| parent | 99e98d3fb1008ef7416e16a1fd355cb73a253502 (diff) | |
| download | linux-c1d51f684c72b5eb2aecbbd47be3a2977a2dc903.tar.xz | |
cpuidle: Use nanoseconds as the unit of time
Currently, the cpuidle subsystem uses microseconds as the unit of
time which (among other things) causes the idle loop to incur some
integer division overhead for no clear benefit.
In order to allow cpuidle to measure time in nanoseconds, add two
new fields, exit_latency_ns and target_residency_ns, to represent the
exit latency and target residency of an idle state in nanoseconds,
respectively, to struct cpuidle_state and initialize them with the
help of the corresponding values in microseconds provided by drivers.
Additionally, change cpuidle_governor_latency_req() to return the
idle state exit latency constraint in nanoseconds.
Also meeasure idle state residency (last_residency_ns in struct
cpuidle_device and time_ns in struct cpuidle_driver) in nanoseconds
and update the cpuidle core and governors accordingly.
However, the menu governor still computes typical intervals in
microseconds to avoid integer overflows.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Doug Smythies <dsmythies@telus.net>
Tested-by: Doug Smythies <dsmythies@telus.net>
Diffstat (limited to 'drivers/cpuidle/governor.c')
| -rw-r--r-- | drivers/cpuidle/governor.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/cpuidle/governor.c b/drivers/cpuidle/governor.c index e9801f26c732..e48271e117a3 100644 --- a/drivers/cpuidle/governor.c +++ b/drivers/cpuidle/governor.c @@ -107,11 +107,14 @@ int cpuidle_register_governor(struct cpuidle_governor *gov) * cpuidle_governor_latency_req - Compute a latency constraint for CPU * @cpu: Target CPU */ -int cpuidle_governor_latency_req(unsigned int cpu) +s64 cpuidle_governor_latency_req(unsigned int cpu) { int global_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY); struct device *device = get_cpu_device(cpu); int device_req = dev_pm_qos_raw_resume_latency(device); - return device_req < global_req ? device_req : global_req; + if (device_req > global_req) + device_req = global_req; + + return (s64)device_req * NSEC_PER_USEC; } |