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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-11-07 17:25:12 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-11-11 23:56:07 +0300
commitc1d51f684c72b5eb2aecbbd47be3a2977a2dc903 (patch)
tree4e929d24f9033246e46d08ebf2157d0d438941a1 /drivers/cpuidle/governor.c
parent99e98d3fb1008ef7416e16a1fd355cb73a253502 (diff)
downloadlinux-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.c7
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;
}