| Message ID | 1510076133-18139-3-git-send-email-pprakash@codeaurora.org (mailing list archive) |
|---|---|
| State | Deferred, archived |
| Headers | show |
On 07/11/17 17:35, Prashanth Prakash wrote: > CPU_PM_CPU_IDLE_ENTER_RETENTION skips calling cpu_pm_enter() and > cpu_pm_exit(). By not calling cpu_pm functions in idle entry/exit > paths we can reduce the latency involved in entering and exiting > the low power idle state. > > On ARM64 based Qualcomm server platform we measured below overhead > for calling cpu_pm_enter and cpu_pm_exit for retention states. > > workload: stress --hdd #CPUs --hdd-bytes 32M -t 30 > Average overhead of cpu_pm_enter - 1.2us > Average overhead of cpu_pm_exit - 3.1us > > Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org> > --- > arch/arm64/kernel/cpuidle.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/cpuidle.c b/arch/arm64/kernel/cpuidle.c > index fd69108..f2d1381 100644 > --- a/arch/arm64/kernel/cpuidle.c > +++ b/arch/arm64/kernel/cpuidle.c > @@ -47,6 +47,8 @@ int arm_cpuidle_suspend(int index) > > #include <acpi/processor.h> > > +#define ARM64_LPI_IS_RETENTION_STATE(arch_flags) (!(arch_flags)) > + Ideally we could cater both ACPI LPI and DT using PSCI parameters. No ? Just thinking it out loud as I see no reason to restrict this just to ACPI LPIs.
On 08/11/17 14:27, Sudeep Holla wrote: > > > On 07/11/17 17:35, Prashanth Prakash wrote: >> CPU_PM_CPU_IDLE_ENTER_RETENTION skips calling cpu_pm_enter() and >> cpu_pm_exit(). By not calling cpu_pm functions in idle entry/exit >> paths we can reduce the latency involved in entering and exiting >> the low power idle state. >> >> On ARM64 based Qualcomm server platform we measured below overhead >> for calling cpu_pm_enter and cpu_pm_exit for retention states. >> >> workload: stress --hdd #CPUs --hdd-bytes 32M -t 30 >> Average overhead of cpu_pm_enter - 1.2us >> Average overhead of cpu_pm_exit - 3.1us >> >> Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org> >> --- >> arch/arm64/kernel/cpuidle.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/kernel/cpuidle.c b/arch/arm64/kernel/cpuidle.c >> index fd69108..f2d1381 100644 >> --- a/arch/arm64/kernel/cpuidle.c >> +++ b/arch/arm64/kernel/cpuidle.c >> @@ -47,6 +47,8 @@ int arm_cpuidle_suspend(int index) >> >> #include <acpi/processor.h> >> >> +#define ARM64_LPI_IS_RETENTION_STATE(arch_flags) (!(arch_flags)) >> + > > Ideally we could cater both ACPI LPI and DT using PSCI parameters. No ? > Just thinking it out loud as I see no reason to restrict this just to > ACPI LPIs. > Just to add, after chatting with Lorenzo, I see PSCI covers only core states but that then leads to my question in the other patch: do we need partial state save/restore ever ? If not, then we can still use PSCI flag in both DT and ACPI.
diff --git a/arch/arm64/kernel/cpuidle.c b/arch/arm64/kernel/cpuidle.c index fd69108..f2d1381 100644 --- a/arch/arm64/kernel/cpuidle.c +++ b/arch/arm64/kernel/cpuidle.c @@ -47,6 +47,8 @@ int arm_cpuidle_suspend(int index) #include <acpi/processor.h> +#define ARM64_LPI_IS_RETENTION_STATE(arch_flags) (!(arch_flags)) + int acpi_processor_ffh_lpi_probe(unsigned int cpu) { return arm_cpuidle_init(cpu); @@ -54,6 +56,10 @@ int acpi_processor_ffh_lpi_probe(unsigned int cpu) int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi) { - return CPU_PM_CPU_IDLE_ENTER(arm_cpuidle_suspend, lpi->index); + if (ARM64_LPI_IS_RETENTION_STATE(lpi->arch_flags)) + return CPU_PM_CPU_IDLE_ENTER_RETENTION(arm_cpuidle_suspend, + lpi->index); + else + return CPU_PM_CPU_IDLE_ENTER(arm_cpuidle_suspend, lpi->index); } #endif
CPU_PM_CPU_IDLE_ENTER_RETENTION skips calling cpu_pm_enter() and cpu_pm_exit(). By not calling cpu_pm functions in idle entry/exit paths we can reduce the latency involved in entering and exiting the low power idle state. On ARM64 based Qualcomm server platform we measured below overhead for calling cpu_pm_enter and cpu_pm_exit for retention states. workload: stress --hdd #CPUs --hdd-bytes 32M -t 30 Average overhead of cpu_pm_enter - 1.2us Average overhead of cpu_pm_exit - 3.1us Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org> --- arch/arm64/kernel/cpuidle.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)