Messages in this thread | | | Date | Wed, 16 Sep 2015 17:16:05 +0100 | From | Lorenzo Pieralisi <> | Subject | Re: [PATCH] arm64: add cpu_idle tracepoints to arch_cpu_idle |
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On Wed, Sep 16, 2015 at 04:11:05PM +0100, Jisheng Zhang wrote: > Dear Lorenzo, > > On Wed, 16 Sep 2015 22:53:12 +0800 > Jisheng Zhang <jszhang@marvell.com> wrote: > > > Dear Lorenzo, > > > > On Wed, 16 Sep 2015 15:47:38 +0100 > > Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: > > > > > On Wed, Sep 16, 2015 at 03:23:21PM +0100, Jisheng Zhang wrote: > > > > Currently, if cpuidle is disabled or not supported, powertop reports > > > > zero wakeups and zero events. This is due to the cpu_idle tracepoints > > > > are missing. > > > > > > > > This patch is to make cpu_idle tracepoints always available even if > > > > cpuidle is disabled or not supported. > > > > > > > > Signed-off-by: Jisheng Zhang <jszhang@marvell.com> > > > > > > Is there a reason why this code cannot be moved to the generic idle loop ? > > > > Do you mean the cpu_idle_loop() in kernel/sched/idle.c? To be honest, I > > Maybe I know now. we need to trace different idle level, for example: > > WFI idle: trace_cpu_idle_rcuidle(1, ...); > > deeper idle: trace_cpu_idle_rcuidle(2, ...); > > Usually, the first argument of trace_cpu_idle_rcuidle() equals to the index > of the idle level. > > so generic idle loop is not a good candidate.
You are adding a trace for tracing state 1 (ie default idle state), called from arch_cpu_idle(), which is the default idle call when the CPUidle framework is not available, so I suggested moving the traces you add to arm/arm64 arch_cpu_idle() calls to kernel/sched/idle.c (see default_idle_call()) instead of patching architecture code.
I think you can't do that because on x86 calling arch_cpu_idle() does not always mean entering idle state index 1 if I read the code correctly (in particular the mwait based implementation - mwait_idle()).
So never mind, patch is fine (on arm64, on arm you should be careful because some arm_pm_idle implementations trace state 1 already - see omap3_pm_idle and if you add traces to arch_cpu_idle you should remove the traces from mach implementations).
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
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