On 21 January 2011 17:44, Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote: > On Fri, Jan 21, 2011 at 09:43:18AM +0100, Vincent Guittot wrote: >> On 20 January 2011 17:11, Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote: >> > On Thu, Jan 20, 2011 at 09:25:54AM +0100, Vincent Guittot wrote: >> >> Please find below a new proposal for adding trace events for cpu hotplug. >> >> The goal is to measure the latency of each part (kernel, architecture) >> >> and also to trace the cpu hotplug activity with other power events. I >> >> have tested these traces events on an arm platform. >> >> >> >> Changes since previous version: >> >> -Use cpu_hotplug for trace name >> >> -Define traces for kernel core and arch parts only >> >> -Use DECLARE_EVENT_CLASS and DEFINE_EVENT >> >> -Use proper indentation >> >> >> >> Subject: [PATCH] cpu hotplug tracepoint >> >> >> >> this patch adds new events for cpu hotplug tracing >> >> * plug/unplug sequence >> >> * core and architecture latency measurements >> >> >> >> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> >> >> --- >> >> include/trace/events/cpu_hotplug.h | 117 ++++++++++++++++++++++++++++++++++++ >> > >> > Note we can't apply new tracepoints if they are not inserted in the code. >> >> I agree, i just want to have 1st feedbacks on the tracepoint interface >> before providing a patch which inserts the trace in the code. >> >> > >> >> +DEFINE_EVENT(cpu_hotplug, cpu_hotplug_arch_wait_die_start, >> >> + >> >> + TP_PROTO(unsigned int cpuid), >> >> + >> >> + TP_ARGS(cpuid) >> >> +); >> >> + >> >> +DEFINE_EVENT(cpu_hotplug, cpu_hotplug_arch_wait_die_end, >> >> + >> >> + TP_PROTO(unsigned int cpuid), >> >> + >> >> + TP_ARGS(cpuid) >> >> +); >> > >> > What is wait die, compared to die for example? >> > >> >> The arch_wait_die is used to trace the process which waits for the cpu >> to die (__cpu_die) and the arch_die is used to trace when the cpu dies >> (cpu_die) > > I still can't find the difference. > > Having: > > trace_cpu_hotplug_arch_die_start(cpu) > __cpu_die(); > trace_cpu_hotplug_arch_die_end(cpu) > > Is not enough to get both the information that a cpu dies > and the time took to do so? > it's quite interesting to trace the cpu_die function because the cpu really dies in this one. The __cpu_die function can't return if the cpu fails to die in the very last step and then wake up. But this could be detected with some cpu_die traces. for a normal use case we have something like : cpu 0 enters __cpu_die cpu 1 enters cpu_die cpu1 acks that it is going to died cpu0 returns from __cpu_die if the cpu 1 fails to die at the very last step, we could have: cpu 0 enters __cpu_die cpu 1 enters cpu_idle --> cpu_die cpu1 leaves cpu_die because of some issues and comes back into cpu_idle. cpu0 returns from __cpu_die after a timeout or an error ack Then, cpu_die traces can be used with power traces for profiling the cpu power state. May be, the power.h trace file is a better place for the cpu_die traces ? -- To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
