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SubjectRe: [PATCH v2] cpuidle: haltpoll: Add trace points for guest_halt_poll_ns grow/shrink
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Hi Steven

> On May 26, 2022, at 1:02, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Mon, 23 May 2022 23:53:32 +0000
> Eiichi Tsukata <eiichi.tsukata@nutanix.com> wrote:
>
>> @@ -91,16 +95,17 @@ static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns)
>> val = guest_halt_poll_ns;
>>
>> dev->poll_limit_ns = val;
>> + trace_guest_halt_poll_ns_grow(smp_processor_id(), val, old);
>
> Why are you passing in smp_processor_id()?
>
>> } else if (block_ns > guest_halt_poll_ns &&
>> guest_halt_poll_allow_shrink) {
>> unsigned int shrink = guest_halt_poll_shrink;
>>
>> - val = dev->poll_limit_ns;
>> if (shrink == 0)
>> val = 0;
>> else
>> val /= shrink;
>> dev->poll_limit_ns = val;
>> + trace_guest_halt_poll_ns_shrink(smp_processor_id(), val, old);
>> }
>> }
>>
>> diff --git a/include/trace/events/power.h b/include/trace/events/power.h
>> index af5018aa9517..db065af9c3c0 100644
>> --- a/include/trace/events/power.h
>> +++ b/include/trace/events/power.h
>> @@ -500,6 +500,39 @@ DEFINE_EVENT(dev_pm_qos_request, dev_pm_qos_remove_request,
>>
>> TP_ARGS(name, type, new_value)
>> );
>> +
>> +TRACE_EVENT(guest_halt_poll_ns,
>> +
>> + TP_PROTO(bool grow, unsigned int cpu_id,
>> + unsigned int new, unsigned int old),
>> +
>> + TP_ARGS(grow, cpu_id, new, old),
>> +
>> + TP_STRUCT__entry(
>> + __field(bool, grow)
>> + __field(unsigned int, cpu_id)
>> + __field(unsigned int, new)
>> + __field(unsigned int, old)
>> + ),
>> +
>> + TP_fast_assign(
>> + __entry->grow = grow;
>> + __entry->cpu_id = cpu_id;
>
> You are wasting space to save the cpu_id, as the trace event already knows
> what CPU it occurred on.
>
> # echo 1 > events/sched/enable
> # cat trace
> # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
> # | | | ||||| | |
> systemd-1 [004] ..... 15.872715: ftrace_boot_snapshot: ** Boot snapshot taken **
> systemd-1 [001] ..... 22.555418: initcall_start: func=fuse_len_args+0x0/0x30 [fuse]
> systemd-1 [001] ..... 22.555425: initcall_finish: func=fuse_len_args+0x0/0x30 [fuse] ret=0
> modprobe-643 [006] ..... 26.737355: initcall_start: func=wmidev_evaluate_method+0x46/0x100 [wmi]
> modprobe-643 [006] ..... 26.742491: initcall_finish: func=wmidev_evaluate_method+0x46/0x100 [wmi] ret=0
>
> -- Steve

Thanks for your suggestion.
I added cpu_id as there is a similar precedent “trace_cpu_idle” but I think we can remove cpu_id.
Will fix it in v3.

Eiichi
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