Re: [PATCH 1/1] KVM: halt_polling: provide a way to qualify wakeups during poll

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 05/03/2016 05:03 PM, Radim Krčmář wrote:
> 2016-05-03 14:56+0200, Cornelia Huck:
>> On Tue,  3 May 2016 14:37:21 +0200
>> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
>>> diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
>>> index aa69253..92e6fd6 100644
>>> --- a/include/trace/events/kvm.h
>>> +++ b/include/trace/events/kvm.h
>>> @@ -38,22 +38,25 @@ TRACE_EVENT(kvm_userspace_exit,
>>>  );
>>>
>>>  TRACE_EVENT(kvm_vcpu_wakeup,
>>> -	    TP_PROTO(__u64 ns, bool waited),
>>> -	    TP_ARGS(ns, waited),
>>> +	    TP_PROTO(__u64 ns, bool waited, bool tuned),
>>> +	    TP_ARGS(ns, waited, tuned),
>>>
>>>  	TP_STRUCT__entry(
>>>  		__field(	__u64,		ns		)
>>>  		__field(	bool,		waited		)
>>> +		__field(	bool,		tuned		)
>>>  	),
>>>
>>>  	TP_fast_assign(
>>>  		__entry->ns		= ns;
>>>  		__entry->waited		= waited;
>>> +		__entry->tuned		= tuned;
>>>  	),
>>>
>>> -	TP_printk("%s time %lld ns",
>>> +	TP_printk("%s time %lld ns, polling %s",
>>>  		  __entry->waited ? "wait" : "poll",
>>> -		  __entry->ns)
>>> +		  __entry->ns,
>>> +		  __entry->tuned ? "changed" : "unchanged")
>>
>> I think "changed"/"unchanged" is a bit misleading here, as we do adjust
>> the intervall if we had an invalid poll... but it's hard to find a
>> suitable text here.
>>
>> Just print "poll interval tuned" if we were (a) polling to begin with,
>> (b) the poll was valid and (c) the interval was actually changed and
>> print "invalid poll" if that's what happened? Or is that overkill?
> 
> Just renaming to valid/invalid is fine, IMO, the state of polling is
> static and interval change can be read from other traces.
> 
> I think that having "no_tuning" counter, "unchanged" trace and "invalid"
> in source names obscures the logical connection;  doesn't "invalid" fit
> them all?
> 

Yes, will change tracing into 
__entry->valid ? "valid" : "invalid")
and halt_poll_no_tuning --> halt_poll_invalid

That seems to be in line with the remaining parts of the patch.

Christian