Re: [RFC] perf evlist: Warn if event group has mixed sw/hw events

[Alexander Shishkin]

Andi Kleen <ak@xxxxxxxxxxxxxxx> writes:

> On Mon, Oct 26, 2020 at 11:19:37PM +0900, Namhyung Kim wrote:
>> This patch just added a warning before running it.  I'd really want to
>> fix the kernel if possible but don't have a good idea.  Thoughts?
>
> The easiest fix would be some multi threading in perf stat opening, then then
> extra latencies could be mostly hidden. One thread per group would probably
> be overkill, but just a few threads would lower the penalty significantly.
>
> I think that would be better than this patch and it's likely not that much
> more complicated, as this is already a lot of code.
>
>> +{
>> +	const char *known_sw_pmu[] = {
>> +		"software", "tracepoint", "breakpoint", "kprobe", "uprobe", "msr"
>
> That's a non scalable approach. New pmus get added regularly. It would be better to
> indicate this in a generic way from the kernel.

That, and also, intel_pt is a software PMU and a few of its features
depend on intel_pt/.../ being a group leader.

Regards,
--
Alex