Re: [PATCH v1 0/2] perf stat: Support --all-kernel and --all-user

[Jin, Yao]

On 10/10/2019 8:33 PM, Arnaldo Carvalho de Melo wrote:
> Em Thu, Oct 10, 2019 at 04:33:57PM +0800, Jin, Yao escreveu:
> > On 10/10/2019 4:00 PM, Jiri Olsa wrote:
> > > On Thu, Oct 10, 2019 at 02:46:36PM +0800, Jin, Yao wrote:
> > > > On 10/1/2019 10:17 AM, Andi Kleen wrote:
> > > > > > > I think it's useful. Makes it easy to do kernel/user break downs.
> > > > > > > perf record should support the same.
> > > > > >
> > > > > > Don't we have this already with:
> > > > > >
> > > > > > [root@quaco ~]# perf stat -e cycles:u,instructions:u,cycles:k,instructions:k -a -- sleep 1
> > > > >
> > > > > This only works for simple cases. Try it for --topdown or multiple -M metrics.
> > > > >
> > > > > -Andi
> > > >
> > > > Hi Arnaldo, Jiri,
> > > >
> > > > We think it should be very useful if --all-user / --all-kernel can be
> > > > specified together, so that we can get a break down between user and kernel
> > > > easily.
> > > >
> > > > But yes, the patches for supporting this new semantics is much complicated
> > > > than the patch which just follows original perf-record behavior. I fully
> > > > understand this concern.
> > > >
> > > > So if this new semantics can be accepted, that would be very good. But if
> > > > you think the new semantics is too complicated, I'm also fine for posting a
> > > > new patch which just follows the perf-record behavior.
> > >
> > > I still need to think a bit more about this.. did you consider
> > > other options like cloning of the perf_evlist/perf_evsel and
> > > changing just the exclude* bits? might be event worse actualy ;-)
> >
> > That should be another approach, but it might be a bit more complicated than
> > just appending ":u"/":k" modifiers to the event name string.
> >
> > > or maybe if we add modifier we could add extra events/groups
> > > within the parser.. like:
> > >
> > >     "{cycles,instructions}:A,{cache-misses,cache-references}:A,cycles:A"
> > >
> > > but that might be still more complicated then what you did
> >
> > Yes agree.
> >
> > > also please add the perf record changes so we have same code
> > > and logic for both if we are going to change it
>   
> > If this new semantics can be accepted, I'd like to add perf record
> > supporting as well. :)
>
> Changes in semantics should be avoided, when we add an option already
> present in some other tool, we should strive to keep the semantics, so
> that people can reuse their knowledge and just switch tools to go from
> sampling to counting, say.

Yes, that makes sense. We need to try our best to keep the original 
semantics. I will post a patch for perf-stat which just follows the 
semantics in perf-record.

> So if at all possible, and without having really looked deep in this
> specific case, I would prefer that new semantics come with a new syntax,
> would that be possible?

Yes, that's possible. Maybe we can use a new option for automatically 
adding two copies of the events (one copy for user and the other copy 
for kernel). The option something like "--all-space"?

Thanks
Jin Yao

> - Arnaldo
>   



> > Another difficulty for the new semantics is we need to create user and
> > kernel stat type in runtime_stat rblist (see patch "perf stat: Support
> > topdown with --all-kernel/--all-user"). That has to bring extra complexity.
> >
> > Thanks
> > Jin Yao
> >
> > > jirka