linux-kernel - Re: [PATCH] perf, tools, script: Allow adding and removing fields

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Date:   Thu, 8 Jun 2017 19:52:43 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Milian Wolff <milian.wolff@...b.com>
Cc:     Andi Kleen <andi@...stfloor.org>, acme@...nel.org,
        jolsa@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf, tools, script: Allow adding and removing fields

On Thu, Jun 08, 2017 at 02:59:58PM +0200, Milian Wolff wrote:
> But I notice that this functionality is missing in other places too. Most 
> notably, I would like to be able to configure `perf stat` in a similar way. 
> Such that one could do:
> 
> perf stat -e +cache-misses
> 
> Instead of
> 
> perf stat -e <whatever the defaults are>,cache-misses

The defaults are not great, so I'm not sure that is super useful.

It's probably better to assemble reasonable groups, perhaps
with groups of metrics.

> But I cannot do:
> 
> $ perf record -e "topdown-*" ls
> event syntax error: 'topdown-*'

That's actually good because the current topdown events are not useful to sample

Usually you need to have at least some idea about the events you're collecting,
and also for non trivial collections you need groups to get good results.

I've been thinking about adding MetricGroups to the json files, that
would allow to assemble reasonable groups. But it still wouldn't be wildcard.

For a few things wildcards are useful, e.g. I implemented it recently
for PMUs so that uncore PMUs are easier to handle.

-Andi