linux-kernel - Re: [RFC PATCH v3 00/37] perf tools: introduce 'perf bpf' command to load eBPF programs.

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Date:	Tue, 19 May 2015 19:05:29 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Alexei Starovoitov <ast@...mgrid.com>
Cc:	Namhyung Kim <namhyung@...nel.org>, Wang Nan <wangnan0@...wei.com>,
	paulus@...ba.org, a.p.zijlstra@...llo.nl, mingo@...hat.com,
	jolsa@...nel.org, dsahern@...il.com, daniel@...earbox.net,
	brendan.d.gregg@...il.com, masami.hiramatsu.pt@...achi.com,
	lizefan@...wei.com, linux-kernel@...r.kernel.org, pi3orama@....com
Subject: Re: [RFC PATCH v3 00/37] perf tools: introduce 'perf bpf' command to
 load eBPF programs.

Em Tue, May 19, 2015 at 02:42:11PM -0700, Alexei Starovoitov escreveu:
> On 5/19/15 2:10 PM, Arnaldo Carvalho de Melo wrote:
> >
> >This all should use infrastructure in perf for symbol resolving,
> >callcahins, etc.
> 
> yes. 100%
> 
> >Right, but if we do a:
> >
> >perf script -i perf.data bpf_file.c
> >
> >Then there would be a short circuit effect of just doing the
> >aggregation and/or reporting.

Ok, can you point me to this bpf_file.c, an example? So that we can talk
about the parts of it that would be short circuited when not loading the
bpf_file.o, etc.
 
> That can work, but I don't see why I would use bpf for
> scripting on top of perf.data. If trace is already collected,
> the existing perl/python scripts will work fine.

> >Well, we could have a tee like mode where perf.data file could be
> >generated so that we could run it again after doing some change on the
> >aggregation code, so that we wouldn't have to re-run the data collection
> >parts, that could be about some condition hard to capture, etc.
> 
> true, but again I don't think in such scenario you'd need bpf.
> bpf is needed when the number of events is huge and the user
> needs to aggregate/process them in-kernel.
> 
> >>I guess I'm saying let's not get too much ahead of ourselves ;)
> >
> >No problem, but then we need to talk at this moment not to add new stuff
> >that we think should not be added, like 'perf bpf' :-)
> 
> ahh, that's where you going :) Sure. I don't mind avoiding that

:-) If there is no need, why add a new command? I.e. if all that is
wanted can be used by integrating eBPF into existing commands, that
could be best.

> unbearable abbreviation if we can :)

:-)

> 'perf script file.[oc]' command line works for me.

- Arnaldo
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