linux-kernel - Re: [PATCH] perf tools: Add sample types for bpf-output event

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Message-ID: <20160401151930.GB9494@redhat.com>
Date:	Fri, 1 Apr 2016 12:19:30 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Wang Nan <wangnan0@...wei.com>, linux-kernel@...r.kernel.org,
	pi3orama@....com, Adrian Hunter <adrian.hunter@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
	Milian Wolff <milian.wolff@...b.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Brendan Gregg <brendan.d.gregg@...il.com>
Subject: Re: [PATCH] perf tools: Add sample types for bpf-output event

Em Fri, Apr 01, 2016 at 12:16:10PM -0300, Arnaldo Carvalho de Melo escreveu:
> Perhaps, to make all more familiar we could even define equivalents to
> stdio.h functions like puts, printf, fputs, etc, that would send to this
> bpf-output based "stdout" "channel", then the above would end up being:
> 
>  func(void *ctx, int type)
>  {
>         char err_str[] = "BAD %d\n";
>         int err;
> 
>         err = puts("Raise a BPF event!");
>         if (err)
>                 trace_printk(err_str, sizeof(err_str), err);
>         return 1;
>  }
> 
> This trace_printk() in turn could become error() (glibc's error.h header), i.e.
> the error mechanism would use the equivalent to userland's "syslog", i.e.
> trace_printk :-)
> 
> In general trying to make BPF C scriptlets fed via perf to be as compact as
> possible, hiding all these details while allowing them to be used, if desired.

One extra possibility would be that it would look so much like a user
space C program that we could test it without loading it to the kernel,
with just building it with a different header and feeding it data as it
would get inside the kernel :-)

- Arnaldo