linux-kernel - Re: [PATCHv3 00/12] perf tools: Display eBPF code in intel

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Date:   Thu, 30 May 2019 20:57:09 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Stanislav Fomichev <sdf@...ichev.me>,
        Song Liu <songliubraving@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCHv3 00/12] perf tools: Display eBPF code in intel_pt trace

Hi Jiri,

On Thu, May 30, 2019 at 02:07:10PM +0200, Jiri Olsa wrote:
> On Thu, May 30, 2019 at 06:54:39PM +0800, Leo Yan wrote:
> > Hi Jiri,
> > 
> > On Wed, May 08, 2019 at 03:19:58PM +0200, Jiri Olsa wrote:
> > > hi,
> > > this patchset adds dso support to read and display
> > > bpf code in intel_pt trace output. I had to change
> > > some of the kernel maps processing code, so hopefully
> > > I did not break too many things ;-)
> > > 
> > > It's now possible to see bpf code flow via:
> > > 
> > >   # perf-with-kcore record pt -e intel_pt//ku -- sleep 1
> > >   # perf-with-kcore script pt --insn-trace --xed
> > 
> > This is very interesting work for me!
> > 
> > I want to verify this feature with Arm CoreSight trace, I have one
> > question so that I have more direction for the tesing:
> > 
> > What's the bpf program you are suing for the testing?  e.g. some
> > testing program under the kernel's folder $kernel/samples/bpf?
> > Or you uses perf command to launch bpf program?
> 
> for this I was using tools/testing/selftests/bpf/test_verifier
> 
> I isolated some tests and ran the perf on top of them, like:
> 
>   # perf-with-kcore record pt -e intel_pt//ku -- ./test_verifier ...

Thanks a lot for sharing the info and quick responsing.

I tried to use the program $kernel/samples/bpf/sampleip to verify this
patch set, but seems eBPF dso is not contained properly; below is my
detailed steps:

    # In the first tty
    # cd $kernel/samples/bpf/
    # ./sampleip -F 200 20  => sample ip with 200Hz for 20s

    # In the second tty
    # perf-with-kcore record arm_test -e cs_etm/@...70000.etr/uk -- sleep 1

If I output DSO info with report command it give below info, which
doesn't contain any info for eBPF DSO?

    # perf-with-kcore report arm_test -F,dso

    # Samples: 6M of event 'branches:ku'
    # Event count (approx.): 6340896
    #
    # Shared Object     
    # ..................
    #
      [kernel.kallsyms] 
      ld-2.28.so        
      libc-2.28.so      
      libpthread-2.28.so
      perf              
      sleep             
      [unknown]         

> I had to add some small sleep before the test_verifier exit,
> so the perf bpf thread could catch up and download the program
> details before test_verifier exited.

This seems to me for a 'real' eBPF program, do we also need extra sleep
so that perf bpf can save dso properly?


BTW, I have another question: to display eBPF code, except this feature
can be used by hardware tracing (e.g. intel_pt), it also can be used
by other PMU events and timer events, right?

Thanks,
Leo Yan