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

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Message-ID: <20190530132749.GB3669@krava>
Date:   Thu, 30 May 2019 15:27:49 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Leo Yan <leo.yan@...aro.org>
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

On Thu, May 30, 2019 at 08:57:09PM +0800, Leo Yan wrote:
> 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?

no it's just test_verifier exits right away with ebpf code,
and perf does not have a chance to get the ebpf prog info

your example above should be fine.. I'll try

> 
> 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?

yes, the standard sample/annotate support was already in perf

jirka