Re: [PATCHv3 00/12] perf tools: Display eBPF code in intel_pt trace

Jiri Olsa
2019-05-30T13:28:11Z

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/@20070000.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