linux-kernel - Re: perf eBPF patch ordering. was: Re: perf test LLVM was: Re: [GIT PULL 00/39] perf tools: filtering events using eBPF programs

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Date:	Mon, 3 Aug 2015 13:11:16 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	pi3orama <pi3orama@....com>
Cc:	"Wangnan (F)" <wangnan0@...wei.com>, He Kuang <hekuang@...wei.com>,
	Li Zefan <lizefan@...wei.com>,
	"ast@...mgrid.com" <ast@...mgrid.com>,
	"xiakaixu@...wei.com" <xiakaixu@...wei.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
	David Ahern <dsahern@...il.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: perf eBPF patch ordering.  was: Re: perf test LLVM was: Re: [GIT
 PULL 00/39] perf tools: filtering events using eBPF programs

Em Mon, Aug 03, 2015 at 11:53:05PM +0800, pi3orama escreveu:
> 
> 
> 发自我的 iPhone
> 
> > 在 2015年8月3日，下午11:19，Arnaldo Carvalho de Melo <acme@...nel.org> 写道：
> > 
> > Em Mon, Aug 03, 2015 at 12:07:28PM -0300, Arnaldo Carvalho de Melo escreveu:
> >> Em Mon, Aug 03, 2015 at 10:37:59AM +0800, Wangnan (F) escreveu:
> >>> On 2015/8/1 4:31, Arnaldo Carvalho de Melo wrote:
> >>>> Somehow it is not calling what the changeset says it would call when passing
> >>>> "-e foo.o", investigating...
> >> 
> >>> Have you tried
> >> 
> >>> /root/bin/perf record -e ./foo.o sleep 1
> >> 
> >>> The key is './'.
> >> 
> >> Nope, trying it now I get:
> >> 
> >>  [root@...icio ~]# perf record -e ./foo.o sleep 1
> >>  libbpf: failed to open ./foo.o: No such file or directory
> >>  bpf: failed to load ./foo.o
> > 
> > And with a .c suffix:
> > 
> >  [root@...icio ~]# perf record -e ./foo.c sleep 1
> >  clang-3.8: error: no such file or directory: '/root/./foo.c'
> >  clang-3.8: error: no input files
> 
> What's the content of your foo.c? Could you please have a look?

I said:

> > Now to find a hello.c BPF scriptlet...

Because, as clang says: "error: no such file or directory: '/root/./foo.c'"

It doesn't exists :-)
 
> I considered moving .o enabler down so when you see that patch the filter will be
>  workable. However , like the llvm support, doing so will enable a bulk of code by
> one patch, that's not good. Moving .c enabler down is easy.

Right, probably leaving the .c enabler to be the last one, together with
a "hello_bpf.c" that we can use in testing it is best.
 
> Now I'm working on a BPF testcase. Tomorrow you will see a new test:
 
> # perf test BPF
 
> It enforces test__llvm, and forks a 'perf record' to do the filtering, then checks the
> result using perf report -D. The patch of the new test is a mark which indicates the
> basic function of BPF filter is done. What do you think about this idea?

Excellent idea, you could even save the intermediary .o file and use it
in another test :-)

Sometimes we can't straight away test some infrastructure because the
patch at hand is just glue, that will later be used by a tool, 'perf
record', say, in those cases we can test this glue by using it in a
'perf test' entry.

Thanks!

- Arnaldo
 
> Thank you.
> 
> >  ERROR:    unable to compile ./foo.c
> >  Hint:    Check error message shown above.
> >         LLVM 3.7 or newer is required. Which can be found from http://llvm.org
> >         You may want to try git trunk:
> >             git clone http://llvm.org/git/llvm.git
> >                  and
> >             git clone http://llvm.org/git/clang.git
> > 
> >         Or fetch the latest clang/llvm 3.7 from pre-built llvm packages for
> >         debian/ubuntu:
> >             http://llvm.org/apt
> > 
> >         If you are using old version of clang, change 'clang-bpf-cmd-template'
> >         option in [llvm] section of ~/.perfconfig to:
> > 
> >           "$CLANG_EXEC $CLANG_OPTIONS $KERNEL_INC_OPTIONS \
> >              -working-directory $WORKING_DIR -c $CLANG_SOURCE \
> >              -emit-llvm -o - | /path/to/llc -march=bpf -filetype=obj -o -"
> >         (Replace /path/to/llc with path to your llc)
> > 
> >  Hint:    You can also pre-compile it into .o
> >  invalid or unsupported event: './foo.c'
> >  Run 'perf list' for a list of valid events
> > 
> >   usage: perf record [<options>] [<command>]
> >      or: perf record [<options>] -- <command> [<options>]
> > 
> >      -e, --event <event>   event selector. use 'perf list' to list available events
> >  [root@...icio ~]#
> > 
> > Now to find a hello.c BPF scriptlet...
> > 
> > - Arnaldo
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