Date: Mon, 5 Dec 2016 19:02:48 -0200
From: Arnaldo Carvalho de Melo <acme@redhat.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Wang Nan <wangnan0@huawei.com>, ast@fb.com, lizefan@huawei.com,
        hekuang@huawei.com, Ingo Molnar <mingo@kernel.org>,
        linux-kernel@vger.kernel.org, pi3orama@163.com, joe@ovn.org,
        Jiri Olsa <jolsa@kernel.org>, acme@kernel.org
Subject: Re: [PATCH v3 10/30] perf clang: Add builtin clang support ant test
 case
Message-ID: <20161205210248.GA2247@redhat.com>
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 <20161202154440.GB5931@redhat.com>
 <20161205165055.GB79989@ast-mbp.thefacebook.com>
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Em Mon, Dec 05, 2016 at 08:51:01AM -0800, Alexei Starovoitov escreveu:
> On Fri, Dec 02, 2016 at 01:44:40PM -0200, Arnaldo Carvalho de Melo wrote:
> > Em Sat, Nov 26, 2016 at 07:03:34AM +0000, Wang Nan escreveu:
> > > Add basic clang support in clang.cpp and test__clang() testcase. The
> > > first testcase checks if builtin clang is able to generate LLVM IR.
> > > 
> > > tests/clang.c is a proxy. Real testcase resides in
> > > utils/c++/clang-test.cpp in c++ and exports C interface to perf test
> > > subsystem.
> > > 
> > > Test result:
> > > 
> > >    $ perf test -v clang
> > >    51: Test builtin clang support                               :
> > >    51.1: Test builtin clang compile C source to IR              :
> > >    --- start ---
> > >    test child forked, pid 13215
> > >    test child finished with 0
> > >    ---- end ----
> > >    Test builtin clang support subtest 0: Ok
> > 
> > While testing this I noticed that the perf binary got huge, can't this
> > be done in some other way, i.e. using dynamic library?
> > 
> > [root@jouet ~]# size /tmp/perf
> >    text	   data	    bss	    dec	    hex	filename
> > 75333688	1421584	23962176	100717448	600d388 /tmp/perf
> > [root@jouet ~]#
> > 
> > I've built it with this:
> > 
> >   make LIBCLANGLLVM=1 O=/tmp/build/perf -C tools/perf install-bin
> > 
> > the resulting binary:
> > 
> > [acme@jouet linux]$ 
> > [acme@jouet linux]$ ls -la ~/bin/perf
> > -rwxr-xr-x. 2 acme acme 131689136 Dec  2 12:31 /home/acme/bin/perf
> > [acme@jouet linux]$ ls -lah ~/bin/perf
> > -rwxr-xr-x. 2 acme acme 126M Dec  2 12:31 /home/acme/bin/perf
> > [acme@jouet linux]$
> > 
> > Huge, after stripping it:
> > 
> > [acme@jouet linux]$ ls -la /tmp/perf
> > -rwxr-xr-x. 1 root root 76759056 Dec  2 12:33 /tmp/perf
> > [acme@jouet linux]$ ls -lah /tmp/perf
> > -rwxr-xr-x. 1 root root 74M Dec  2 12:33 /tmp/perf
> > [acme@jouet linux]$
> > 
> > Still huge :-\
> 
> yeah. it's kinda high. I'm guessing rpm llvm libs are in debug mode.
> Try llvm-config --build-mode --assertion-mode
> it should be Release OFF

Probably this was with 3.9 and built from git, quite a while ago, now I
removed it from /usr/local/ and installed what is in f25, but I fear it
will be insufficient, does 3.8 cuts it for what we're testing? Humm, it
looks like it will:

[root@jouet ~]# llc --version
LLVM (http://llvm.org/):
  LLVM version 3.8.0
  Optimized build.
  Built Mar 10 2016 (01:41:45).
  Default target: x86_64-unknown-linux-gnu
  Host CPU: broadwell

  Registered Targets:
    aarch64    - AArch64 (little endian)
    aarch64_be - AArch64 (big endian)
    amdgcn     - AMD GCN GPUs
    arm        - ARM
    arm64      - ARM64 (little endian)
    armeb      - ARM (big endian)
    bpf        - BPF (host endian)
    bpfeb      - BPF (big endian)
    bpfel      - BPF (little endian)
    cpp        - C++ backend
    nvptx      - NVIDIA PTX 32-bit
    nvptx64    - NVIDIA PTX 64-bit
    ppc32      - PowerPC 32
    ppc64      - PowerPC 64
    ppc64le    - PowerPC 64 LE
    r600       - AMD GPUs HD2XXX-HD6XXX
    systemz    - SystemZ
    thumb      - Thumb
    thumbeb    - Thumb (big endian)
    x86        - 32-bit X86: Pentium-Pro and above
    x86-64     - 64-bit X86: EM64T and AMD64
[root@jouet ~]# 

But I'm now running the container based tests to send a pull req, will
check later, after that.

- Arnaldo
 
> > But being a n00b on llvm/clang libraries, etc, my question goes back to:
> > can we have this using a libllvm.so or libclang.so dynamic libraries?
> 
> that can also work. The reason we build iovisor/bcc into single binary
> is to ease operational headache.