linux-kernel - Re: [PATCH v3 10/30] perf clang: Add builtin clang support ant test case

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Date:   Mon, 5 Dec 2016 08:51:01 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:     Wang Nan <wangnan0@...wei.com>, ast@...com, lizefan@...wei.com,
        hekuang@...wei.com, Ingo Molnar <mingo@...nel.org>,
        linux-kernel@...r.kernel.org, pi3orama@....com, joe@....org,
        Jiri Olsa <jolsa@...nel.org>, acme@...nel.org
Subject: Re: [PATCH v3 10/30] perf clang: Add builtin clang support ant test
 case

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@...et ~]# size /tmp/perf
>    text	   data	    bss	    dec	    hex	filename
> 75333688	1421584	23962176	100717448	600d388 /tmp/perf
> [root@...et ~]#
> 
> I've built it with this:
> 
>   make LIBCLANGLLVM=1 O=/tmp/build/perf -C tools/perf install-bin
> 
> the resulting binary:
> 
> [acme@...et linux]$ 
> [acme@...et linux]$ ls -la ~/bin/perf
> -rwxr-xr-x. 2 acme acme 131689136 Dec  2 12:31 /home/acme/bin/perf
> [acme@...et linux]$ ls -lah ~/bin/perf
> -rwxr-xr-x. 2 acme acme 126M Dec  2 12:31 /home/acme/bin/perf
> [acme@...et linux]$
> 
> Huge, after stripping it:
> 
> [acme@...et linux]$ ls -la /tmp/perf
> -rwxr-xr-x. 1 root root 76759056 Dec  2 12:33 /tmp/perf
> [acme@...et linux]$ ls -lah /tmp/perf
> -rwxr-xr-x. 1 root root 74M Dec  2 12:33 /tmp/perf
> [acme@...et 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

> 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.