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

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Date:   Tue, 6 Dec 2016 16:19:34 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        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>
Subject: Re: [PATCH v3 10/30] perf clang: Add builtin clang support ant test
 case

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@...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

It was ON, rebuilding it with

$ cmake -DCMAKE_BUILD_TYPE=Release /home/acme/git/llvm
$ make -j4

Will take a (another) while :-)

- 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.