Re: [GIT PULL 0/6] perf/core improvements and fixes

[Alexei Starovoitov]

On 6/4/15 2:48 PM, Masami Hiramatsu wrote:
> On 2015/06/05 1:22, Alexei Starovoitov wrote:
> > On 6/4/15 7:04 AM, Ingo Molnar wrote:
> > > > >   # perf record -e bpf_source.c cmdline
> > > > >
> > > > >   to create a eBPF filter from source,
> > > > >
> > > > > Use
> > > > >
> > > > > # perf record -e bpf_object.o cmdline
> > > > >
> > > > > to create a eBPF filter from object intermedia.
> > > > >
> > > > > Use
> > > > >
> > > > > # perf bpf compile bpf_source.c --kbuild=kernel-build-dir -o bpf_object.o
> > > > >
> > > > > to create the .o
> > > > >
> > > > > I think this should be enough. Currently only the second case has been implemented.
> > > So if users cannot actually generate .o files then it's premature to merge this in
> > > such an incomplete form!
> > >
> > > It should be possible to use a feature that we are merging.
> >
> > of course it's usable :) There is some confusion here.
> > To compile .c into .o one can easily use
> > clang -O2 -emit-llvm -c file.c -o - | llc -march=bpf -o file.o
> > any version of clang is ok,
> > llc needs to be fresh with bpf backend.
> >
> > For a lot of cases kernel headers are not needed, so above
> > will work fine.
> > For our TC examples we recommend to use 'bcc' alias:
> > bcc() {
> >     clang -O2 -emit-llvm -c $1 -o - | llc -march=bpf -filetype=obj -o
> > "`basename $1 .c`.o"
> > }
> > then compiling as easy as 'bcc file.c'
> >
> > What Wang mentioned that we're working on is fully integrated 'bcc'.
> > It will use clang/llvm as libraries, so no intermediate steps will
> > be needed, but some folks will always have concerns about
> > ultra-embedded environments where even 20Mb of libllvm.so is too much.
> >
> > So I think we need to support both 'perf record -e file.[co]'
>
> I think we'd better make 'perf record -e file.c' default and '-e file.o'
> should be an option.

what do you mean 'default' ? It's a command line :)
.c is easier to use of course, no question.

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