Re: [PATCH 2/2] perf record: Add --dry-run option to check cmdline options

[Wangnan (F)]

On 2016/6/21 0:22, Alexei Starovoitov wrote:
> On Mon, Jun 20, 2016 at 11:38:18AM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Mon, Jun 20, 2016 at 11:29:13AM +0800, Wangnan (F) escreveu:
> > > On 2016/6/17 0:48, Arnaldo Carvalho de Melo wrote:
> > > > Em Thu, Jun 16, 2016 at 08:02:41AM +0000, Wang Nan escreveu:
> > > > > With '--dry-run', 'perf record' doesn't do reall recording. Combine with
> > > > > llvm.dump-obj option, --dry-run can be used to help compile BPF objects for
> > > > > embedded platform.
> > > > So these are nice and have value, but can we have a subcommand to do all
> > > > this with an expressive name, Something like:
> > > >    perf bpfcc foo.c -o foo
> > > > or shorter:
> > > >    perf bcc foo.c -o foo
> > > > Just like one would use gcc or some other compiler to generate something
> > > > for later use?
> > > I'll try it today. I thought a subcommand require a bigger feature,
> > > and wrapping clang is not big enough.
> > Not really, we may have as many as we like, given that they provide
> > something useful, like I think is the case here.
> >
> > Having to edit ~/.perfconfig, create a new section, a variable in it
> > with a boolean value (at first, just reading the changeset comment, I
> > thought I had to provide a directory where to store the objects
> > "dumped"), to then use a tool to record a .c event, but not recording
> > (use dry-run, which is useful to test the command line, etc), to then
> > get, on the current directory, the end result looked to me a convoluted
> > way to ask perf to compile the given .c file into a .o for later use.
> >
> > Doing:
> >
> > 	perf bcc -c foo.c
> >
> > Looks so much simpler and similar to an existing compile source code
> > into object file workflow (gcc's, any C compiler) that I think it would
> > fit in the workflow being discussed really nicely.
> I'm hopeful that eventually we'll be able merge iovisor/bcc project
> with perf, so would be good to reserve 'perf bcc' command for that
> future use. Also picking a different name for compiling would be less
> confusing to users who already familiar with bcc. Instead we can use:
> perf bpfcc foo.c -o foo.o
> perf cc foo.c
> perf compile foo.c

I think finally we should make perf independent with LLVM runtime.
I suggest 'perf bpf' subcommand to deal with all BPF related things,
include compiling, configuration and potential cache.

Thank you.