Re: [PATCH 1/6] perf top: teach it to autolocate vmlinux

Arnaldo Carvalho de Melo
2010-01-13T13:40:09Z

Em Fri, Jan 08, 2010 at 03:23:04PM +0300, Kirill Smelkov escreveu:
> By relying on logic in dso__load_kernel_sym(), we can automatically load
> vmlinux.
>
> The only thing which needs to be adjusted, is how --sym-annotate option
> is handled - now we can't rely on vmlinux been loaded until full
> successful pass of dso__load_vmlinux(), but that's not the case if we'll
> do sym_filter_entry setup in symbol_filter().
>
> So move this step right after event__process_sample() where we know the
> whole dso__load_kernel_sym() pass is done.
>
> By the way, though conceptually similar `perf top` still can't annotate
> userspace - see next patches with fixes.
>
> Signed-off-by: Kirill Smelkov <kirr@landau.phys.spbu.ru>
> Cc: Mike Galbraith <efault@gmx.de>
> ---

<SNIP>

> @@ -951,6 +953,13 @@ static void event__process_sample(const event_t *self,
> al.sym == NULL || al.filtered)
> return;
>
> + /* let's see, whether we need to install initial sym_filter_entry */
> + if (sym_filter_entry_sched) {
> + sym_filter_entry = sym_filter_entry_sched;
> + sym_filter_entry_sched = NULL;
> + parse_source(sym_filter_entry);
> + }
> +

You're assuming that the first sample is for the kernel, right? It may
be not and then the vmlinux won't be loaded at this point.

I think that the right way is to force it to be loaded by calling:

map__load(session->vmlinux_maps[MAP__FUNCTION], session, filter);

after perf_session__create_kernel_maps and before parse_source(), ok?

You can even create a helper:

int perf_session__load_vmlinux(struct perf_session *self,
symbol_filter_t filter)
{
return map__load(session->vmlinux_maps[MAP__FUNCTION],
session, filter);
}

As this probably will be of interest for tools such as 'perf
probe', etc.

- Arnaldo