Re: [PATCH v4 perf,bpf 14/15] perf: introduce side band thread

From: Jiri Olsa
Date: Mon Mar 04 2019 - 08:53:34 EST


On Wed, Feb 27, 2019 at 05:52:52PM +0000, Song Liu wrote:
>
>
> > On Feb 27, 2019, at 5:21 AM, Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> >
> > On Mon, Feb 25, 2019 at 04:20:18PM -0800, Song Liu wrote:
> >
> > SNIP
> >
> >> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> >> index 8c902276d4b4..61b87c8111e6 100644
> >> --- a/tools/perf/util/evlist.c
> >> +++ b/tools/perf/util/evlist.c
> >> @@ -19,6 +19,7 @@
> >> #include "debug.h"
> >> #include "units.h"
> >> #include "asm/bug.h"
> >> +#include "bpf-event.h"
> >> #include <signal.h>
> >> #include <unistd.h>
> >>
> >> @@ -1841,3 +1842,102 @@ struct perf_evsel *perf_evlist__reset_weak_group(struct perf_evlist *evsel_list,
> >> }
> >> return leader;
> >> }
> >> +
> >> +static struct perf_evlist *sb_evlist;
> >> +pthread_t poll_thread;
> >
> > so some of the things are static and some like poll_args
> > you alloced on the stack.. I dont like this interface,
> > could we come up with something generic? perhaps
> > encapsulated in perf_evlist, like:
>
> I picked global sb_evlist and poll_thread because there
> should be only one sb_evlist and one thread polling it.
> There might be multiple evsel on the sb_evlist.
>
> I am not sure I understand your suggestion..
>
> > struct perf_evlist {
> > ...
> > struct {
> > pthread_t th;
> > int state;
> > } thread;
>
> This will not be used by the main perf_evlist, right?

no, just by the thread interface

>
> > };
> >
> > typedef int (perf_evlist__thread_cb_t)(perf_evlist, union perf_event *event,....)
>
> How do we use this callback? We need a way to specify which
> events to poll (mmap, bpf_event, ksymbol, etc). How do we do
> that with the callback function?

you provide your own callback

jirka