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SubjectRe: [PATCH v4 perf,bpf 14/15] perf: introduce side band thread
On Mon, Mar 04, 2019 at 09:40:07PM +0000, Song Liu wrote:
>
>
> > On Feb 27, 2019, at 5:21 AM, Jiri Olsa <jolsa@redhat.com> 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:
> >
> > struct perf_evlist {
> > ...
> > struct {
> > pthread_t th;
> > int state;
> > } thread;
> > };
> >
> > typedef int (perf_evlist__thread_cb_t)(perf_evlist, union perf_event *event,....)
> >
> > perf_evlist__start_thread(perf_evlist, perf_evlist__thread_cb_t cb);
> > perf_evlist__stop_thread(perf_evlist);
> >
> >
> > jirka
>
> More questions on this proposal:
>
> IIUC, this approach creates one perf_evlist and one thread for each side band
> event (only bpf for now, more afterwards). Each of these perf_evlists will
> create its own ring buffer.
>
> On the other hand, current patch allows different events to share the thread,
> the perf_evlist, and the ring buffer.

you can have those events in single evlist no?

>
> If my understanding is correct, current patch would be more efficient down the
> road? Did I miss some downsides of current patch?

I'd just like something configurable and with single handle
not scattered around the code, so it's easy to add new callback
jirka

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