Re: [RFC 02/11] coresight: etm-perf: Allow an event to use different sinks

[Linu Cherian <linuc.decode@gmail.com>]

Hi Suzuki,

On Thu, Nov 12, 2020 at 2:51 PM Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
>
> Hi Linu,
>
> Please could you test this slightly modified version and give us
> a Tested-by tag if you are happy with the results ?
>
> Suzuki
>
>
> On 11/10/20 12:45 PM, Anshuman Khandual wrote:
> > From: Suzuki K Poulose <suzuki.poulose@arm.com>
> >
> > When there are multiple sinks on the system, in the absence
> > of a specified sink, it is quite possible that a default sink
> > for an ETM could be different from that of another ETM. However
> > we do not support having multiple sinks for an event yet. This
> > patch allows the event to use the default sinks on the ETMs
> > where they are scheduled as long as the sinks are of the same
> > type.
> >
> > e.g, if we have 1x1 topology with per-CPU ETRs, the event can
> > use the per-CPU ETR for the session. However, if the sinks
> > are of different type, e.g TMC-ETR on one and a custom sink
> > on another, the event will only trace on the first detected
> > sink.
> >
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> > ---
> >   drivers/hwtracing/coresight/coresight-etm-perf.c | 50 ++++++++++++++++++------
> >   1 file changed, 39 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> > index c2c9b12..ea73cfa 100644
> > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> > @@ -204,14 +204,22 @@ static void etm_free_aux(void *data)
> >       schedule_work(&event_data->work);
> >   }
> >
> > +static bool sinks_match(struct coresight_device *a, struct coresight_device *b)
> > +{
> > +     if (!a || !b)
> > +             return false;
> > +     return (sink_ops(a) == sink_ops(b));
> > +}
> > +
> >   static void *etm_setup_aux(struct perf_event *event, void **pages,
> >                          int nr_pages, bool overwrite)
> >   {
> >       u32 id;
> >       int cpu = event->cpu;
> >       cpumask_t *mask;
> > -     struct coresight_device *sink;
> > +     struct coresight_device *sink = NULL;
> >       struct etm_event_data *event_data = NULL;
> > +     bool sink_forced = false;
> >
> >       event_data = alloc_event_data(cpu);
> >       if (!event_data)
> > @@ -222,6 +230,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
> >       if (event->attr.config2) {
> >               id = (u32)event->attr.config2;
> >               sink = coresight_get_sink_by_id(id);
> > +             sink_forced = true;
> >       }
> >
> >       mask = &event_data->mask;
> > @@ -235,7 +244,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
> >        */
> >       for_each_cpu(cpu, mask) {
> >               struct list_head *path;
> > -             struct coresight_device *csdev;
> > +             struct coresight_device *csdev, *new_sink;
> >
> >               csdev = per_cpu(csdev_src, cpu);
> >               /*
> > @@ -249,21 +258,35 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
> >               }
> >
> >               /*
> > -              * No sink provided - look for a default sink for one of the
> > -              * devices. At present we only support topology where all CPUs
> > -              * use the same sink [N:1], so only need to find one sink. The
> > -              * coresight_build_path later will remove any CPU that does not
> > -              * attach to the sink, or if we have not found a sink.
> > +              * No sink provided - look for a default sink for all the devices.
> > +              * We only support multiple sinks, only if all the default sinks
> > +              * are of the same type, so that the sink buffer can be shared
> > +              * as the event moves around. We don't trace on a CPU if it can't
> > +              *
> >                */
> > -             if (!sink)
> > -                     sink = coresight_find_default_sink(csdev);
> > +             if (!sink_forced) {
> > +                     new_sink = coresight_find_default_sink(csdev);
> > +                     if (!new_sink) {
> > +                             cpumask_clear_cpu(cpu, mask);
> > +                             continue;
> > +                     }
> > +                     /* Skip checks for the first sink */
> > +                     if (!sink) {
> > +                             sink = new_sink;
> > +                     } else if (!sinks_match(new_sink, sink)) {
> > +                             cpumask_clear_cpu(cpu, mask);
> > +                             continue;
> > +                     }
> > +             } else {
> > +                     new_sink = sink;
> > +             }
> >
> >               /*
> >                * Building a path doesn't enable it, it simply builds a
> >                * list of devices from source to sink that can be
> >                * referenced later when the path is actually needed.
> >                */
> > -             path = coresight_build_path(csdev, sink);
> > +             path = coresight_build_path(csdev, new_sink);
> >               if (IS_ERR(path)) {
> >                       cpumask_clear_cpu(cpu, mask);
> >                       continue;
> > @@ -284,7 +307,12 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
> >       if (!sink_ops(sink)->alloc_buffer || !sink_ops(sink)->free_buffer)
> >               goto err;
> >
> > -     /* Allocate the sink buffer for this session */
> > +     /*
> > +      * Allocate the sink buffer for this session. All the sinks
> > +      * where this event can be scheduled are ensured to be of the
> > +      * same type. Thus the same sink configuration is used by the
> > +      * sinks.
> > +      */
> >       event_data->snk_config =
> >                       sink_ops(sink)->alloc_buffer(sink, event, pages,
> >                                                    nr_pages, overwrite);
> >
>

Perf record and report worked fine with this as well, with formatting
related opencsd hacks.

Tested-by : Linu Cherian <lcherian@marvell.com>

Thanks.

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