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Date: Thu, 12 Nov 2020 16:07:50 +0530
From: Linu Cherian <linuc.decode@...il.com>
To: Suzuki K Poulose <suzuki.poulose@....com>
Cc: Anshuman Khandual <anshuman.khandual@....com>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
Coresight ML <coresight@...ts.linaro.org>,
linux-kernel@...r.kernel.org,
Mathieu Poirier <mathieu.poirier@...aro.org>,
Mike Leach <mike.leach@...aro.org>,
Linu Cherian <lcherian@...vell.com>
Subject: Re: [RFC 02/11] coresight: etm-perf: Allow an event to use different sinks
Hi Suzuki,
On Thu, Nov 12, 2020 at 2:51 PM Suzuki K Poulose <suzuki.poulose@....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@....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@....com>
> > Signed-off-by: Anshuman Khandual <anshuman.khandual@....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@...vell.com>
Thanks.
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