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perf/x86/intel/pt: Add sampling support

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Add AUX sampling support to the PT PMU: implement an NMI-safe callback
that takes a snapshot of the buffer without touching the event states.
This is done for PT events that don't use PMIs, that is, snapshot mode
(RO mapping of the AUX area).

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: adrian.hunter@intel.com
Cc: mathieu.poirier@linaro.org
Link: https://lkml.kernel.org/r/20191025140835.53665-4-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Alexander Shishkin 2019-10-25 17:08:35 +03:00 committed by Ingo Molnar
parent 8e105a1fc2
commit 25e8920b30
1 changed files with 54 additions and 0 deletions
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54
arch/x86/events/intel/pt.c
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@ -1208,6 +1208,13 @@ pt_buffer_setup_aux(struct perf_event *event, void **pages,
if (!nr_pages)
return NULL;
/*
* Only support AUX sampling in snapshot mode, where we don't
* generate NMIs.
*/
if (event->attr.aux_sample_size && !snapshot)
return NULL;
if (cpu == -1)
cpu = raw_smp_processor_id();
node = cpu_to_node(cpu);
@ -1506,6 +1513,52 @@ static void pt_event_stop(struct perf_event *event, int mode)
}
}
static long pt_event_snapshot_aux(struct perf_event *event,
struct perf_output_handle *handle,
unsigned long size)
{
struct pt *pt = this_cpu_ptr(&pt_ctx);
struct pt_buffer *buf = perf_get_aux(&pt->handle);
unsigned long from = 0, to;
long ret;
if (WARN_ON_ONCE(!buf))
return 0;
/*
* Sampling is only allowed on snapshot events;
* see pt_buffer_setup_aux().
*/
if (WARN_ON_ONCE(!buf->snapshot))
return 0;
/*
* Here, handle_nmi tells us if the tracing is on
*/
if (READ_ONCE(pt->handle_nmi))
pt_config_stop(event);
pt_read_offset(buf);
pt_update_head(pt);
to = local_read(&buf->data_size);
if (to < size)
from = buf->nr_pages << PAGE_SHIFT;
from += to - size;
ret = perf_output_copy_aux(&pt->handle, handle, from, to);
/*
* If the tracing was on when we turned up, restart it.
* Compiler barrier not needed as we couldn't have been
* preempted by anything that touches pt->handle_nmi.
*/
if (pt->handle_nmi)
pt_config_start(event);
return ret;
}
static void pt_event_del(struct perf_event *event, int mode)
{
pt_event_stop(event, PERF_EF_UPDATE);
@ -1625,6 +1678,7 @@ static __init int pt_init(void)
pt_pmu.pmu.del = pt_event_del;
pt_pmu.pmu.start = pt_event_start;
pt_pmu.pmu.stop = pt_event_stop;
pt_pmu.pmu.snapshot_aux = pt_event_snapshot_aux;
pt_pmu.pmu.read = pt_event_read;
pt_pmu.pmu.setup_aux = pt_buffer_setup_aux;
pt_pmu.pmu.free_aux = pt_buffer_free_aux;