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Message-Id: <20211102180739.18049-4-german.gomez@arm.com>
Date: Tue, 2 Nov 2021 18:07:39 +0000
From: German Gomez <german.gomez@....com>
To: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
acme@...nel.org
Cc: German Gomez <german.gomez@....com>,
John Garry <john.garry@...wei.com>,
Will Deacon <will@...nel.org>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
Leo Yan <leo.yan@...aro.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 3/3] perf arm-spe: Support hardware-based PID tracing
If Arm SPE traces contain CONTEXT packets with PID info, use these
values for tracking pid of samples. Otherwise fall back to using context
switch events and display a message warning the user of possible timing
inaccuracies [1].
[1] https://lore.kernel.org/lkml/f877cfa6-9b25-6445-3806-ca44a4042eaf@arm.com/
Signed-off-by: German Gomez <german.gomez@....com>
---
tools/perf/util/arm-spe.c | 123 ++++++++++++++++++++++++++++----------
1 file changed, 92 insertions(+), 31 deletions(-)
diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
index 230bc7ab2..00a409469 100644
--- a/tools/perf/util/arm-spe.c
+++ b/tools/perf/util/arm-spe.c
@@ -71,6 +71,7 @@ struct arm_spe {
u64 kernel_start;
unsigned long num_events;
+ u8 use_ctx_pkt_for_pid;
};
struct arm_spe_queue {
@@ -226,6 +227,44 @@ static inline u8 arm_spe_cpumode(struct arm_spe *spe, u64 ip)
PERF_RECORD_MISC_USER;
}
+static void arm_spe_set_pid_tid_cpu(struct arm_spe *spe,
+ struct auxtrace_queue *queue)
+{
+ struct arm_spe_queue *speq = queue->priv;
+ pid_t tid;
+
+ tid = machine__get_current_tid(spe->machine, speq->cpu);
+ if (tid != -1) {
+ speq->tid = tid;
+ thread__zput(speq->thread);
+ } else
+ speq->tid = queue->tid;
+
+ if ((!speq->thread) && (speq->tid != -1)) {
+ speq->thread = machine__find_thread(spe->machine, -1,
+ speq->tid);
+ }
+
+ if (speq->thread) {
+ speq->pid = speq->thread->pid_;
+ if (queue->cpu == -1)
+ speq->cpu = speq->thread->cpu;
+ }
+}
+
+static int arm_spe_set_tid(struct arm_spe_queue *speq, pid_t tid)
+{
+ struct arm_spe *spe = speq->spe;
+ int err = machine__set_current_tid(spe->machine, speq->cpu, tid, tid);
+
+ if (err)
+ return err;
+
+ arm_spe_set_pid_tid_cpu(spe, &spe->queues.queue_array[speq->queue_nr]);
+
+ return 0;
+}
+
static void arm_spe_prep_sample(struct arm_spe *spe,
struct arm_spe_queue *speq,
union perf_event *event,
@@ -460,6 +499,13 @@ static int arm_spe_run_decoder(struct arm_spe_queue *speq, u64 *timestamp)
* can correlate samples between Arm SPE trace data and other
* perf events with correct time ordering.
*/
+
+ if (spe->use_ctx_pkt_for_pid) {
+ ret = arm_spe_set_tid(speq, speq->decoder->record.context_id);
+ if (ret)
+ return ret;
+ }
+
ret = arm_spe_sample(speq);
if (ret)
return ret;
@@ -586,31 +632,6 @@ static bool arm_spe__is_timeless_decoding(struct arm_spe *spe)
return timeless_decoding;
}
-static void arm_spe_set_pid_tid_cpu(struct arm_spe *spe,
- struct auxtrace_queue *queue)
-{
- struct arm_spe_queue *speq = queue->priv;
- pid_t tid;
-
- tid = machine__get_current_tid(spe->machine, speq->cpu);
- if (tid != -1) {
- speq->tid = tid;
- thread__zput(speq->thread);
- } else
- speq->tid = queue->tid;
-
- if ((!speq->thread) && (speq->tid != -1)) {
- speq->thread = machine__find_thread(spe->machine, -1,
- speq->tid);
- }
-
- if (speq->thread) {
- speq->pid = speq->thread->pid_;
- if (queue->cpu == -1)
- speq->cpu = speq->thread->cpu;
- }
-}
-
static int arm_spe_process_queues(struct arm_spe *spe, u64 timestamp)
{
unsigned int queue_nr;
@@ -641,7 +662,13 @@ static int arm_spe_process_queues(struct arm_spe *spe, u64 timestamp)
ts = timestamp;
}
- arm_spe_set_pid_tid_cpu(spe, queue);
+ /*
+ * Here we only consider PID tracking based on switch events.
+ * For tracking based on CONTEXT packets, the pid is assigned in the function
+ * arm_spe_run_decoder() in order to support timeless decoding.
+ */
+ if (!spe->use_ctx_pkt_for_pid)
+ arm_spe_set_pid_tid_cpu(spe, queue);
ret = arm_spe_run_decoder(speq, &ts);
if (ret < 0) {
@@ -740,8 +767,9 @@ static int arm_spe_process_event(struct perf_session *session,
if (err)
return err;
- if (event->header.type == PERF_RECORD_SWITCH_CPU_WIDE ||
- event->header.type == PERF_RECORD_SWITCH)
+ if (!spe->use_ctx_pkt_for_pid &&
+ (event->header.type == PERF_RECORD_SWITCH_CPU_WIDE ||
+ event->header.type == PERF_RECORD_SWITCH))
err = arm_spe_context_switch(spe, event, sample);
}
@@ -805,10 +833,16 @@ static int arm_spe_flush(struct perf_session *session __maybe_unused,
return ret;
if (spe->timeless_decoding)
- return arm_spe_process_timeless_queues(spe, -1,
+ ret = arm_spe_process_timeless_queues(spe, -1,
MAX_TIMESTAMP - 1);
+ else
+ ret = arm_spe_process_queues(spe, MAX_TIMESTAMP);
- return arm_spe_process_queues(spe, MAX_TIMESTAMP);
+ if (!spe->use_ctx_pkt_for_pid)
+ ui__warning("Arm SPE CONTEXT packets not found in the traces.\n\n"
+ "Matching of TIDs to SPE events could be inaccurate.\n\n");
+
+ return ret;
}
static void arm_spe_free_queue(void *priv)
@@ -1056,6 +1090,22 @@ arm_spe_synth_events(struct arm_spe *spe, struct perf_session *session)
return 0;
}
+static bool arm_spe_is_ctx_pkt_enabled(struct arm_spe *spe)
+{
+ struct auxtrace_queues *queues = &spe->queues;
+ unsigned int i;
+
+ for (i = 0; i < queues->nr_queues; i++) {
+ struct auxtrace_queue *queue = &spe->queues.queue_array[i];
+ struct arm_spe_queue *speq = queue->priv;
+
+ if (speq)
+ return speq->decoder->record.context_id != (u64) -1;
+ }
+
+ return false;
+}
+
int arm_spe_process_auxtrace_info(union perf_event *event,
struct perf_session *session)
{
@@ -1131,9 +1181,20 @@ int arm_spe_process_auxtrace_info(union perf_event *event,
if (err)
goto err_free_queues;
- if (spe->queues.populated)
+ if (spe->queues.populated) {
spe->data_queued = true;
+ /*
+ * Ensure the first record of every queue can be read in the function
+ * arm_spe_is_ctx_pkt_enabled()
+ */
+ err = arm_spe__update_queues(spe);
+ if (err)
+ goto err_free_queues;
+
+ spe->use_ctx_pkt_for_pid = arm_spe_is_ctx_pkt_enabled(spe);
+ }
+
return 0;
err_free_queues:
--
2.25.1
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