[PATCH 4/4] eal: add PMU support to tracing library

[Tomasz Duszynski <tduszynski@marvell.com>]

In order to profile app one needs to store significant amount of samples
somewhere for an analysis latern on. Since trace library supports
storing data in a CTF format lets take adventage of that and add a
dedicated PMU tracepoint.

Signed-off-by: Tomasz Duszynski <tduszynski@marvell.com>
---
 app/test/test_trace_perf.c               |  4 ++
 doc/guides/prog_guide/profile_app.rst    |  5 ++
 doc/guides/prog_guide/trace_lib.rst      | 32 ++++++++++++
 lib/eal/common/eal_common_trace_points.c |  3 ++
 lib/eal/common/rte_pmu.c                 | 63 ++++++++++++++++++++++++
 lib/eal/include/rte_eal_trace.h          | 11 +++++
 lib/eal/version.map                      |  1 +
 7 files changed, 119 insertions(+)

diff --git a/app/test/test_trace_perf.c b/app/test/test_trace_perf.c
index 46ae7d8074..4851b6852f 100644
--- a/app/test/test_trace_perf.c
+++ b/app/test/test_trace_perf.c
@@ -114,6 +114,8 @@ worker_fn_##func(void *arg) \
 #define GENERIC_DOUBLE rte_eal_trace_generic_double(3.66666)
 #define GENERIC_STR rte_eal_trace_generic_str("hello world")
 #define VOID_FP app_dpdk_test_fp()
+/* 0 corresponds first event passed via --trace= */
+#define READ_PMU rte_eal_trace_pmu_read(0)
 
 WORKER_DEFINE(GENERIC_VOID)
 WORKER_DEFINE(GENERIC_U64)
@@ -122,6 +124,7 @@ WORKER_DEFINE(GENERIC_FLOAT)
 WORKER_DEFINE(GENERIC_DOUBLE)
 WORKER_DEFINE(GENERIC_STR)
 WORKER_DEFINE(VOID_FP)
+WORKER_DEFINE(READ_PMU)
 
 static void
 run_test(const char *str, lcore_function_t f, struct test_data *data, size_t sz)
@@ -174,6 +177,7 @@ test_trace_perf(void)
 	run_test("double", worker_fn_GENERIC_DOUBLE, data, sz);
 	run_test("string", worker_fn_GENERIC_STR, data, sz);
 	run_test("void_fp", worker_fn_VOID_FP, data, sz);
+	run_test("read_pmu", worker_fn_READ_PMU, data, sz);
 
 	rte_free(data);
 	return TEST_SUCCESS;
diff --git a/doc/guides/prog_guide/profile_app.rst b/doc/guides/prog_guide/profile_app.rst
index 8fc1b20cab..977800ea01 100644
--- a/doc/guides/prog_guide/profile_app.rst
+++ b/doc/guides/prog_guide/profile_app.rst
@@ -16,6 +16,11 @@ that information, perf being an example here. Though in some scenarios, eg. when
 isolated (nohz_full) and run dedicated tasks, using perf is less than ideal. In such cases one can
 read specific events directly from application via ``rte_pmu_read()``.
 
+Alternatively tracing library can be used which offers dedicated tracepoint
+``rte_eal_trace_pmu_event()``.
+
+Refer to :doc:`../prog_guide/trace_lib` for more details.
+
 Profiling on x86
 ----------------
 
diff --git a/doc/guides/prog_guide/trace_lib.rst b/doc/guides/prog_guide/trace_lib.rst
index 9a8f38073d..9a845fd86f 100644
--- a/doc/guides/prog_guide/trace_lib.rst
+++ b/doc/guides/prog_guide/trace_lib.rst
@@ -46,6 +46,7 @@ DPDK tracing library features
   trace format and is compatible with ``LTTng``.
   For detailed information, refer to
   `Common Trace Format <https://diamon.org/ctf/>`_.
+- Support reading PMU events on ARM64 and x86 (Intel)
 
 How to add a tracepoint?
 ------------------------
@@ -137,6 +138,37 @@ the user must use ``RTE_TRACE_POINT_FP`` instead of ``RTE_TRACE_POINT``.
 ``RTE_TRACE_POINT_FP`` is compiled out by default and it can be enabled using
 the ``enable_trace_fp`` option for meson build.
 
+PMU tracepoint
+--------------
+
+Performance measurement unit (PMU) event values can be read from hardware
+registers using predefined ``rte_pmu_read`` tracepoint.
+
+Tracing is enabled via ``--trace`` EAL option by passing both expression
+matching PMU tracepoint name i.e ``lib.eal.pmu.read`` and expression
+``e=ev1[,ev2,...]`` matching particular events::
+
+    --trace='*pmu.read\|e=cpu_cycles,l1d_cache'
+
+Event names are available under ``/sys/bus/event_source/devices/PMU/events``
+directory, where ``PMU`` is a placeholder for either a ``cpu`` or a directory
+containing ``cpus``.
+
+In contrary to other tracepoints this does not need any extra variables
+added to source files. Instead, caller passes index which follows the order of
+events specified via ``--trace`` parameter. In the following example index ``0``
+corresponds to ``cpu_cyclces`` while index ``1`` corresponds to ``l1d_cache``.
+
+.. code-block:: c
+
+ ...
+ rte_eal_trace_pmu_read(0);
+ rte_eal_trace_pmu_read(1);
+ ...
+
+PMU tracing support must be explicitly enabled using the ``enable_trace_fp``
+option for meson build.
+
 Event record mode
 -----------------
 
diff --git a/lib/eal/common/eal_common_trace_points.c b/lib/eal/common/eal_common_trace_points.c
index 0b0b254615..de918ca618 100644
--- a/lib/eal/common/eal_common_trace_points.c
+++ b/lib/eal/common/eal_common_trace_points.c
@@ -75,3 +75,6 @@ RTE_TRACE_POINT_REGISTER(rte_eal_trace_intr_enable,
 	lib.eal.intr.enable)
 RTE_TRACE_POINT_REGISTER(rte_eal_trace_intr_disable,
 	lib.eal.intr.disable)
+
+RTE_TRACE_POINT_REGISTER(rte_eal_trace_pmu_read,
+	lib.eal.pmu.read)
diff --git a/lib/eal/common/rte_pmu.c b/lib/eal/common/rte_pmu.c
index 7d3bd57d1d..40c454f92a 100644
--- a/lib/eal/common/rte_pmu.c
+++ b/lib/eal/common/rte_pmu.c
@@ -18,6 +18,7 @@
 #include <rte_tailq.h>
 
 #include "pmu_private.h"
+#include "eal_trace.h"
 
 #define EVENT_SOURCE_DEVICES_PATH "/sys/bus/event_source/devices"
 
@@ -402,11 +403,70 @@ rte_pmu_add_event(const char *name)
 	return event->index;
 }
 
+static void
+add_events(const char *pattern)
+{
+	char *token, *copy;
+	int ret;
+
+	copy = strdup(pattern);
+	if (!copy)
+		return;
+
+	token = strtok(copy, ",");
+	while (token) {
+		ret = rte_pmu_add_event(token);
+		if (ret < 0)
+			RTE_LOG(ERR, EAL, "failed to add %s event\n", token);
+
+		token = strtok(NULL, ",");
+	}
+
+	free(copy);
+}
+
+static void
+add_events_by_pattern(const char *pattern)
+{
+	regmatch_t rmatch;
+	char buf[BUFSIZ];
+	unsigned int num;
+	regex_t reg;
+
+	/* events are matched against occurrences of e=ev1[,ev2,..] pattern */
+	if (regcomp(&reg, "e=([_[:alnum:]-],?)+", REG_EXTENDED))
+		return;
+
+	for (;;) {
+		if (regexec(&reg, pattern, 1, &rmatch, 0))
+			break;
+
+		num = rmatch.rm_eo - rmatch.rm_so;
+		if (num > sizeof(buf))
+			num = sizeof(buf);
+
+		/* skip e= pattern prefix */
+		memcpy(buf, pattern + rmatch.rm_so + 2, num - 2);
+		buf[num] = '\0';
+		add_events(buf);
+
+		pattern += rmatch.rm_eo;
+	}
+
+	regfree(&reg);
+}
+
 void
 eal_pmu_init(void)
 {
+	struct trace_arg *arg;
+	struct trace *trace;
 	int ret;
 
+	trace = trace_obj_get();
+	if (!trace)
+		RTE_LOG(WARNING, EAL, "tracing not initialized\n");
+
 	pmu = rte_calloc(NULL, 1, sizeof(*pmu), RTE_CACHE_LINE_SIZE);
 	if (!pmu) {
 		RTE_LOG(ERR, EAL, "failed to alloc PMU\n");
@@ -428,6 +488,9 @@ eal_pmu_init(void)
 		goto out;
 	}
 
+	STAILQ_FOREACH(arg, &trace->args, next)
+		add_events_by_pattern(arg->val);
+
 	return;
 out:
 	free(pmu->name);
diff --git a/lib/eal/include/rte_eal_trace.h b/lib/eal/include/rte_eal_trace.h
index 5ef4398230..2a10f63e97 100644
--- a/lib/eal/include/rte_eal_trace.h
+++ b/lib/eal/include/rte_eal_trace.h
@@ -17,6 +17,7 @@ extern "C" {
 
 #include <rte_alarm.h>
 #include <rte_interrupts.h>
+#include <rte_pmu.h>
 #include <rte_trace_point.h>
 
 #include "eal_interrupts.h"
@@ -279,6 +280,16 @@ RTE_TRACE_POINT(
 	rte_trace_point_emit_string(cpuset);
 )
 
+/* PMU */
+RTE_TRACE_POINT_FP(
+	rte_eal_trace_pmu_read,
+	RTE_TRACE_POINT_ARGS(int index),
+	uint64_t val;
+	rte_trace_point_emit_int(index);
+	val = rte_pmu_read(index);
+	rte_trace_point_emit_u64(val);
+)
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/eal/version.map b/lib/eal/version.map
index e870c87493..d6ec3f3b0e 100644
--- a/lib/eal/version.map
+++ b/lib/eal/version.map
@@ -432,6 +432,7 @@ EXPERIMENTAL {
 	rte_thread_set_priority;
 
 	# added in 22.11
+	__rte_eal_trace_pmu_read; # WINDOWS_NO_EXPORT
 	rte_pmu_add_event; # WINDOWS_NO_EXPORT
 	rte_pmu_read; # WINDOWS_NO_EXPORT
 	rte_thread_attr_get_affinity;
-- 
2.25.1