On Fri, Jun 27, 2025 at 5:41 PM Tomasz Duszynski <tduszyn...@marvell.com> wrote:
>
> In order to profile app, one needs to store significant amount of samples
> somewhere for an analysis later on.
> Since trace library supports storing data in a CTF format,
> lets take advantage of that and add a dedicated PMU tracepoint.
>
> Signed-off-by: Tomasz Duszynski <tduszyn...@marvell.com>
> ---
> MAINTAINERS | 1 +
> app/test/test_trace_perf.c | 10 ++++
> doc/guides/prog_guide/profile_app.rst | 5 ++
> doc/guides/prog_guide/trace_lib.rst | 31 ++++++++++
> doc/guides/rel_notes/release_25_07.rst | 2 +
> lib/eal/common/eal_common_trace.c | 5 +-
> lib/eal/common/eal_common_trace_pmu.c | 38 ++++++++++++
> lib/eal/common/eal_common_trace_points.c | 20 +++++++
> lib/eal/common/eal_trace.h | 4 ++
> lib/eal/common/meson.build | 1 +
> lib/eal/include/rte_eal_trace.h | 16 +++++
> lib/eal/include/rte_trace_point.h | 7 +++
> lib/eal/include/rte_trace_point_register.h | 2 +
> lib/eal/meson.build | 3 +
> lib/meson.build | 2 +-
> lib/pmu/pmu.c | 69 +++++++++++++++++++++-
> lib/pmu/rte_pmu.h | 24 ++++++++
> 17 files changed, 236 insertions(+), 4 deletions(-)
> create mode 100644 lib/eal/common/eal_common_trace_pmu.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 0e9357f3a3..74cc8fc195 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1850,6 +1850,7 @@ F: doc/guides/prog_guide/eventdev/dispatcher_lib.rst
> PMU - EXPERIMENTAL
> M: Tomasz Duszynski <tduszyn...@marvell.com>
> F: lib/pmu/
> +F: lib/eal/common/eal_common_trace_pmu.c
> F: app/test/test_pmu.c
>
> Job statistics
> diff --git a/app/test/test_trace_perf.c b/app/test/test_trace_perf.c
> index 8257cc02be..28f908ce40 100644
> --- a/app/test/test_trace_perf.c
> +++ b/app/test/test_trace_perf.c
> @@ -114,6 +114,10 @@ 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()
> +#ifdef RTE_LIB_PMU
> +/* 0 corresponds first event passed via --trace= */
> +#define READ_PMU rte_pmu_trace_read(0)
> +#endif
>
> WORKER_DEFINE(GENERIC_VOID)
> WORKER_DEFINE(GENERIC_U64)
> @@ -122,6 +126,9 @@ WORKER_DEFINE(GENERIC_FLOAT)
> WORKER_DEFINE(GENERIC_DOUBLE)
> WORKER_DEFINE(GENERIC_STR)
> WORKER_DEFINE(VOID_FP)
> +#ifdef RTE_LIB_PMU
> +WORKER_DEFINE(READ_PMU)
> +#endif
>
> static void
> run_test(const char *str, lcore_function_t f, struct test_data *data, size_t
> sz)
> @@ -174,6 +181,9 @@ 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);
> +#ifdef RTE_LIB_PMU
> + run_test("read_pmu", worker_fn_READ_PMU, data, sz);
> +#endif
>
> 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 2f47680d5d..362fd20143 100644
> --- a/doc/guides/prog_guide/profile_app.rst
> +++ b/doc/guides/prog_guide/profile_app.rst
> @@ -42,6 +42,11 @@ Current implementation imposes certain limitations:
> * EAL lcores must not share a CPU.
> * Each EAL lcore measures the same group of events.
>
> +Alternatively tracing library can be used,
> +which offers dedicated tracepoint ``rte_pmu_trace_read()``.
> +
> +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 d9b17abe90..97158cce37 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 x86-64 (Intel)
>
> How to add a tracepoint?
> ------------------------
> @@ -139,6 +140,36 @@ 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 Monitoring Unit (PMU) event values can be read from hardware
> registers
> +using the 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_pmu_trace_read(0);
> + rte_pmu_trace_read(1);
> +
> +PMU tracing support must be explicitly enabled
> +using the ``enable_trace_fp`` option for Meson build.
> +
> Event record mode
> -----------------
>
> diff --git a/doc/guides/rel_notes/release_25_07.rst
> b/doc/guides/rel_notes/release_25_07.rst
> index 19be7740c4..3c55f93853 100644
> --- a/doc/guides/rel_notes/release_25_07.rst
> +++ b/doc/guides/rel_notes/release_25_07.rst
> @@ -71,6 +71,8 @@ New Features
>
> Added a Performance Monitoring Unit (PMU) library which allows Linux
> applications
> to perform self monitoring activities without depending on external
> utilities like perf.
> + After integration with :doc:`../prog_guide/trace_lib`, data gathered from
> hardware counters
> + can be stored in CTF format for further analysis.
>
> * **Added Mucse rnp net driver.**
>
> diff --git a/lib/eal/common/eal_common_trace.c
> b/lib/eal/common/eal_common_trace.c
> index be1f78a68d..45e7f9aa56 100644
> --- a/lib/eal/common/eal_common_trace.c
> +++ b/lib/eal/common/eal_common_trace.c
> @@ -75,8 +75,10 @@ eal_trace_init(void)
> goto free_meta;
>
> /* Apply global configurations */
> - STAILQ_FOREACH(arg, &trace.args, next)
> + STAILQ_FOREACH(arg, &trace.args, next) {
> trace_args_apply(arg->val);
> + trace_pmu_args_apply(arg->val);
> + }
>
> rte_trace_mode_set(trace.mode);
>
> @@ -92,6 +94,7 @@ eal_trace_init(void)
> void
> eal_trace_fini(void)
> {
> + trace_pmu_args_free();
> trace_mem_free();
> trace_metadata_destroy();
> eal_trace_args_free();
> diff --git a/lib/eal/common/eal_common_trace_pmu.c
> b/lib/eal/common/eal_common_trace_pmu.c
> new file mode 100644
> index 0000000000..3824904481
> --- /dev/null
> +++ b/lib/eal/common/eal_common_trace_pmu.c
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(C) 2025 Marvell International Ltd.
> + */
> +
> +#include <rte_common.h>
> +
> +#include "eal_trace.h"
> +
> +#ifdef RTE_LIB_PMU
> +
> +#include <rte_pmu.h>
> +
> +void
> +trace_pmu_args_apply(const char *arg)
> +{
> + static bool once;
> +
> + if (!once) {
> + if (rte_pmu_init())
> + return;
> + once = true;
> + }
> +
> + rte_pmu_add_events_by_pattern(arg);
> +}
> +
> +void
> +trace_pmu_args_free(void)
> +{
> + rte_pmu_fini();
> +}
> +
> +#else /* !RTE_LIB_PMU */
> +
> +void trace_pmu_args_apply(const char *arg __rte_unused) { return; }
> +void trace_pmu_args_free(void) { return; }
> +
> +#endif /* RTE_LIB_PMU */
> diff --git a/lib/eal/common/eal_common_trace_points.c
> b/lib/eal/common/eal_common_trace_points.c
> index 0903f3c639..ea90279d77 100644
> --- a/lib/eal/common/eal_common_trace_points.c
> +++ b/lib/eal/common/eal_common_trace_points.c
> @@ -119,3 +119,23 @@ 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)
> +
> +#ifdef RTE_LIB_PMU
> +RTE_EXPORT_EXPERIMENTAL_SYMBOL(__rte_pmu_trace_read, 25.07)
> +RTE_TRACE_POINT_REGISTER(rte_pmu_trace_read,
> + lib.pmu.read)
> +#endif
> +#ifdef RTE_EXEC_ENV_IS_WINDOWS
> +/* gen-version-map.py script generates export symbol maps by scanning source
> files without
> + * evaluating conditional compilation. Hence __rte_pmu_trace_read will be
> included the version map
> + * even if library is not compiled.
> + *
> + * On Windows if msvc linker is used this leads to a hard link error
> + * (LNK2001: unresolved external symbol) because msvc requires all symbols
> listed in the .def file
> + * to be present in the object files.
> + *
> + * Other linkers, e.g: gnu ld or mingw ld, are more forgiving. They silently
> ignore symbols listed
> + * in the map file if those symbols are not present in the binary.
> + */
> +rte_trace_point_t __rte_pmu_trace_read;
> +#endif
>From a quick look, could you export this symbol from the PMU library itself?
--
David Marchand
