RE: [PATCH v4 1/4] eal: add generic support for reading PMU events

[Tomasz Duszynski <tduszynski@marvell.com>]

> -----Original Message-----
> From: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
> Sent: Thursday, December 15, 2022 9:46 AM
> To: Tomasz Duszynski <tduszynski@marvell.com>; dev@dpdk.org
> Cc: thomas@monjalon.net; Jerin Jacob Kollanukkaran <jerinj@marvell.com>; mb@smartsharesystems.com;
> zhoumin@loongson.cn
> Subject: [EXT] Re: [PATCH v4 1/4] eal: add generic support for reading PMU events
> 
> External Email
> 
> ----------------------------------------------------------------------
> On 2022-12-13 11:43, Tomasz Duszynski wrote:
> > Add support for programming PMU counters and reading their values in
> > runtime bypassing kernel completely.
> >
> > This is especially useful in cases where CPU cores are isolated
> > (nohz_full) i.e run dedicated tasks. In such cases one cannot use
> > standard perf utility without sacrificing latency and performance.
> >
> > Signed-off-by: Tomasz Duszynski <tduszynski@marvell.com>
> > ---
> >   app/test/meson.build                  |   1 +
> >   app/test/test_pmu.c                   |  41 +++
> >   doc/guides/prog_guide/profile_app.rst |   8 +
> >   lib/eal/common/meson.build            |   3 +
> >   lib/eal/common/pmu_private.h          |  41 +++
> >   lib/eal/common/rte_pmu.c              | 456 ++++++++++++++++++++++++++
> >   lib/eal/include/meson.build           |   1 +
> >   lib/eal/include/rte_pmu.h             | 204 ++++++++++++
> >   lib/eal/linux/eal.c                   |   4 +
> >   lib/eal/version.map                   |   6 +
> >   10 files changed, 765 insertions(+)
> >   create mode 100644 app/test/test_pmu.c
> >   create mode 100644 lib/eal/common/pmu_private.h
> >   create mode 100644 lib/eal/common/rte_pmu.c
> >   create mode 100644 lib/eal/include/rte_pmu.h
> >
> > diff --git a/app/test/meson.build b/app/test/meson.build index
> > f34d19e3c3..93b3300309 100644
> > --- a/app/test/meson.build
> > +++ b/app/test/meson.build
> > @@ -143,6 +143,7 @@ test_sources = files(
> >           'test_timer_racecond.c',
> >           'test_timer_secondary.c',
> >           'test_ticketlock.c',
> > +        'test_pmu.c',
> >           'test_trace.c',
> >           'test_trace_register.c',
> >           'test_trace_perf.c',
> > diff --git a/app/test/test_pmu.c b/app/test/test_pmu.c new file mode
> > 100644 index 0000000000..fd331af9ee
> > --- /dev/null
> > +++ b/app/test/test_pmu.c
> > @@ -0,0 +1,41 @@
> > +/* SPDX-License-Identifier: BSD-3-Clause
> > + * Copyright(C) 2022 Marvell International Ltd.
> > + */
> > +
> > +#include <rte_pmu.h>
> > +
> > +#include "test.h"
> > +
> > +static int
> > +test_pmu_read(void)
> > +{
> > +	uint64_t val = 0;
> > +	int tries = 10;
> > +	int event = -1;
> > +
> > +	while (tries--)
> > +		val += rte_pmu_read(event);
> > +
> > +	if (val == 0)
> > +		return TEST_FAILED;
> > +
> > +	return TEST_SUCCESS;
> > +}
> > +
> > +static struct unit_test_suite pmu_tests = {
> > +	.suite_name = "pmu autotest",
> > +	.setup = NULL,
> > +	.teardown = NULL,
> > +	.unit_test_cases = {
> > +		TEST_CASE(test_pmu_read),
> > +		TEST_CASES_END()
> > +	}
> > +};
> > +
> > +static int
> > +test_pmu(void)
> > +{
> > +	return unit_test_suite_runner(&pmu_tests);
> > +}
> > +
> > +REGISTER_TEST_COMMAND(pmu_autotest, test_pmu);
> > diff --git a/doc/guides/prog_guide/profile_app.rst
> > b/doc/guides/prog_guide/profile_app.rst
> > index 14292d4c25..a8b501fe0c 100644
> > --- a/doc/guides/prog_guide/profile_app.rst
> > +++ b/doc/guides/prog_guide/profile_app.rst
> > @@ -7,6 +7,14 @@ Profile Your Application
> >   The following sections describe methods of profiling DPDK applications on
> >   different architectures.
> >
> > +Performance counter based profiling
> > +-----------------------------------
> > +
> > +Majority of architectures support some sort hardware measurement unit
> > +which provides a set of programmable counters that monitor specific
> > +events. There are different tools which can gather that information,
> > +perf being an example here. Though in some scenarios, eg. when CPU
> > +cores are 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()``.
> >
> >   Profiling on x86
> >   ----------------
> > diff --git a/lib/eal/common/meson.build b/lib/eal/common/meson.build
> > index 917758cc65..d6d05b56f3 100644
> > --- a/lib/eal/common/meson.build
> > +++ b/lib/eal/common/meson.build
> > @@ -38,6 +38,9 @@ sources += files(
> >           'rte_service.c',
> >           'rte_version.c',
> >   )
> > +if is_linux
> > +    sources += files('rte_pmu.c')
> > +endif
> >   if is_linux or is_windows
> >       sources += files('eal_common_dynmem.c')
> >   endif
> > diff --git a/lib/eal/common/pmu_private.h
> > b/lib/eal/common/pmu_private.h new file mode 100644 index
> > 0000000000..cade4245e6
> > --- /dev/null
> > +++ b/lib/eal/common/pmu_private.h
> > @@ -0,0 +1,41 @@
> > +/* SPDX-License-Identifier: BSD-3-Clause
> > + * Copyright(c) 2022 Marvell
> > + */
> > +
> > +#ifndef _PMU_PRIVATE_H_
> > +#define _PMU_PRIVATE_H_
> > +
> > +/**
> > + * Architecture specific PMU init callback.
> > + *
> > + * @return
> > + *   0 in case of success, negative value otherwise.
> > + */
> > +int
> > +pmu_arch_init(void);
> > +
> > +/**
> > + * Architecture specific PMU cleanup callback.
> > + */
> > +void
> > +pmu_arch_fini(void);
> > +
> > +/**
> > + * Apply architecture specific settings to config before passing it to syscall.
> > + */
> > +void
> > +pmu_arch_fixup_config(uint64_t config[3]);
> > +
> > +/**
> > + * Initialize PMU tracing internals.
> > + */
> > +void
> > +eal_pmu_init(void);
> > +
> > +/**
> > + * Cleanup PMU internals.
> > + */
> > +void
> > +eal_pmu_fini(void);
> > +
> > +#endif /* _PMU_PRIVATE_H_ */
> > diff --git a/lib/eal/common/rte_pmu.c b/lib/eal/common/rte_pmu.c new
> > file mode 100644 index 0000000000..049fe19fe3
> > --- /dev/null
> > +++ b/lib/eal/common/rte_pmu.c
> > @@ -0,0 +1,456 @@
> > +/* SPDX-License-Identifier: BSD-3-Clause
> > + * Copyright(C) 2022 Marvell International Ltd.
> > + */
> > +
> > +#include <ctype.h>
> > +#include <dirent.h>
> > +#include <errno.h>
> > +#include <regex.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <sys/ioctl.h>
> > +#include <sys/mman.h>
> > +#include <sys/queue.h>
> > +#include <sys/syscall.h>
> > +#include <unistd.h>
> > +
> > +#include <rte_eal_paging.h>
> > +#include <rte_pmu.h>
> > +#include <rte_tailq.h>
> > +
> > +#include "pmu_private.h"
> > +
> > +#define EVENT_SOURCE_DEVICES_PATH "/sys/bus/event_source/devices"
> > +
> > +#ifndef GENMASK_ULL
> > +#define GENMASK_ULL(h, l) ((~0ULL - (1ULL << (l)) + 1) & (~0ULL >>
> > +((64 - 1 - (h))))) #endif
> > +
> > +#ifndef FIELD_PREP
> > +#define FIELD_PREP(m, v) (((uint64_t)(v) << (__builtin_ffsll(m) - 1))
> > +& (m)) #endif
> > +
> > +struct rte_pmu *rte_pmu;
> > +
> > +/*
> > + * Following __rte_weak functions provide default no-op.
> > +Architectures should override them if
> > + * necessary.
> > + */
> > +
> > +int
> > +__rte_weak pmu_arch_init(void)
> > +{
> > +	return 0;
> > +}
> > +
> > +void
> > +__rte_weak pmu_arch_fini(void)
> > +{
> > +}
> > +
> > +void
> > +__rte_weak pmu_arch_fixup_config(uint64_t config[3]) {
> > +	RTE_SET_USED(config);
> > +}
> > +
> > +static int
> > +get_term_format(const char *name, int *num, uint64_t *mask) {
> > +	char *config = NULL;
> > +	char path[PATH_MAX];
> > +	int high, low, ret;
> > +	FILE *fp;
> > +
> > +	/* quiesce -Wmaybe-uninitialized warning */
> > +	*num = 0;
> > +	*mask = 0;
> > +
> > +	snprintf(path, sizeof(path), EVENT_SOURCE_DEVICES_PATH
> > +"/%s/format/%s", rte_pmu->name, name)
> 
> This code might crash in case a long name is supplied, which is maybe not want you want. A
> trunacte and a "file not found" is probably better.
> I believe there is a snprintf lookalike with these properties in DPDK.
> 

In scenario, which is pretty unlikely especially because sysfs files have sane names, where 
'path' cannot accommodate the whole string there will be NUL implicitly appended by snprintf.
Hence fopen will fail. Not sure how this may go wrong. 

> > +	fp = fopen(path, "r");
> > +	if (!fp)
> > +		return -errno;
> > +
> > +	errno = 0;
> > +	ret = fscanf(fp, "%m[^:]:%d-%d", &config, &low, &high);
> > +	if (ret < 2) {
> > +		ret = -ENODATA;
> > +		goto out;
> > +	}
> > +	if (errno) {
> > +		ret = -errno;
> > +		goto out;
> > +	}
> > +
> > +	if (ret == 2)
> > +		high = low;
> > +
> > +	*mask = GENMASK_ULL(high, low);
> > +	/* Last digit should be [012]. If last digit is missing 0 is implied. */
> > +	*num = config[strlen(config) - 1];
> > +	*num = isdigit(*num) ? *num - '0' : 0;
> > +
> > +	ret = 0;
> > +out:
> > +	free(config);
> > +	fclose(fp);
> > +
> > +	return ret;
> > +}
> > +
> > +static int
> > +parse_event(char *buf, uint64_t config[3]) {
> > +	char *token, *term;
> > +	int num, ret, val;
> > +	uint64_t mask;
> > +
> > +	config[0] = config[1] = config[2] = 0;
> > +
> > +	token = strtok(buf, ",");
> > +	while (token) {
> > +		errno = 0;
> > +		/* <term>=<value> */
> > +		ret = sscanf(token, "%m[^=]=%i", &term, &val);
> > +		if (ret < 1)
> > +			return -ENODATA;
> > +		if (errno)
> > +			return -errno;
> > +		if (ret == 1)
> > +			val = 1;
> > +
> > +		ret = get_term_format(term, &num, &mask);
> > +		free(term);
> > +		if (ret)
> > +			return ret;
> > +
> > +		config[num] |= FIELD_PREP(mask, val);
> > +		token = strtok(NULL, ",");
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int
> > +get_event_config(const char *name, uint64_t config[3]) {
> > +	char path[PATH_MAX], buf[BUFSIZ];
> > +	FILE *fp;
> > +	int ret;
> > +
> > +	snprintf(path, sizeof(path), EVENT_SOURCE_DEVICES_PATH "/%s/events/%s", rte_pmu->name,
> name);
> > +	fp = fopen(path, "r");
> > +	if (!fp)
> > +		return -errno;
> > +
> > +	ret = fread(buf, 1, sizeof(buf), fp);
> > +	if (ret == 0) {
> > +		fclose(fp);
> > +
> > +		return -EINVAL;
> > +	}
> > +	fclose(fp);
> > +	buf[ret] = '\0';
> > +
> > +	return parse_event(buf, config);
> > +}
> > +
> > +static int
> > +do_perf_event_open(uint64_t config[3], int lcore_id, int group_fd) {
> > +	struct perf_event_attr attr = {
> > +		.size = sizeof(struct perf_event_attr),
> > +		.type = PERF_TYPE_RAW,
> > +		.exclude_kernel = 1,
> > +		.exclude_hv = 1,
> > +		.disabled = 1,
> > +	};
> > +
> > +	pmu_arch_fixup_config(config);
> > +
> > +	attr.config = config[0];
> > +	attr.config1 = config[1];
> > +	attr.config2 = config[2];
> > +
> > +	return syscall(SYS_perf_event_open, &attr, rte_gettid(), rte_lcore_to_cpu_id(lcore_id),
> > +		       group_fd, 0);
> > +}
> > +
> > +static int
> > +open_events(int lcore_id)
> > +{
> > +	struct rte_pmu_event_group *group = &rte_pmu->group[lcore_id];
> > +	struct rte_pmu_event *event;
> > +	uint64_t config[3];
> > +	int num = 0, ret;
> > +
> > +	/* group leader gets created first, with fd = -1 */
> > +	group->fds[0] = -1;
> > +
> > +	TAILQ_FOREACH(event, &rte_pmu->event_list, next) {
> > +		ret = get_event_config(event->name, config);
> > +		if (ret) {
> > +			RTE_LOG(ERR, EAL, "failed to get %s event config\n", event->name);
> > +			continue;
> > +		}
> > +
> > +		ret = do_perf_event_open(config, lcore_id, group->fds[0]);
> > +		if (ret == -1) {
> > +			if (errno == EOPNOTSUPP)
> > +				RTE_LOG(ERR, EAL, "64 bit counters not supported\n");
> > +
> > +			ret = -errno;
> > +			goto out;
> > +		}
> > +
> > +		group->fds[event->index] = ret;
> > +		num++;
> > +	}
> > +
> > +	return 0;
> > +out:
> > +	for (--num; num >= 0; num--) {
> > +		close(group->fds[num]);
> > +		group->fds[num] = -1;
> > +	}
> > +
> > +
> > +	return ret;
> > +}
> > +
> > +static int
> > +mmap_events(int lcore_id)
> > +{
> > +	struct rte_pmu_event_group *group = &rte_pmu->group[lcore_id];
> > +	void *addr;
> > +	int ret, i;
> > +
> > +	for (i = 0; i < rte_pmu->num_group_events; i++) {
> > +		addr = mmap(0, rte_mem_page_size(), PROT_READ, MAP_SHARED, group->fds[i], 0);
> > +		if (addr == MAP_FAILED) {
> > +			ret = -errno;
> > +			goto out;
> > +		}
> > +
> > +		group->mmap_pages[i] = addr;
> > +	}
> > +
> > +	return 0;
> > +out:
> > +	for (; i; i--) {
> > +		munmap(group->mmap_pages[i - 1], rte_mem_page_size());
> > +		group->mmap_pages[i - 1] = NULL;
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static void
> > +cleanup_events(int lcore_id)
> 
> lcore_id is an unsigned int.
> 

True, unsigned seems to be more common. 

> > +{
> > +	struct rte_pmu_event_group *group = &rte_pmu->group[lcore_id];
> > +	int i;
> > +
> > +	if (!group->fds)
> > +		return;
> 
> group->fds == NULL
> 
> This coding style violating appears throughput the patch set.
> 

Good point. 

> > +
> > +	if (group->fds[0] != -1)
> > +		ioctl(group->fds[0], PERF_EVENT_IOC_DISABLE, PERF_IOC_FLAG_GROUP);
> > +
> > +	for (i = 0; i < rte_pmu->num_group_events; i++) {
> > +		if (group->mmap_pages[i]) {
> > +			munmap(group->mmap_pages[i], rte_mem_page_size());
> > +			group->mmap_pages[i] = NULL;
> > +		}
> > +
> > +		if (group->fds[i] != -1) {
> > +			close(group->fds[i]);
> > +			group->fds[i] = -1;
> > +		}
> > +	}
> > +
> > +	free(group->mmap_pages);
> > +	free(group->fds);
> > +
> > +	group->mmap_pages = NULL;
> > +	group->fds = NULL;
> > +	group->enabled = false;
> > +}
> > +
> > +int __rte_noinline
> > +rte_pmu_enable_group(int lcore_id)
> 
> unsigned
> 
> > +{
> > +	struct rte_pmu_event_group *group = &rte_pmu->group[lcore_id];
> > +	int ret;
> > +
> > +	if (rte_pmu->num_group_events == 0) {
> > +		RTE_LOG(DEBUG, EAL, "no matching PMU events\n");
> > +
> > +		return 0;
> > +	}
> > +
> > +	group->fds = calloc(rte_pmu->num_group_events, sizeof(*group->fds));
> > +	if (!group->fds) {
> > +		RTE_LOG(ERR, EAL, "failed to alloc descriptor memory\n");
> > +
> > +		return -ENOMEM;
> > +	}
> > +
> > +	group->mmap_pages = calloc(rte_pmu->num_group_events, sizeof(*group->mmap_pages));
> > +	if (!group->mmap_pages) {
> > +		RTE_LOG(ERR, EAL, "failed to alloc userpage memory\n");
> > +
> > +		ret = -ENOMEM;
> > +		goto out;
> > +	}
> > +
> > +	ret = open_events(lcore_id);
> > +	if (ret) {
> > +		RTE_LOG(ERR, EAL, "failed to open events on lcore-worker-%d\n", lcore_id);
> > +		goto out;
> > +	}
> > +
> > +	ret = mmap_events(lcore_id);
> > +	if (ret) {
> > +		RTE_LOG(ERR, EAL, "failed to map events on lcore-worker-%d\n", lcore_id);
> > +		goto out;
> > +	}
> > +
> > +	if (ioctl(group->fds[0], PERF_EVENT_IOC_ENABLE, PERF_IOC_FLAG_GROUP) == -1) {
> > +		RTE_LOG(ERR, EAL, "failed to enable events on lcore-worker-%d\n",
> > +lcore_id);
> > +
> > +		ret = -errno;
> > +		goto out;
> > +	}
> > +
> > +	return 0;
> > +
> > +out:
> > +	cleanup_events(lcore_id);
> > +
> > +	return ret;
> > +}
> > +
> > +static int
> > +scan_pmus(void)
> > +{
> > +	char path[PATH_MAX];
> > +	struct dirent *dent;
> > +	const char *name;
> > +	DIR *dirp;
> > +
> > +	dirp = opendir(EVENT_SOURCE_DEVICES_PATH);
> > +	if (!dirp)
> > +		return -errno;
> > +
> > +	while ((dent = readdir(dirp))) {
> > +		name = dent->d_name;
> > +		if (name[0] == '.')
> > +			continue;
> > +
> > +		/* sysfs entry should either contain cpus or be a cpu */
> > +		if (!strcmp(name, "cpu"))
> > +			break;
> > +
> > +		snprintf(path, sizeof(path), EVENT_SOURCE_DEVICES_PATH "/%s/cpus", name);
> > +		if (access(path, F_OK) == 0)
> > +			break;
> > +	}
> > +
> > +	closedir(dirp);
> > +
> > +	if (dent) {
> > +		rte_pmu->name = strdup(name);
> > +		if (!rte_pmu->name)
> > +			return -ENOMEM;
> > +	}
> > +
> > +	return rte_pmu->name ? 0 : -ENODEV;
> > +}
> > +
> > +int
> > +rte_pmu_add_event(const char *name)
> > +{
> > +	struct rte_pmu_event *event;
> > +	char path[PATH_MAX];
> > +
> > +	snprintf(path, sizeof(path), EVENT_SOURCE_DEVICES_PATH "/%s/events/%s", rte_pmu->name,
> name);
> > +	if (access(path, R_OK))
> > +		return -ENODEV;
> > +
> > +	TAILQ_FOREACH(event, &rte_pmu->event_list, next) {
> > +		if (!strcmp(event->name, name))
> > +			return event->index;
> > +		continue;
> > +	}
> > +
> > +	event = calloc(1, sizeof(*event));
> > +	if (!event)
> > +		return -ENOMEM;
> > +
> > +	event->name = strdup(name);
> > +	if (!event->name) {
> > +		free(event);
> > +
> > +		return -ENOMEM;
> > +	}
> > +
> > +	event->index = rte_pmu->num_group_events++;
> > +	TAILQ_INSERT_TAIL(&rte_pmu->event_list, event, next);
> > +
> > +	RTE_LOG(DEBUG, EAL, "%s even added at index %d\n", name,
> > +event->index);
> > +
> > +	return event->index;
> > +}
> > +
> > +void
> > +eal_pmu_init(void)
> > +{
> > +	int ret;
> > +
> > +	rte_pmu = calloc(1, sizeof(*rte_pmu));
> > +	if (!rte_pmu) {
> > +		RTE_LOG(ERR, EAL, "failed to alloc PMU\n");
> > +
> > +		return;
> > +	}
> > +
> > +	TAILQ_INIT(&rte_pmu->event_list);
> > +
> > +	ret = scan_pmus();
> > +	if (ret) {
> > +		RTE_LOG(ERR, EAL, "failed to find core pmu\n");
> > +		goto out;
> > +	}
> > +
> > +	ret = pmu_arch_init();
> > +	if (ret) {
> > +		RTE_LOG(ERR, EAL, "failed to setup arch for PMU\n");
> > +		goto out;
> > +	}
> > +
> > +	return;
> > +out:
> > +	free(rte_pmu->name);
> > +	free(rte_pmu);
> > +}
> > +
> > +void
> > +eal_pmu_fini(void)
> > +{
> > +	struct rte_pmu_event *event, *tmp;
> > +	int lcore_id;
> > +
> > +	RTE_TAILQ_FOREACH_SAFE(event, &rte_pmu->event_list, next, tmp) {
> > +		TAILQ_REMOVE(&rte_pmu->event_list, event, next);
> > +		free(event->name);
> > +		free(event);
> > +	}
> > +
> > +	RTE_LCORE_FOREACH_WORKER(lcore_id)
> > +		cleanup_events(lcore_id);
> 
> Why is the main lcore left out?
> 

Main lcore was omitted because it's pretty uncommon for it to do a heavy-lifting so
usefulness of reading counters is questionable. It can be added for completeness
though. 

Do you have any specific use case on your mind?

> > +
> > +	pmu_arch_fini();
> > +	free(rte_pmu->name);
> > +	free(rte_pmu);
> > +}
> > diff --git a/lib/eal/include/meson.build b/lib/eal/include/meson.build
> > index cfcd40aaed..3bf830adee 100644
> > --- a/lib/eal/include/meson.build
> > +++ b/lib/eal/include/meson.build
> > @@ -36,6 +36,7 @@ headers += files(
> >           'rte_pci_dev_features.h',
> >           'rte_per_lcore.h',
> >           'rte_pflock.h',
> > +        'rte_pmu.h',
> >           'rte_random.h',
> >           'rte_reciprocal.h',
> >           'rte_seqcount.h',
> > diff --git a/lib/eal/include/rte_pmu.h b/lib/eal/include/rte_pmu.h new
> > file mode 100644 index 0000000000..e4b4f6b052
> > --- /dev/null
> > +++ b/lib/eal/include/rte_pmu.h
> > @@ -0,0 +1,204 @@
> > +/* SPDX-License-Identifier: BSD-3-Clause
> > + * Copyright(c) 2022 Marvell
> > + */
> > +
> > +#ifndef _RTE_PMU_H_
> > +#define _RTE_PMU_H_
> > +
> > +#ifdef __cplusplus
> > +extern "C" {
> > +#endif
> > +
> > +#include <rte_common.h>
> > +#include <rte_compat.h>
> > +
> > +#ifdef RTE_EXEC_ENV_LINUX
> > +
> > +#include <linux/perf_event.h>
> > +
> > +#include <rte_atomic.h>
> > +#include <rte_branch_prediction.h>
> > +#include <rte_lcore.h>
> > +#include <rte_log.h>
> > +
> > +/**
> > + * @file
> > + *
> > + * PMU event tracing operations
> > + *
> > + * This file defines generic API and types necessary to setup PMU and
> > + * read selected counters in runtime.
> > + */
> > +
> > +/**
> > + * A structure describing a group of events.
> > + */
> > +struct rte_pmu_event_group {
> > +	int *fds; /**< array of event descriptors */
> > +	void **mmap_pages; /**< array of pointers to mmapped perf_event_attr structures */
> > +	bool enabled; /**< true if group was enabled on particular lcore */
> > +};
> > +
> > +/**
> > + * A structure describing an event.
> > + */
> > +struct rte_pmu_event {
> > +	char *name; /** name of an event */
> > +	int index; /** event index into fds/mmap_pages */
> > +	TAILQ_ENTRY(rte_pmu_event) next; /** list entry */ };
> > +
> > +/**
> > + * A PMU state container.
> > + */
> > +struct rte_pmu {
> > +	char *name; /** name of core PMU listed under /sys/bus/event_source/devices */
> > +	struct rte_pmu_event_group group[RTE_MAX_LCORE]; /**< per lcore event group data */
> > +	int num_group_events; /**< number of events in a group */
> > +	TAILQ_HEAD(, rte_pmu_event) event_list; /**< list of matching events
> > +*/ };
> > +
> > +/** Pointer to the PMU state container */ extern struct rte_pmu
> > +*rte_pmu;
> > +
> > +/** Each architecture supporting PMU needs to provide its own version
> > +*/ #ifndef rte_pmu_pmc_read #define rte_pmu_pmc_read(index) ({ 0; })
> > +#endif
> > +
> > +/**
> > + * @internal
> > + *
> > + * Read PMU counter.
> > + *
> > + * @param pc
> > + *   Pointer to the mmapped user page.
> > + * @return
> > + *   Counter value read from hardware.
> > + */
> > +__rte_internal
> > +static __rte_always_inline uint64_t
> > +rte_pmu_read_userpage(struct perf_event_mmap_page *pc) {
> > +	uint64_t offset, width, pmc = 0;
> > +	uint32_t seq, index;
> > +	int tries = 100;
> > +
> > +	for (;;) {
> > +		seq = pc->lock;
> > +		rte_compiler_barrier();
> > +		index = pc->index;
> > +		offset = pc->offset;
> > +		width = pc->pmc_width;
> > +
> > +		if (likely(pc->cap_user_rdpmc && index)) {
> > +			pmc = rte_pmu_pmc_read(index - 1);
> > +			pmc <<= 64 - width;
> > +			pmc >>= 64 - width;
> > +		}
> > +
> > +		rte_compiler_barrier();
> > +
> > +		if (likely(pc->lock == seq))
> > +			return pmc + offset;
> > +
> > +		if (--tries == 0) {
> > +			RTE_LOG(DEBUG, EAL, "failed to get perf_event_mmap_page lock\n");
> > +			break;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * @internal
> > + *
> > + * Enable group of events for a given lcore.
> > + *
> > + * @param lcore_id
> > + *   The identifier of the lcore.
> > + * @return
> > + *   0 in case of success, negative value otherwise.
> > + */
> > +__rte_internal
> > +int
> > +rte_pmu_enable_group(int lcore_id);
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change without prior notice
> > + *
> > + * Add event to the group of enabled events.
> > + *
> > + * @param name
> > + *   Name of an event listed under /sys/bus/event_source/devices/pmu/events.
> > + * @return
> > + *   Event index in case of success, negative value otherwise.
> > + */
> > +__rte_experimental
> > +int
> > +rte_pmu_add_event(const char *name);
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change without prior notice
> > + *
> > + * Read hardware counter configured to count occurrences of an event.
> > + *
> > + * @param index
> > + *   Index of an event to be read.
> > + * @return
> > + *   Event value read from register. In case of errors or lack of support
> > + *   0 is returned. In other words, stream of zeros in a trace file
> > + *   indicates problem with reading particular PMU event register.
> > + */
> > +__rte_experimental
> > +static __rte_always_inline uint64_t
> > +rte_pmu_read(int index)
> > +{
> > +	int lcore_id = rte_lcore_id();
> > +	struct rte_pmu_event_group *group;
> > +	int ret;
> > +
> > +	if (!rte_pmu)
> > +		return 0;
> > +
> > +	group = &rte_pmu->group[lcore_id];
> > +	if (!group->enabled) {
> > +		ret = rte_pmu_enable_group(lcore_id);
> > +		if (ret)
> > +			return 0;
> > +
> > +		group->enabled = true;
> > +	}
> > +
> > +	if (index < 0 || index >= rte_pmu->num_group_events)
> > +		return 0;
> > +
> > +	return rte_pmu_read_userpage((struct perf_event_mmap_page
> > +*)group->mmap_pages[index]); }
> > +
> > +#else /* !RTE_EXEC_ENV_LINUX */
> > +
> > +__rte_experimental
> > +static int __rte_unused
> > +rte_pmu_add_event(__rte_unused const char *name) {
> > +	return -1;
> > +}
> > +
> > +__rte_experimental
> > +static __rte_always_inline uint64_t
> > +rte_pmu_read(__rte_unused int index)
> > +{
> > +	return 0;
> > +}
> > +
> > +#endif /* RTE_EXEC_ENV_LINUX */
> > +
> > +#ifdef __cplusplus
> > +}
> > +#endif
> > +
> > +#endif /* _RTE_PMU_H_ */
> > diff --git a/lib/eal/linux/eal.c b/lib/eal/linux/eal.c index
> > 8c118d0d9f..751a13b597 100644
> > --- a/lib/eal/linux/eal.c
> > +++ b/lib/eal/linux/eal.c
> > @@ -53,6 +53,7 @@
> >   #include "eal_options.h"
> >   #include "eal_vfio.h"
> >   #include "hotplug_mp.h"
> > +#include "pmu_private.h"
> >
> >   #define MEMSIZE_IF_NO_HUGE_PAGE (64ULL * 1024ULL * 1024ULL)
> >
> > @@ -1206,6 +1207,8 @@ rte_eal_init(int argc, char **argv)
> >   		return -1;
> >   	}
> >
> > +	eal_pmu_init();
> > +
> >   	if (rte_eal_tailqs_init() < 0) {
> >   		rte_eal_init_alert("Cannot init tail queues for objects");
> >   		rte_errno = EFAULT;
> > @@ -1372,6 +1375,7 @@ rte_eal_cleanup(void)
> >   	eal_bus_cleanup();
> >   	rte_trace_save();
> >   	eal_trace_fini();
> > +	eal_pmu_fini();
> >   	/* after this point, any DPDK pointers will become dangling */
> >   	rte_eal_memory_detach();
> >   	eal_mp_dev_hotplug_cleanup();
> > diff --git a/lib/eal/version.map b/lib/eal/version.map index
> > 7ad12a7dc9..9225f46f67 100644
> > --- a/lib/eal/version.map
> > +++ b/lib/eal/version.map
> > @@ -440,6 +440,11 @@ EXPERIMENTAL {
> >   	rte_thread_detach;
> >   	rte_thread_equal;
> >   	rte_thread_join;
> > +
> > +	# added in 23.03
> > +	rte_pmu; # WINDOWS_NO_EXPORT
> > +	rte_pmu_add_event; # WINDOWS_NO_EXPORT
> > +	rte_pmu_read; # WINDOWS_NO_EXPORT
> >   };
> >
> >   INTERNAL {
> > @@ -483,4 +488,5 @@ INTERNAL {
> >   	rte_mem_map;
> >   	rte_mem_page_size;
> >   	rte_mem_unmap;
> > +	rte_pmu_enable_group;
> >   };