[PATCH v15 1/4] lib: add generic support for reading PMU events
Tomasz Duszynski
tduszynski at marvell.com
Fri Nov 15 11:20:53 CET 2024
>-----Original Message-----
>From: Konstantin Ananyev <konstantin.ananyev at huawei.com>
>Sent: Tuesday, November 5, 2024 11:58 AM
>To: Tomasz Duszynski <tduszynski at marvell.com>; Thomas Monjalon <thomas at monjalon.net>
>Cc: Ruifeng.Wang at arm.com; bruce.richardson at intel.com; david.marchand at redhat.com; dev at dpdk.org;
>Jerin Jacob <jerinj at marvell.com>; konstantin.v.ananyev at yandex.ru; mattias.ronnblom at ericsson.com;
>mb at smartsharesystems.com; roretzla at linux.microsoft.com; stephen at networkplumber.org;
>zhoumin at loongson.cn
>Subject: [EXTERNAL] RE: [PATCH v15 1/4] lib: add generic support for reading PMU events
>
>> 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 > i. e run dedicated tasks. In such
>> cases one cannot
>
>
>
>> 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 i.e
>> run dedicated tasks. In such cases one cannot use standard perf
>> utility without sacrificing latency and performance.
>
>LGTM in general, just few questions, nits - majority about docs/comments.
>
>> Signed-off-by: Tomasz Duszynski <tduszynski at marvell.com>
>> ---
>> MAINTAINERS | 5 +
>> app/test/meson.build | 1 +
>> app/test/test_pmu.c | 49 +++
>> doc/api/doxy-api-index.md | 3 +-
>> doc/api/doxy-api.conf.in | 1 +
>> doc/guides/prog_guide/profile_app.rst | 29 ++
>> doc/guides/rel_notes/release_24_11.rst | 7 +
>> lib/eal/meson.build | 3 +
>> lib/meson.build | 1 +
>> lib/pmu/meson.build | 13 +
>> lib/pmu/pmu_private.h | 32 ++
>> lib/pmu/rte_pmu.c | 473 +++++++++++++++++++++++++
>> lib/pmu/rte_pmu.h | 205 +++++++++++
>> lib/pmu/version.map | 13 +
>> 14 files changed, 834 insertions(+), 1 deletion(-) create mode
>> 100644 app/test/test_pmu.c create mode 100644 lib/pmu/meson.build
>> create mode 100644 lib/pmu/pmu_private.h create mode 100644
>> lib/pmu/rte_pmu.c create mode 100644 lib/pmu/rte_pmu.h create mode
>> 100644 lib/pmu/version.map
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS index cd78bc7db1..077efe41cf
>> 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -1816,6 +1816,11 @@ M: Nithin Dabilpuram <ndabilpuram at marvell.com>
>> M: Pavan Nikhilesh <pbhagavatula at marvell.com>
>> F: lib/node/
>>
>> +PMU - EXPERIMENTAL
>> +M: Tomasz Duszynski <tduszynski at marvell.com>
>> +F: lib/pmu/
>> +F: app/test/test_pmu*
>> +
>>
>> Test Applications
>> -----------------
>> diff --git a/app/test/meson.build b/app/test/meson.build index
>> 0f7e11969a..5f1622ecab 100644
>> --- a/app/test/meson.build
>> +++ b/app/test/meson.build
>> @@ -141,6 +141,7 @@ source_file_deps = {
>> 'test_pmd_perf.c': ['ethdev', 'net'] + packet_burst_generator_deps,
>> 'test_pmd_ring.c': ['net_ring', 'ethdev', 'bus_vdev'],
>> 'test_pmd_ring_perf.c': ['ethdev', 'net_ring', 'bus_vdev'],
>> + 'test_pmu.c': ['pmu'],
>> 'test_power.c': ['power'],
>> 'test_power_cpufreq.c': ['power'],
>> 'test_power_intel_uncore.c': ['power'], diff --git
>> a/app/test/test_pmu.c b/app/test/test_pmu.c new file mode 100644 index
>> 0000000000..464e5068ec
>> --- /dev/null
>> +++ b/app/test/test_pmu.c
>> @@ -0,0 +1,49 @@
>> +/* SPDX-License-Identifier: BSD-3-Clause
>> + * Copyright(C) 2024 Marvell International Ltd.
>> + */
>> +
>> +#include <rte_pmu.h>
>> +
>> +#include "test.h"
>> +
>> +static int
>> +test_pmu_read(void)
>> +{
>> + const char *name = NULL;
>> + int tries = 10, event;
>> + uint64_t val = 0;
>> +
>> + if (name == NULL) {
>> + printf("PMU not supported on this arch\n");
>> + return TEST_SKIPPED;
>> + }
>> +
>> + if (rte_pmu_init() < 0)
>> + return TEST_FAILED;
>> +
>> + event = rte_pmu_add_event(name);
>> + while (tries--)
>> + val += rte_pmu_read(event);
>> +
>> + rte_pmu_fini();
>> +
>> + return val ? TEST_SUCCESS : TEST_FAILED; }
>> +
>> +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_FAST_TEST(pmu_autotest, true, true, test_pmu);
>> diff --git a/doc/api/doxy-api-index.md b/doc/api/doxy-api-index.md
>> index 266c8b90dc..3e6020f367 100644
>> --- a/doc/api/doxy-api-index.md
>> +++ b/doc/api/doxy-api-index.md
>> @@ -240,7 +240,8 @@ The public API headers are grouped by topics:
>> [log](@ref rte_log.h),
>> [errno](@ref rte_errno.h),
>> [trace](@ref rte_trace.h),
>> - [trace_point](@ref rte_trace_point.h)
>> + [trace_point](@ref rte_trace_point.h), [pmu](@ref rte_pmu.h)
>>
>> - **misc**:
>> [EAL config](@ref rte_eal.h),
>> diff --git a/doc/api/doxy-api.conf.in b/doc/api/doxy-api.conf.in index
>> c94f02d411..f4b382e073 100644
>> --- a/doc/api/doxy-api.conf.in
>> +++ b/doc/api/doxy-api.conf.in
>> @@ -69,6 +69,7 @@ INPUT = @TOPDIR@/doc/api/doxy-api-index.md \
>> @TOPDIR@/lib/pdcp \
>> @TOPDIR@/lib/pdump \
>> @TOPDIR@/lib/pipeline \
>> + @TOPDIR@/lib/pmu \
>> @TOPDIR@/lib/port \
>> @TOPDIR@/lib/power \
>> @TOPDIR@/lib/ptr_compress \ diff --git
>> a/doc/guides/prog_guide/profile_app.rst
>> b/doc/guides/prog_guide/profile_app.rst
>> index a6b5fb4d5e..854c515a61 100644
>> --- a/doc/guides/prog_guide/profile_app.rst
>> +++ b/doc/guides/prog_guide/profile_app.rst
>> @@ -7,6 +7,35 @@ Profile Your Application The following sections
>> describe methods of profiling DPDK applications on different
>> architectures.
>>
>> +Performance counter based profiling
>> +-----------------------------------
>> +
>> +Majority of architectures support some performance monitoring unit (PMU).
>> +Such unit provides programmable counters that monitor specific events.
>> +
>> +Different tools gather that information, like for example perf.
>> +However, in some scenarios when CPU cores are isolated and run
>> +dedicated tasks interrupting those tasks with perf may be undesirable.
>> +
>> +In such cases, an application can use the PMU library to read such events via
>``rte_pmu_read()``.
>> +
>> +By default, userspace applications are not allowed to access PMU
>> +internals. That can be changed by setting
>> +``/sys/kernel/perf_event_paranoid`` to 2 (that should be a default
>> +value anyway) and adding ``CAP_PERFMON`` capability to DPDK
>> +application. Please refer to ``Documentation/admin-guide/perf-security.rst`` under Linux sources
>for more information. Fairly recent kernel, i.e >= 5.9, is advised too.
>> +
>> +As of now implementation imposes certain limitations:
>> +
>> +* Management APIs that normally return a non-negative value will
>> +return error (``-ENOTSUP``) while
>> + ``rte_pmu_read()`` will return ``UINT64_MAX`` if running under unsupported operating system.
>> +
>> +* Only EAL lcores are supported
>> +
>> +* EAL lcores must not share a cpu
>> +
>> +* Each EAL lcore measures same group of events
>> +
>>
>> Profiling on x86
>> ----------------
>> diff --git a/doc/guides/rel_notes/release_24_11.rst
>> b/doc/guides/rel_notes/release_24_11.rst
>> index fa4822d928..d34ecb55e0 100644
>> --- a/doc/guides/rel_notes/release_24_11.rst
>> +++ b/doc/guides/rel_notes/release_24_11.rst
>> @@ -247,6 +247,13 @@ New Features
>> Added ability for node to advertise and update multiple xstat counters,
>> that can be retrieved using ``rte_graph_cluster_stats_get``.
>>
>> +* **Added PMU library.**
>> +
>> + Added a new performance monitoring unit (PMU) library which allows
>> + 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.
>> +
>>
>> Removed Items
>> -------------
>> diff --git a/lib/eal/meson.build b/lib/eal/meson.build index
>> e1d6c4cf17..1349624653 100644
>> --- a/lib/eal/meson.build
>> +++ b/lib/eal/meson.build
>> @@ -18,6 +18,9 @@ deps += ['log', 'kvargs'] if not is_windows
>> deps += ['telemetry']
>> endif
>> +if dpdk_conf.has('RTE_LIB_PMU')
>> + deps += ['pmu']
>> +endif
>> if dpdk_conf.has('RTE_USE_LIBBSD')
>> ext_deps += libbsd
>> endif
>> diff --git a/lib/meson.build b/lib/meson.build index
>> ce92cb5537..968ad29e8d 100644
>> --- a/lib/meson.build
>> +++ b/lib/meson.build
>> @@ -13,6 +13,7 @@ libraries = [
>> 'kvargs', # eal depends on kvargs
>> 'argparse',
>> 'telemetry', # basic info querying
>> + 'pmu',
>> 'eal', # everything depends on eal
>> 'ptr_compress',
>> 'ring',
>> diff --git a/lib/pmu/meson.build b/lib/pmu/meson.build new file mode
>> 100644 index 0000000000..f173b6f55c
>> --- /dev/null
>> +++ b/lib/pmu/meson.build
>> @@ -0,0 +1,13 @@
>> +# SPDX-License-Identifier: BSD-3-Clause # Copyright(C) 2024 Marvell
>> +International Ltd.
>> +
>> +if not is_linux
>> + build = false
>> + reason = 'only supported on Linux'
>> + subdir_done()
>> +endif
>> +
>> +headers = files('rte_pmu.h')
>> +sources = files('rte_pmu.c')
>> +
>> +deps += ['log']
>> diff --git a/lib/pmu/pmu_private.h b/lib/pmu/pmu_private.h new file
>> mode 100644 index 0000000000..d2b15615bf
>> --- /dev/null
>> +++ b/lib/pmu/pmu_private.h
>> @@ -0,0 +1,32 @@
>> +/* SPDX-License-Identifier: BSD-3-Clause
>> + * Copyright(c) 2024 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.
>> + *
>> + * @param config
>> + * Architecture specific event configuration. Consult kernel sources for available options.
>> + */
>> +void
>> +pmu_arch_fixup_config(uint64_t config[3]);
>> +
>> +#endif /* _PMU_PRIVATE_H_ */
>> diff --git a/lib/pmu/rte_pmu.c b/lib/pmu/rte_pmu.c new file mode
>> 100644 index 0000000000..dd57961627
>> --- /dev/null
>> +++ b/lib/pmu/rte_pmu.c
>> @@ -0,0 +1,473 @@
>> +/* SPDX-License-Identifier: BSD-3-Clause
>> + * Copyright(C) 2024 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_atomic.h>
>> +#include <rte_bitops.h>
>> +#include <rte_lcore.h>
>> +#include <rte_log.h>
>> +#include <rte_per_lcore.h>
>> +#include <rte_pmu.h>
>> +#include <rte_tailq.h>
>> +
>> +#include "pmu_private.h"
>> +
>> +#define EVENT_SOURCE_DEVICES_PATH "/sys/bus/event_source/devices"
>> +
>> +#define FIELD_PREP(m, v) (((uint64_t)(v) << (__builtin_ffsll(m) - 1))
>> +& (m))
>> +
>> +RTE_LOG_REGISTER_DEFAULT(rte_pmu_logtype, INFO) #define
>> +RTE_LOGTYPE_PMU rte_pmu_logtype
>> +
>> +#define PMU_LOG(level, ...) \
>> + RTE_LOG_LINE(level, PMU, ## __VA_ARGS__)
>> +
>> +/* A structure describing an event */ struct rte_pmu_event {
>> + char *name;
>> + unsigned int index;
>> + TAILQ_ENTRY(rte_pmu_event) next;
>> +};
>> +
>> +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 __rte_unused config[3]) { }
>> +
>> +static int
>> +get_term_format(const char *name, int *num, uint64_t *mask) {
>> + char path[PATH_MAX];
>> + char *config = NULL;
>> + int high, low, ret;
>> + FILE *fp;
>> +
>> + *num = *mask = 0;
>> + snprintf(path, sizeof(path), EVENT_SOURCE_DEVICES_PATH "/%s/format/%s", rte_pmu.name, name);
>> + fp = fopen(path, "r");
>> + if (fp == NULL)
>> + 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 = RTE_GENMASK64(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 == NULL)
>> + 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 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,
>> + .pinned = group_fd == -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, 0, -1, group_fd, 0); }
>> +
>> +static int
>> +open_events(struct rte_pmu_event_group *group) {
>> + 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)
>> + continue;
>> +
>> + ret = do_perf_event_open(config, group->fds[0]);
>> + if (ret == -1) {
>> + 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(struct rte_pmu_event_group *group) {
>> + long page_size = sysconf(_SC_PAGE_SIZE);
>> + unsigned int i;
>> + void *addr;
>> + int ret;
>> +
>> + for (i = 0; i < rte_pmu.num_group_events; i++) {
>> + addr = mmap(0, 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], page_size);
>> + group->mmap_pages[i - 1] = NULL;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +static void
>> +cleanup_events(struct rte_pmu_event_group *group) {
>> + unsigned int i;
>> +
>> + 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], sysconf(_SC_PAGE_SIZE));
>> + group->mmap_pages[i] = NULL;
>> + }
>> +
>> + if (group->fds[i] != -1) {
>> + close(group->fds[i]);
>> + group->fds[i] = -1;
>> + }
>> + }
>> +
>> + group->enabled = false;
>> +}
>> +
>> +int
>> +__rte_pmu_enable_group(struct rte_pmu_event_group *group) {
>> + int ret;
>> +
>> + if (rte_pmu.num_group_events == 0)
>> + return -ENODEV;
>> +
>> + ret = open_events(group);
>> + if (ret)
>> + goto out;
>> +
>> + ret = mmap_events(group);
>> + if (ret)
>> + goto out;
>> +
>> + if (ioctl(group->fds[0], PERF_EVENT_IOC_RESET, PERF_IOC_FLAG_GROUP) == -1) {
>> + ret = -errno;
>> + goto out;
>> + }
>> +
>> + if (ioctl(group->fds[0], PERF_EVENT_IOC_ENABLE, PERF_IOC_FLAG_GROUP) == -1) {
>> + ret = -errno;
>> + goto out;
>> + }
>> +
>> + group->enabled = true;
>> +
>> + return 0;
>> +out:
>> + cleanup_events(group);
>> +
>> + 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 == NULL)
>> + 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;
>> + }
>> +
>> + if (dent) {
>> + rte_pmu.name = strdup(name);
>> + if (rte_pmu.name == NULL) {
>> + closedir(dirp);
>> +
>> + return -ENOMEM;
>> + }
>> + }
>> +
>> + closedir(dirp);
>> +
>> + return rte_pmu.name ? 0 : -ENODEV;
>> +}
>> +
>> +static struct rte_pmu_event *
>> +new_event(const char *name)
>> +{
>> + struct rte_pmu_event *event;
>> +
>> + event = calloc(1, sizeof(*event));
>> + if (event == NULL)
>> + goto out;
>> +
>> + event->name = strdup(name);
>> + if (event->name == NULL) {
>> + free(event);
>> + event = NULL;
>> + }
>> +
>> +out:
>> + return event;
>> +}
>> +
>> +static void
>> +free_event(struct rte_pmu_event *event) {
>> + free(event->name);
>> + free(event);
>> +}
>> +
>> +int
>> +rte_pmu_add_event(const char *name)
>> +{
>> + struct rte_pmu_event *event;
>> + char path[PATH_MAX];
>> +
>> + if (!rte_pmu.initialized) {
>> + PMU_LOG(ERR, "PMU is not initialized");
>> + return -ENODEV;
>> + }
>> +
>> + if (rte_pmu.num_group_events + 1 >= RTE_MAX_NUM_GROUP_EVENTS) {
>> + PMU_LOG(ERR, "Excessive number of events in a group (%d > %d)",
>> + rte_pmu.num_group_events, RTE_MAX_NUM_GROUP_EVENTS);
>> + return -ENOSPC;
>> + }
>> +
>> + snprintf(path, sizeof(path), EVENT_SOURCE_DEVICES_PATH "/%s/events/%s", rte_pmu.name, name);
>> + if (access(path, R_OK)) {
>> + PMU_LOG(ERR, "Cannot access %s", path);
>> + return -ENODEV;
>> + }
>> +
>> + TAILQ_FOREACH(event, &rte_pmu.event_list, next) {
>> + if (strcmp(event->name, name))
>> + continue;
>> +
>> + return event->index;
>> + }
>> +
>> + event = new_event(name);
>> + if (event == NULL) {
>> + PMU_LOG(ERR, "Failed to create event %s", name);
>> + return -ENOMEM;
>> + }
>> +
>> + event->index = rte_pmu.num_group_events++;
>> + TAILQ_INSERT_TAIL(&rte_pmu.event_list, event, next);
>> +
>> + return event->index;
>> +}
>> +
>> +int
>> +rte_pmu_init(void)
>> +{
>> + int ret;
>> +
>> + if (rte_pmu.initialized)
>> + return 0;
>> +
>> + ret = scan_pmus();
>> + if (ret) {
>> + PMU_LOG(ERR, "Failed to scan for event sources");
>> + goto out;
>> + }
>> +
>> + ret = pmu_arch_init();
>> + if (ret) {
>> + PMU_LOG(ERR, "Failed to setup arch internals");
>> + goto out;
>> + }
>> +
>> + TAILQ_INIT(&rte_pmu.event_list);
>> + rte_pmu.initialized = 1;
>> +out:
>> + if (ret) {
>> + free(rte_pmu.name);
>> + rte_pmu.name = NULL;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +void
>> +rte_pmu_fini(void)
>> +{
>> + struct rte_pmu_event *event, *tmp_event;
>> + struct rte_pmu_event_group *group;
>> + unsigned int i;
>> +
>> + if (!rte_pmu.initialized)
>> + return;
>> +
>> + RTE_TAILQ_FOREACH_SAFE(event, &rte_pmu.event_list, next, tmp_event) {
>> + TAILQ_REMOVE(&rte_pmu.event_list, event, next);
>> + free_event(event);
>> + }
>> +
>> + for (i = 0; i < RTE_DIM(rte_pmu.event_groups); i++) {
>> + group = &rte_pmu.event_groups[i];
>> + if (!group->enabled)
>> + continue;
>> +
>> + cleanup_events(group);
>> + }
>> +
>> + pmu_arch_fini();
>> + free(rte_pmu.name);
>> + rte_pmu.name = NULL;
>> + rte_pmu.num_group_events = 0;
>> +}
>> diff --git a/lib/pmu/rte_pmu.h b/lib/pmu/rte_pmu.h new file mode
>> 100644 index 0000000000..7d10a0dc56
>> --- /dev/null
>> +++ b/lib/pmu/rte_pmu.h
>> @@ -0,0 +1,205 @@
>> +/* SPDX-License-Identifier: BSD-3-Clause
>> + * Copyright(c) 2024 Marvell
>> + */
>> +
>> +#ifndef _RTE_PMU_H_
>> +#define _RTE_PMU_H_
>> +
>> +/**
>> + * @file
>> + *
>> + * PMU event tracing operations
>> + *
>> + * This file defines generic API and types necessary to setup PMU and
>> + * read selected counters in runtime. Exported APIs are generally not MT-safe.
>> + * One exception is rte_pmu_read() which can be called concurrently
>> +once
>> + * everything has been setup.
>> + */
>> +
>
>From reading the code - I can see ithat PMU API is not MT safe.
>The only function that can run in parallel is rte_pmu_read(), correct?
>All other combinations: let say pmu_read() and add_event() are not possible, right?
>If so, then it is probably worth to articulate that explicitly in the public API comments, after
>all extra comment doesn't hurt.
>
Yes, when it comes to this version pmu_read() is the only function that can be called concurrently
on different lcores. Okay, I'll try to rewrite existing comment to make that more explicit.
>> +#ifdef __cplusplus
>> +extern "C" {
>> +#endif
>> +
>> +#include <errno.h>
>> +#include <linux/perf_event.h>
>> +
>> +#include <rte_atomic.h>
>> +#include <rte_branch_prediction.h>
>> +#include <rte_common.h>
>> +#include <rte_compat.h>
>> +#include <rte_lcore.h>
>> +
>> +/** Maximum number of events in a group */ #define
>> +RTE_MAX_NUM_GROUP_EVENTS 8
>> +
>> +/**
>> + * A structure describing a group of events.
>> + */
>> +struct __rte_cache_aligned rte_pmu_event_group {
>> + /** array of user pages */
>> + struct perf_event_mmap_page *mmap_pages[RTE_MAX_NUM_GROUP_EVENTS];
>> + int fds[RTE_MAX_NUM_GROUP_EVENTS]; /**< array of event descriptors */
>> + TAILQ_ENTRY(rte_pmu_event_group) next; /**< list entry */
>> + bool enabled; /**< true if group was enabled on particular lcore */
>> +};
>> +
>> +/**
>> + * A PMU state container.
>> + */
>> +struct rte_pmu {
>> + struct rte_pmu_event_group event_groups[RTE_MAX_LCORE]; /**< event groups */
>> + unsigned int num_group_events; /**< number of events in a group */
>> + unsigned int initialized; /**< initialization counter */
>> + char *name; /**< name of core PMU listed under /sys/bus/event_source/devices */
>> + TAILQ_HEAD(, rte_pmu_event) event_list; /**< list of matching events
>> +*/ };
>> +
>> +/** 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) ({
>> +(void)(index); 0; }) #endif
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice
>> + *
>> + * Read PMU counter.
>> + *
>> + * @warning This should not be called directly.
>> + *
>> + * @param pc
>> + * Pointer to the mmapped user page.
>> + * @return
>> + * Counter value read from hardware.
>> + */
>> +__rte_experimental
>> +static __rte_always_inline uint64_t
>> +__rte_pmu_read_userpage(struct perf_event_mmap_page *pc) { #define
>> +__RTE_PMU_READ_ONCE(x) (*(const volatile typeof(x) *)&(x))
>> + uint64_t width, offset;
>> + uint32_t seq, index;
>> + int64_t pmc;
>> +
>> + for (;;) {
>> + seq = __RTE_PMU_READ_ONCE(pc->lock);
>> + rte_compiler_barrier();
>> + index = __RTE_PMU_READ_ONCE(pc->index);
>> + offset = __RTE_PMU_READ_ONCE(pc->offset);
>> + width = __RTE_PMU_READ_ONCE(pc->pmc_width);
>> +
>> + /* index set to 0 means that particular counter cannot be used */
>> + if (likely(pc->cap_user_rdpmc && index)) {
>> + pmc = rte_pmu_pmc_read(index - 1);
>> + pmc <<= 64 - width;
>> + pmc >>= 64 - width;
>> + offset += pmc;
>> + }
>> +
>> + rte_compiler_barrier();
>> +
>> + if (likely(__RTE_PMU_READ_ONCE(pc->lock) == seq))
>> + return offset;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice
>> + *
>> + * Enable group of events on the calling lcore.
>> + *
>> + * @warning This should not be called directly.
>> + *
>> + * @param group
>> + * Pointer to the group which will be enabled.
>> + * @return
>> + * 0 in case of success, negative value otherwise.
>> + */
>> +__rte_experimental
>> +int
>> +__rte_pmu_enable_group(struct rte_pmu_event_group *group);
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice
>> + *
>> + * Initialize PMU library.
>> + *
>> + * @return
>> + * 0 in case of success, negative value otherwise.
>> + */
>> +__rte_experimental
>> +int
>> +rte_pmu_init(void);
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice
>> + *
>> + * Finalize PMU library.
>> + */
>> +__rte_experimental
>> +void
>> +rte_pmu_fini(void);
>> +
>> +/**
>> + * @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.
>> + */
>
>As I remember that function implies to be called from the thread bind to one particular cpu.
>If that is still the case - please state it explicitly in the comments above.
>
Yes, that still the case. Will mention that.
>> +__rte_experimental
>> +static __rte_always_inline uint64_t
>> +rte_pmu_read(unsigned int index)
>> +{
>> + struct rte_pmu_event_group *group =
>> +&rte_pmu.event_groups[rte_lcore_id()];
>
>I think we better check here value returned by rte_lcore_id() before using it as an index.
>
I'll add this check. Hopefully it will disappear once this gets switched to per-lcore-variables
(given performance won't deteriorate).
>> + int ret;
>> +
>> + if (unlikely(!rte_pmu.initialized))
>> + return 0;
>> +
>> + if (unlikely(!group->enabled)) {
>> + ret = __rte_pmu_enable_group(group);
>> + if (ret)
>> + return 0;
>> + }
>> +
>> + if (unlikely(index >= rte_pmu.num_group_events))
>> + return 0;
>> +
>> + return __rte_pmu_read_userpage(group->mmap_pages[index]);
>> +}
>> +
>> +#ifdef __cplusplus
>> +}
>> +#endif
>> +
>> +#endif /* _RTE_PMU_H_ */
>> diff --git a/lib/pmu/version.map b/lib/pmu/version.map new file mode
>> 100644 index 0000000000..d0f907d13d
>> --- /dev/null
>> +++ b/lib/pmu/version.map
>> @@ -0,0 +1,13 @@
>> +EXPERIMENTAL {
>> + global:
>> +
>> + # added in 24.11
>> + __rte_pmu_enable_group;
>> + rte_pmu;
>> + rte_pmu_add_event;
>> + rte_pmu_fini;
>> + rte_pmu_init;
>> + rte_pmu_read;
>> +
>> + local: *;
>> +};
>> --
>> 2.34.1
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