> From: Tomasz Duszynski [mailto:tduszyn...@marvell.com]
> Sent: Tuesday, 13 December 2022 11.44
>
> 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 <tduszyn...@marvell.com>
> ---
> +++ 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);
> + 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)
> +{
> + struct rte_pmu_event_group *group = &rte_pmu->group[lcore_id];
> + int i;
> +
> + if (!group->fds)
> + return;
> +
> + 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)
> +{
> + 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);
> +
> + 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 */
There seems to be a lot of indirection involved here. Why are these arrays not
statically sized, instead of dynamically allocated?
Also, what is the reason for hiding the type struct perf_event_mmap_page
**mmap_pages opaque by using void **mmap_pages instead?
> + 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;
Again, why not just extern struct rte_pmu, instead of dynamic allocation?
> +
> +/** 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;
> + }
Why is the group not enabled in the setup function, rte_pmu_add_event(),
instead of here, in the hot path?
> +
> + 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]);
Using fixed size arrays instead of multiple indirections via pointers is
faster. It could be:
return rte_pmu_read_userpage((struct perf_event_mmap_page
*)rte_pmu.group[lcore_id].mmap_pages[index]);
With our without suggested performance improvements...
Series-acked-by: Morten Brørup <m...@smartsharesystems.com>
