lttng-context-perf-counters.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-perf-counters.c
   4  *
   5  * LTTng performance monitoring counters (perf-counters) integration module.
   6  *
   7  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/slab.h>
  12 #include <linux/perf_event.h>
  13 #include <linux/list.h>
  14 #include <linux/string.h>
  15 #include <linux/cpu.h>
  16 #include <linux/mm.h>
  17 #include <lttng/lttng-events.h>
  18 #include <ringbuffer/frontend_types.h>
  19 #include <lttng/lttng-tracer.h>
  20
  21 static
  22 size_t perf_counter_get_size(size_t offset)
  23 {
  24         size_t size = 0;
  25
  26         size += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
  27         size += sizeof(uint64_t);
  28         return size;
  29 }
  30
  31 static
  32 void perf_counter_record(struct lttng_ctx_field *field,
  33                          struct lib_ring_buffer_ctx *ctx,
  34                          struct lttng_channel *chan)
  35 {
  36         struct perf_event *event;
  37         uint64_t value;
  38
  39         event = field->u.perf_counter->e[ctx->cpu];
  40         if (likely(event)) {
  41                 if (unlikely(event->state == PERF_EVENT_STATE_ERROR)) {
  42                         value = 0;
  43                 } else {
  44                         event->pmu->read(event);
  45                         value = local64_read(&event->count);
  46                 }
  47         } else {
  48                 /*
  49                  * Perf chooses not to be clever and not to support enabling a
  50                  * perf counter before the cpu is brought up. Therefore, we need
  51                  * to support having events coming (e.g. scheduler events)
  52                  * before the counter is setup. Write an arbitrary 0 in this
  53                  * case.
  54                  */
  55                 value = 0;
  56         }
  57         lib_ring_buffer_align_ctx(ctx, lttng_alignof(value));
  58         chan->ops->event_write(ctx, &value, sizeof(value));
  59 }
  60
  61 static
  62 void overflow_callback(struct perf_event *event,
  63                        struct perf_sample_data *data,
  64                        struct pt_regs *regs)
  65 {
  66 }
  67
  68 static
  69 void lttng_destroy_perf_counter_field(struct lttng_ctx_field *field)
  70 {
  71         struct perf_event **events = field->u.perf_counter->e;
  72
  73         {
  74                 int ret;
  75
  76                 ret = cpuhp_state_remove_instance(lttng_hp_online,
  77                         &field->u.perf_counter->cpuhp_online.node);
  78                 WARN_ON(ret);
  79                 ret = cpuhp_state_remove_instance(lttng_hp_prepare,
  80                         &field->u.perf_counter->cpuhp_prepare.node);
  81                 WARN_ON(ret);
  82         }
  83         kfree(field->event_field.name);
  84         kfree(field->u.perf_counter->attr);
  85         kvfree(events);
  86         kfree(field->u.perf_counter);
  87 }
  88
  89 int lttng_cpuhp_perf_counter_online(unsigned int cpu,
  90                 struct lttng_cpuhp_node *node)
  91 {
  92         struct lttng_perf_counter_field *perf_field =
  93                 container_of(node, struct lttng_perf_counter_field,
  94                                 cpuhp_online);
  95         struct perf_event **events = perf_field->e;
  96         struct perf_event_attr *attr = perf_field->attr;
  97         struct perf_event *pevent;
  98
  99         pevent = perf_event_create_kernel_counter(attr,
 100                         cpu, NULL, overflow_callback, NULL);
 101         if (!pevent || IS_ERR(pevent))
 102                 return -EINVAL;
 103         if (pevent->state == PERF_EVENT_STATE_ERROR) {
 104                 perf_event_release_kernel(pevent);
 105                 return -EINVAL;
 106         }
 107         barrier();      /* Create perf counter before setting event */
 108         events[cpu] = pevent;
 109         return 0;
 110 }
 111
 112 int lttng_cpuhp_perf_counter_dead(unsigned int cpu,
 113                 struct lttng_cpuhp_node *node)
 114 {
 115         struct lttng_perf_counter_field *perf_field =
 116                 container_of(node, struct lttng_perf_counter_field,
 117                                 cpuhp_prepare);
 118         struct perf_event **events = perf_field->e;
 119         struct perf_event *pevent;
 120
 121         pevent = events[cpu];
 122         events[cpu] = NULL;
 123         barrier();      /* NULLify event before perf counter teardown */
 124         perf_event_release_kernel(pevent);
 125         return 0;
 126 }
 127
 128 int lttng_add_perf_counter_to_ctx(uint32_t type,
 129                                   uint64_t config,
 130                                   const char *name,
 131                                   struct lttng_ctx **ctx)
 132 {
 133         struct lttng_ctx_field *field;
 134         struct lttng_perf_counter_field *perf_field;
 135         struct perf_event **events;
 136         struct perf_event_attr *attr;
 137         int ret;
 138         char *name_alloc;
 139
 140         events = kvzalloc(num_possible_cpus() * sizeof(*events), GFP_KERNEL);
 141         if (!events)
 142                 return -ENOMEM;
 143
 144         attr = kzalloc(sizeof(struct perf_event_attr), GFP_KERNEL);
 145         if (!attr) {
 146                 ret = -ENOMEM;
 147                 goto error_attr;
 148         }
 149
 150         attr->type = type;
 151         attr->config = config;
 152         attr->size = sizeof(struct perf_event_attr);
 153         attr->pinned = 1;
 154         attr->disabled = 0;
 155
 156         perf_field = kzalloc(sizeof(struct lttng_perf_counter_field), GFP_KERNEL);
 157         if (!perf_field) {
 158                 ret = -ENOMEM;
 159                 goto error_alloc_perf_field;
 160         }
 161         perf_field->e = events;
 162         perf_field->attr = attr;
 163
 164         name_alloc = kstrdup(name, GFP_KERNEL);
 165         if (!name_alloc) {
 166                 ret = -ENOMEM;
 167                 goto name_alloc_error;
 168         }
 169
 170         field = lttng_append_context(ctx);
 171         if (!field) {
 172                 ret = -ENOMEM;
 173                 goto append_context_error;
 174         }
 175         if (lttng_find_context(*ctx, name_alloc)) {
 176                 ret = -EEXIST;
 177                 goto find_error;
 178         }
 179
 180         perf_field->cpuhp_prepare.component = LTTNG_CONTEXT_PERF_COUNTERS;
 181         ret = cpuhp_state_add_instance(lttng_hp_prepare,
 182                 &perf_field->cpuhp_prepare.node);
 183         if (ret)
 184                 goto cpuhp_prepare_error;
 185
 186         perf_field->cpuhp_online.component = LTTNG_CONTEXT_PERF_COUNTERS;
 187         ret = cpuhp_state_add_instance(lttng_hp_online,
 188                 &perf_field->cpuhp_online.node);
 189         if (ret)
 190                 goto cpuhp_online_error;
 191
 192         field->destroy = lttng_destroy_perf_counter_field;
 193
 194         field->event_field.name = name_alloc;
 195         field->event_field.type.atype = atype_integer;
 196         field->event_field.type.u.integer.size = sizeof(uint64_t) * CHAR_BIT;
 197         field->event_field.type.u.integer.alignment = lttng_alignof(uint64_t) * CHAR_BIT;
 198         field->event_field.type.u.integer.signedness = lttng_is_signed_type(uint64_t);
 199         field->event_field.type.u.integer.reverse_byte_order = 0;
 200         field->event_field.type.u.integer.base = 10;
 201         field->event_field.type.u.integer.encoding = lttng_encode_none;
 202         field->get_size = perf_counter_get_size;
 203         field->record = perf_counter_record;
 204         field->u.perf_counter = perf_field;
 205         lttng_context_update(*ctx);
 206
 207         return 0;
 208
 209 cpuhp_online_error:
 210         {
 211                 int remove_ret;
 212
 213                 remove_ret = cpuhp_state_remove_instance(lttng_hp_prepare,
 214                                 &perf_field->cpuhp_prepare.node);
 215                 WARN_ON(remove_ret);
 216         }
 217 cpuhp_prepare_error:
 218 find_error:
 219         lttng_remove_context_field(ctx, field);
 220 append_context_error:
 221         kfree(name_alloc);
 222 name_alloc_error:
 223         kfree(perf_field);
 224 error_alloc_perf_field:
 225         kfree(attr);
 226 error_attr:
 227         kvfree(events);
 228         return ret;
 229 }