mirror of
https://github.com/varun-r-mallya/sysprof.git
synced 2025-12-31 20:36:25 +00:00
libsysprof-profile: backoff perf GSource when possible
We have a fairly large buffer for perf events, so we should be able to process these much less frequently to help reduce the process performing the profile from showing up in the profiling results.
This commit is contained in:
Christian Hergert
@ -70,6 +70,7 @@ struct _SysprofPerfEventStream
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struct perf_event_attr attr;
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int self_pid;
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int cpu;
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int group_fd;
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gulong flags;
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@ -81,7 +82,6 @@ struct _SysprofPerfEventStream
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DexPromise *promise;
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int perf_fd;
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gpointer perf_fd_tag;
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struct perf_event_mmap_page *map;
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guint8 *map_data;
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@ -94,6 +94,7 @@ typedef struct _SysprofPerfEventSource
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{
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GSource source;
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SysprofPerfEventStream *stream;
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gint64 next_ready_time;
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int timeout_msec;
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} SysprofPerfEventSource;
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@ -148,10 +149,14 @@ build_options_dict (const struct perf_event_attr *attr)
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static void
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sysprof_perf_event_stream_flush (SysprofPerfEventStream *self)
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{
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SysprofPerfEventSource *source = (SysprofPerfEventSource *)self->source;
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guint64 n_bytes = N_PAGES * sysprof_getpagesize ();
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guint64 mask = n_bytes - 1;
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guint64 head;
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guint64 tail;
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gboolean lost_records = FALSE;
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guint us = 0;
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guint them = 0;
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g_assert (SYSPROF_IS_PERF_EVENT_STREAM (self));
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@ -170,8 +175,10 @@ sysprof_perf_event_stream_flush (SysprofPerfEventStream *self)
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while ((head - tail) >= sizeof (struct perf_event_header))
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{
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g_autofree guint8 *free_me = NULL;
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const SysprofPerfEvent *event;
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struct perf_event_header *header;
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guint8 buffer[4096];
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gboolean is_self = FALSE;
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/* Note that:
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*
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@ -213,9 +220,38 @@ sysprof_perf_event_stream_flush (SysprofPerfEventStream *self)
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header = (struct perf_event_header *)(gpointer)b;
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}
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if (self->callback != NULL)
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self->callback ((SysprofPerfEvent *)header, self->cpu, self->callback_data);
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event = (SysprofPerfEvent *)header;
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switch (event->header.type)
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{
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default:
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case PERF_RECORD_COMM:
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case PERF_RECORD_EXIT:
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case PERF_RECORD_FORK:
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break;
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case PERF_RECORD_SAMPLE:
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is_self = event->callchain.pid == self->self_pid;
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break;
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case PERF_RECORD_READ:
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case PERF_RECORD_THROTTLE:
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case PERF_RECORD_UNTHROTTLE:
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goto skip_callback;
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case PERF_RECORD_LOST:
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lost_records = TRUE;
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g_debug ("Lost records from perf");
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break;
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}
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if (self->callback != NULL)
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self->callback (event, self->cpu, self->callback_data);
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us += is_self;
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them += !is_self;
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skip_callback:
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tail += header->size;
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}
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@ -228,62 +264,56 @@ sysprof_perf_event_stream_flush (SysprofPerfEventStream *self)
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#endif
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self->map->data_tail = tail;
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/* If we lost records them we took too long to process events and
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* need to speed up how often we process incoming records. However,
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* if we are the cause of that (due to running to frequently), then
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* we need to back-off.
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*/
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if (lost_records && us < them/3)
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{
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if (source->timeout_msec > 1)
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source->timeout_msec -= 5;
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}
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else
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{
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if (source->timeout_msec < 500)
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{
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if (us < 5 && them < 5)
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source->timeout_msec += 100;
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else
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source->timeout_msec += 10;
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}
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}
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}
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static gboolean
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sysprof_perf_event_source_prepare (GSource *gsource,
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int *timeout)
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{
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SysprofPerfEventSource *source = (SysprofPerfEventSource *)gsource;
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SysprofPerfEventStream *self = source->stream;
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if (timeout != NULL)
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*timeout = source->timeout_msec;
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return self != NULL &&
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self->active &&
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self->map != NULL &&
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self->tail != self->map->data_head;
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}
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static gboolean
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sysprof_perf_event_source_check (GSource *gsource)
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{
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SysprofPerfEventSource *source = (SysprofPerfEventSource *)gsource;
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SysprofPerfEventStream *self = source->stream;
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return self != NULL &&
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self->active &&
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self->map != NULL &&
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self->tail != self->map->data_head;
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}
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static gboolean
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sysprof_perf_event_source_dispatch (GSource *source,
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sysprof_perf_event_source_dispatch (GSource *gsource,
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GSourceFunc callback,
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gpointer user_data)
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{
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return callback ? callback (user_data) : G_SOURCE_CONTINUE;
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}
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SysprofPerfEventSource *source = (SysprofPerfEventSource *)gsource;
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SysprofPerfEventStream *self = source->stream;
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static GSourceFuncs source_funcs = {
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.prepare = sysprof_perf_event_source_prepare,
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.check = sysprof_perf_event_source_check,
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.dispatch = sysprof_perf_event_source_dispatch,
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};
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if (source->next_ready_time <= g_source_get_time (gsource) &&
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self != NULL &&
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self->active &&
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self->map != NULL &&
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self->tail != self->map->data_head)
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sysprof_perf_event_stream_flush (self);
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else
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source->timeout_msec = MIN (500, source->timeout_msec + 50);
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static gboolean
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sysprof_perf_event_stream_dispatch (gpointer user_data)
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{
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SysprofPerfEventStream *self = user_data;
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g_assert (SYSPROF_IS_PERF_EVENT_STREAM (self));
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sysprof_perf_event_stream_flush (self);
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source->next_ready_time = g_get_monotonic_time () + (source->timeout_msec * 1000);
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g_source_set_ready_time (self->source, source->next_ready_time);
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return G_SOURCE_CONTINUE;
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}
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static GSourceFuncs source_funcs = {
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.dispatch = sysprof_perf_event_source_dispatch,
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};
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static void
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sysprof_perf_event_stream_finalize (GObject *object)
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{
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@ -353,6 +383,7 @@ static void
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sysprof_perf_event_stream_init (SysprofPerfEventStream *self)
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{
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self->perf_fd = -1;
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self->self_pid = getpid ();
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}
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static void
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@ -383,7 +414,6 @@ sysprof_perf_event_stream_new_cb (GObject *object,
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guint8 *map;
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self->perf_fd = fd;
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self->perf_fd_tag = g_source_add_unix_fd (self->source, fd, G_IO_ERR);
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map_size = N_PAGES * sysprof_getpagesize () + sysprof_getpagesize ();
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map = mmap (NULL, map_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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@ -428,6 +458,7 @@ sysprof_perf_event_stream_new (GDBusConnection *connection,
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g_autoptr(GUnixFDList) fd_list = NULL;
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g_autoptr(DexPromise) promise = NULL;
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g_autoptr(GVariant) options = NULL;
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g_autofree char *name = NULL;
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int group_fd_handle = -1;
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g_return_val_if_fail (G_IS_DBUS_CONNECTION (connection), NULL);
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@ -452,10 +483,13 @@ sysprof_perf_event_stream_new (GDBusConnection *connection,
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g_source_new (&source_funcs, sizeof (SysprofPerfEventSource));
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source->stream = self;
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source->timeout_msec = 5;
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source->next_ready_time = g_get_monotonic_time () + (source->timeout_msec * 1000);
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self->source = (GSource *)source;
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g_source_set_callback (self->source, sysprof_perf_event_stream_dispatch, self, NULL);
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g_source_set_name (self->source, "[perf]");
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name = g_strdup_printf ("[perf cpu%d]", cpu);
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g_source_set_ready_time (self->source, source->next_ready_time);
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g_source_set_name (self->source, name);
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g_source_attach (self->source, NULL);
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fd_list = g_unix_fd_list_new ();
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@ -508,8 +542,6 @@ sysprof_perf_event_stream_enable (SysprofPerfEventStream *self,
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self->active = TRUE;
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g_source_modify_unix_fd (self->source, self->perf_fd_tag, G_IO_IN);
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g_object_notify_by_pspec (G_OBJECT (self), properties [PROP_ACTIVE]);
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return TRUE;
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@ -536,8 +568,6 @@ sysprof_perf_event_stream_disable (SysprofPerfEventStream *self,
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self->active = FALSE;
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g_source_modify_unix_fd (self->source, self->perf_fd_tag, G_IO_ERR);
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g_object_notify_by_pspec (G_OBJECT (self), properties [PROP_ACTIVE]);
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return TRUE;
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