From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
When tracefs_local_events() (which also uses tracefs_local_events_system())
is called, it does not set the CPU count for the tep handler. It should do
so, so make that happen.
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
Changes since v1: https://lore.kernel.org/all/20220723102232.1ba19aa6@xxxxxxxxxxxxxxxxxxxx/
- Add a comment explaining why I did the counting the way I did.
src/tracefs-events.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/src/tracefs-events.c b/src/tracefs-events.c
index 86395101c96a..b6ab8da3c8ce 100644
--- a/src/tracefs-events.c
+++ b/src/tracefs-events.c
@@ -945,6 +945,40 @@ out:
return ret;
}
+static void set_tep_cpus(const char *tracing_dir, struct tep_handle *tep)
+{
+ struct stat st;
+ char path[PATH_MAX];
+ int cpus = sysconf(_SC_NPROCESSORS_CONF);
+ int max_cpu = 0;
+ int ret;
+ int i;
+
+ if (!tracing_dir)
+ tracing_dir = tracefs_tracing_dir();
+
+ /*
+ * Paranoid: in case sysconf() above does not work.
+ * And we also only care about the number of tracing
+ * buffers that exist. If cpus is 32, but the top half
+ * is offline, there may only be 16 tracing buffers.
+ * That's what we want to know.
+ */
+ for (i = 0; !cpus || i < cpus; i++) {
+ snprintf(path, PATH_MAX, "%s/per_cpu/cpu%d", tracing_dir, i);
+ ret = stat(path, &st);
+ if (!ret && S_ISDIR(st.st_mode))
+ max_cpu = i + 1;
+ else if (i >= cpus)
+ break;
+ }
+
+ if (!max_cpu)
+ max_cpu = cpus;
+
+ tep_set_cpus(tep, max_cpu);
+}
+
/**
* tracefs_local_events_system - create a tep from the events of the specified subsystem.
*
@@ -969,6 +1003,8 @@ struct tep_handle *tracefs_local_events_system(const char *tracing_dir,
tep = NULL;
}
+ set_tep_cpus(tracing_dir, tep);
+
/* Set the long size for this tep handle */
tep_set_long_size(tep, tep_get_header_page_size(tep));
--
2.35.1
|