[PATCH v4 04/10] tracing/boot: Support multiple histograms for each event

Masami Hiramatsu
2021-08-10T02:07:50Z

Add multiple histograms support for each event. This allows
user to set multiple histograms to an event.

ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist[.N] {
...
}

The 'N' is a digit started string and it can be omitted
for the default histogram.

For example, multiple hist triggers example in the
Documentation/trace/histogram.rst can be written as below;

ftrace.event.net.netif_receive_skb.hist {
1 {
keys = skbaddr.hex
values = len
filter = len < 0
}
2 {
keys = skbaddr.hex
values = len
filter = len > 4096
}
3 {
keys = skbaddr.hex
values = len
filter = len == 256
}
4 {
keys = skbaddr.hex
values = len
}
5 {
keys = len
values = common_preempt_count
}
}

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
Changes in v3:
- Fixes a build error when CONFIG_HIST_TRIGGERS=n.
---
kernel/trace/trace_boot.c | 41 ++++++++++++++++++++++++++++++++---------
1 file changed, 32 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index f024f27b3602..1a2b270e9cda 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -324,7 +324,7 @@ trace_boot_hist_add_handlers(struct xbc_node *hnode, char **bufp,
/*
* Histogram boottime tracing syntax.
*
- * ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist {
+ * ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist[.N] {
* keys = <KEY>[,...]
* values = <VAL>[,...]
* sort = <SORT-KEY>[,...]
@@ -415,11 +415,37 @@ trace_boot_compose_hist_cmd(struct xbc_node *hnode, char *buf, size_t size)

return 0;
}
+
+static void __init
+trace_boot_init_histograms(struct trace_event_file *file,
+ struct xbc_node *hnode, char *buf, size_t size)
+{
+ struct xbc_node *node;
+ const char *p;
+
+ xbc_node_for_each_subkey(hnode, node) {
+ p = xbc_node_get_data(node);
+ if (!isdigit(p[0]))
+ continue;
+ /* All digit started node should be instances. */
+ if (trace_boot_compose_hist_cmd(node, buf, size) == 0) {
+ if (trigger_process_regex(file, buf) < 0)
+ pr_err("Failed to apply hist trigger: %s\n", buf);
+ }
+ }
+
+ if (xbc_node_find_child(hnode, "keys")) {
+ if (trace_boot_compose_hist_cmd(hnode, buf, size) == 0)
+ if (trigger_process_regex(file, buf) < 0)
+ pr_err("Failed to apply hist trigger: %s\n", buf);
+ }
+}
#else
-static int __init
-trace_boot_compose_hist_cmd(struct xbc_node *hnode, char *buf, size_t size)
+static void __init
+trace_boot_init_histograms(struct trace_event_file *file,
+ struct xbc_node *hnode, char *buf, size_t size)
{
- return -EOPNOTSUPP;
+ /* do nothing */
}
#endif

@@ -465,11 +491,8 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
pr_err("Failed to apply an action: %s\n", buf);
}
anode = xbc_node_find_child(enode, "hist");
- if (anode &&
- trace_boot_compose_hist_cmd(anode, buf, ARRAY_SIZE(buf)) == 0) {
- if (trigger_process_regex(file, buf) < 0)
- pr_err("Failed to apply hist trigger: %s\n", buf);
- }
+ if (anode)
+ trace_boot_init_histograms(file, anode, buf, ARRAY_SIZE(buf));
} else if (xbc_node_find_value(enode, "actions", NULL))
pr_err("Failed to apply event actions because CONFIG_HIST_TRIGGERS is not set.\n");