[PATCH v4 03/10] tracing/boot: Support multiple handlers for per-event histogram

Masami Hiramatsu
2021-08-10T02:07:44Z

Support multiple handlers for per-event histogram in boot-time tracing.
Since the histogram can register multiple same handler-actions with
different parameters, this expands the syntax to support such cases.

With this update, the 'onmax', 'onchange' and 'onmatch' handler subkeys
under per-event histogram option will take a number subkeys optionally
as below. (see [.N])

ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist {
onmax|onchange[.N] { var = <VAR>; <ACTION> [= <PARAM>] }
onmatch[.N] { event = <EVENT>; <ACTION> [= <PARAM>] }
}

The 'N' must be a digit (or digit started word).

Thus user can add several handler-actions to the histogram,
for example,

ftrace.event.SOMEGROUP.SOMEEVENT.hist {
keys = SOME_ID; lat = common_timestamp.usecs-$ts0
onmatch.1 {
event = GROUP1.STARTEVENT1
trace = latency_event, SOME_ID, $lat
}
onmatch.2 {
event = GROUP2.STARTEVENT2
trace = latency_event, SOME_ID, $lat
}
}

Then, it can trace the elapsed time from GROUP1.STARTEVENT1 to
SOMEGROUP.SOMEEVENT, and from GROUP2.STARTEVENT2 to
SOMEGROUP.SOMEEVENT with SOME_ID key.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
kernel/trace/trace_boot.c | 43 +++++++++++++++++++++++++++++++++++--------
1 file changed, 35 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 3d0e51368f51..f024f27b3602 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -245,8 +245,9 @@ trace_boot_hist_add_array(struct xbc_node *hnode, char **bufp,
}

static int __init
-trace_boot_hist_add_handler(struct xbc_node *hnode, char **bufp,
- char *end, const char *param)
+trace_boot_hist_add_one_handler(struct xbc_node *hnode, char **bufp,
+ char *end, const char *handler,
+ const char *param)
{
struct xbc_node *knode, *anode;
const char *p;
@@ -259,7 +260,7 @@ trace_boot_hist_add_handler(struct xbc_node *hnode, char **bufp,
xbc_node_get_data(hnode), param);
return -EINVAL;
}
- append_printf(bufp, end, ":%s(%s)", xbc_node_get_data(hnode), p);
+ append_printf(bufp, end, ":%s(%s)", handler, p);

/* Compose 'action' parameter */
knode = xbc_node_find_child(hnode, "trace");
@@ -294,6 +295,32 @@ trace_boot_hist_add_handler(struct xbc_node *hnode, char **bufp,
return 0;
}

+static int __init
+trace_boot_hist_add_handlers(struct xbc_node *hnode, char **bufp,
+ char *end, const char *param)
+{
+ struct xbc_node *node;
+ const char *p, *handler;
+ int ret;
+
+ handler = xbc_node_get_data(hnode);
+
+ 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. */
+ ret = trace_boot_hist_add_one_handler(node, bufp, end, handler, param);
+ if (ret < 0)
+ break;
+ }
+
+ if (xbc_node_find_child(hnode, param))
+ ret = trace_boot_hist_add_one_handler(hnode, bufp, end, handler, param);
+
+ return ret;
+}
+
/*
* Histogram boottime tracing syntax.
*
@@ -305,8 +332,8 @@ trace_boot_hist_add_handler(struct xbc_node *hnode, char **bufp,
* name = <HISTNAME>
* var { <VAR> = <EXPR> ... }
* pause|continue|clear
- * onmax|onchange { var = <VAR>; <ACTION> [= <PARAM>] }
- * onmatch { event = <EVENT>; <ACTION> [= <PARAM>] }
+ * onmax|onchange[.N] { var = <VAR>; <ACTION> [= <PARAM>] }
+ * onmatch[.N] { event = <EVENT>; <ACTION> [= <PARAM>] }
* filter = <FILTER>
* }
*
@@ -368,13 +395,13 @@ trace_boot_compose_hist_cmd(struct xbc_node *hnode, char *buf, size_t size)

/* Histogram handler and actions */
node = xbc_node_find_child(hnode, "onmax");
- if (node && trace_boot_hist_add_handler(node, &buf, end, "var") < 0)
+ if (node && trace_boot_hist_add_handlers(node, &buf, end, "var") < 0)
return -EINVAL;
node = xbc_node_find_child(hnode, "onchange");
- if (node && trace_boot_hist_add_handler(node, &buf, end, "var") < 0)
+ if (node && trace_boot_hist_add_handlers(node, &buf, end, "var") < 0)
return -EINVAL;
node = xbc_node_find_child(hnode, "onmatch");
- if (node && trace_boot_hist_add_handler(node, &buf, end, "event") < 0)
+ if (node && trace_boot_hist_add_handlers(node, &buf, end, "event") < 0)
return -EINVAL;

p = xbc_node_find_value(hnode, "filter", NULL);