linux-kernel - [PATCH v6 1/5] tracing: Allow multiple hitcount values in histograms

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Message-Id: <166610812248.56030.16754785928712505251.stgit@devnote2>
Date:   Wed, 19 Oct 2022 00:48:42 +0900
From:   "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Tom Zanussi <zanussi@...nel.org>,
        linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v6 1/5] tracing: Allow multiple hitcount values in histograms

From: Tom Zanussi <zanussi@...nel.org>

The hitcount is treated specially in the histograms - since it's
always expected to be there regardless of whether the user specified
anything or not, it's always added as the first histogram value.

Currently the code doesn't allow it to be added more than once as a
value, which is inconsistent with all the other possible values.  It
would seem to be a pointless thing to want to do, but other features
being added such as percent and graph modifiers don't work properly
with the current hitcount restrictions.

Fix this by allowing multiple hitcounts to be added.

Signed-off-by: Tom Zanussi <zanussi@...nel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Tested-by: Tom Zanussi <zanussi@...nel.org>
---
 kernel/trace/trace_events_hist.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 48465f7e97b4..13bb7ec45836 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1356,6 +1356,8 @@ static const char *hist_field_name(struct hist_field *field,
 			field_name = field->name;
 	} else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
 		field_name = "common_timestamp";
+	else if (field->flags & HIST_FIELD_FL_HITCOUNT)
+		field_name = "hitcount";
 
 	if (field_name == NULL)
 		field_name = "";
@@ -2328,6 +2330,8 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
 			hist_data->attrs->ts_in_usecs = true;
 	} else if (strcmp(field_name, "common_cpu") == 0)
 		*flags |= HIST_FIELD_FL_CPU;
+	else if (strcmp(field_name, "hitcount") == 0)
+		*flags |= HIST_FIELD_FL_HITCOUNT;
 	else {
 		field = trace_find_event_field(file->event_call, field_name);
 		if (!field || !field->size) {
@@ -4328,8 +4332,8 @@ static int create_var_field(struct hist_trigger_data *hist_data,
 static int create_val_fields(struct hist_trigger_data *hist_data,
 			     struct trace_event_file *file)
 {
+	unsigned int i, j = 1, n_hitcount = 0;
 	char *fields_str, *field_str;
-	unsigned int i, j = 1;
 	int ret;
 
 	ret = create_hitcount_val(hist_data);
@@ -4346,8 +4350,10 @@ static int create_val_fields(struct hist_trigger_data *hist_data,
 		if (!field_str)
 			break;
 
-		if (strcmp(field_str, "hitcount") == 0)
-			continue;
+		if (strcmp(field_str, "hitcount") == 0) {
+			if (!n_hitcount++)
+				continue;
+		}
 
 		ret = create_val_field(hist_data, j++, file, field_str);
 		if (ret)