linux-kernel - [for-next][PATCH 06/14] tracing/filters: Optimise scalar vs cpumask filtering when the user mask is a single CPU

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Date:   Wed, 23 Aug 2023 22:18:18 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Leonardo Bras <leobras@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Valentin Schneider <vschneid@...hat.com>
Subject: [for-next][PATCH 06/14] tracing/filters: Optimise scalar vs cpumask filtering when the user
 mask is a single CPU

From: Valentin Schneider <vschneid@...hat.com>

Steven noted that when the user-provided cpumask contains a single CPU,
then the filtering function can use a scalar as input instead of a
full-fledged cpumask.

When the mask contains a single CPU, directly re-use the unsigned field
predicate functions. Transform '&' into '==' beforehand.

Link: https://lkml.kernel.org/r/20230707172155.70873-7-vschneid@redhat.com

Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Jonathan Corbet <corbet@....net>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Leonardo Bras <leobras@...hat.com>
Cc: Frederic Weisbecker <frederic@...nel.org>
Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Valentin Schneider <vschneid@...hat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_events_filter.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 2fe65ddeb34e..54d642fabb7f 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1750,7 +1750,7 @@ static int parse_pred(const char *str, void *data,
 		 * then we can treat it as a scalar input.
 		 */
 		single = cpumask_weight(pred->mask) == 1;
-		if (single && field->filter_type == FILTER_CPUMASK) {
+		if (single && field->filter_type != FILTER_CPU) {
 			pred->val = cpumask_first(pred->mask);
 			kfree(pred->mask);
 		}
@@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data,
 				FILTER_PRED_FN_CPUMASK;
 		} else if (field->filter_type == FILTER_CPU) {
 			pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK;
+		} else if (single) {
+			pred->op = pred->op == OP_BAND ? OP_EQ : pred->op;
+			pred->fn_num = select_comparison_fn(pred->op, field->size, false);
+			if (pred->op == OP_NE)
+				pred->not = 1;
 		} else {
 			switch (field->size) {
 			case 8:
-- 
2.40.1