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[RFC,v2,07/20] tracing/filters: Optimise CPU vs cpumask filtering when the user mask is a single CPU

Message ID 20230720163056.2564824-8-vschneid@redhat.com (mailing list archive)
State Accepted
Commit 1cffbe6c62f10e200813ef19caea49bbde71d474
Headers show
Series context_tracking,x86: Defer some IPIs until a user->kernel transition | expand

Commit Message

Valentin Schneider July 20, 2023, 4:30 p.m. UTC 
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.

In this case we can directly re-use filter_pred_cpu(), we just need to
transform '&' into '==' before executing it.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
 kernel/trace/trace_events_filter.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
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Patch

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 54d642fabb7f1..fd72dacc5d1b8 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_CPU) {
+		if (single) {
 			pred->val = cpumask_first(pred->mask);
 			kfree(pred->mask);
 		}
@@ -1760,7 +1760,12 @@  static int parse_pred(const char *str, void *data,
 				FILTER_PRED_FN_CPUMASK_CPU :
 				FILTER_PRED_FN_CPUMASK;
 		} else if (field->filter_type == FILTER_CPU) {
-			pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK;
+			if (single) {
+				pred->op = pred->op == OP_BAND ? OP_EQ : pred->op;
+				pred->fn_num = FILTER_PRED_FN_CPU;
+			} else {
+				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);