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

Valentin Schneider
2023-07-20T16:34:14Z

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(-)

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);
--
2.31.1