[RFC PATCH v2 08/20] tracing/filters: Further optimise scalar vs cpumask comparison

Valentin Schneider
2023-07-20T16:34:24Z

Per the previous commits, we now only enter do_filter_scalar_cpumask() with
a mask of weight greater than one. Optimise the equality checks.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
kernel/trace/trace_events_filter.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index fd72dacc5d1b8..3a529214a21b7 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -667,6 +667,25 @@ do_filter_cpumask(int op, const struct cpumask *mask, const struct cpumask *cmp)
/* Optimisation of do_filter_cpumask() for scalar fields */
static inline int
do_filter_scalar_cpumask(int op, unsigned int cpu, const struct cpumask *mask)
+{
+ /*
+ * Per the weight-of-one cpumask optimisations, the mask passed in this
+ * function has a weight >= 2, so it is never equal to a single scalar.
+ */
+ switch (op) {
+ case OP_EQ:
+ return false;
+ case OP_NE:
+ return true;
+ case OP_BAND:
+ return cpumask_test_cpu(cpu, mask);
+ default:
+ return 0;
+ }
+}
+
+static inline int
+do_filter_cpumask_scalar(int op, const struct cpumask *mask, unsigned int cpu)
{
switch (op) {
case OP_EQ:
@@ -966,12 +985,7 @@ static int filter_pred_cpumask_cpu(struct filter_pred *pred, void *event)
const struct cpumask *mask = (event + loc);
unsigned int cpu = pred->val;

- /*
- * This inverts the usual usage of the function (field is first element,
- * user parameter is second), but that's fine because the (scalar, mask)
- * operations used are symmetric.
- */
- return do_filter_scalar_cpumask(pred->op, cpu, mask);
+ return do_filter_cpumask_scalar(pred->op, mask, cpu);
}

/* Filter predicate for COMM. */
--
2.31.1