[RFC PATCH v2 03/20] tracing/filters: Enable filtering a scalar field by a cpumask

Valentin Schneider
2023-07-20T16:33:45Z

Several events use a scalar field to denote a CPU:
o sched_wakeup.target_cpu
o sched_migrate_task.orig_cpu,dest_cpu
o sched_move_numa.src_cpu,dst_cpu
o ipi_send_cpu.cpu
o ...

Filtering these currently requires using arithmetic comparison functions,
which can be tedious when dealing with interleaved SMT or NUMA CPU ids.

Allow these to be filtered by a user-provided cpumask, which enables e.g.:

$ trace-cmd record -e 'sched_wakeup' -f 'target_cpu & CPUS{2,4,6,8-32}'

Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
NOTE: I went with an implicit cpumask conversion of the event field, as
AFAICT predicate_parse() does not support parsing the application of a
function to a field (e.g. 'CPUS(target_cpu) & CPUS{2,4,6,8-32}')
---
kernel/trace/trace_events_filter.c | 92 ++++++++++++++++++++++++++----
1 file changed, 81 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index cb1863dfa280b..1e14f801685a8 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -46,15 +46,19 @@ static const char * ops[] = { OPS };
enum filter_pred_fn {
FILTER_PRED_FN_NOP,
FILTER_PRED_FN_64,
+ FILTER_PRED_FN_64_CPUMASK,
FILTER_PRED_FN_S64,
FILTER_PRED_FN_U64,
FILTER_PRED_FN_32,
+ FILTER_PRED_FN_32_CPUMASK,
FILTER_PRED_FN_S32,
FILTER_PRED_FN_U32,
FILTER_PRED_FN_16,
+ FILTER_PRED_FN_16_CPUMASK,
FILTER_PRED_FN_S16,
FILTER_PRED_FN_U16,
FILTER_PRED_FN_8,
+ FILTER_PRED_FN_8_CPUMASK,
FILTER_PRED_FN_S8,
FILTER_PRED_FN_U8,
FILTER_PRED_FN_COMM,
@@ -643,6 +647,39 @@ predicate_parse(const char *str, int nr_parens, int nr_preds,
return ERR_PTR(ret);
}

+static inline int
+do_filter_cpumask(int op, const struct cpumask *mask, const struct cpumask *cmp)
+{
+ switch (op) {
+ case OP_EQ:
+ return cpumask_equal(mask, cmp);
+ case OP_NE:
+ return !cpumask_equal(mask, cmp);
+ case OP_BAND:
+ return cpumask_intersects(mask, cmp);
+ default:
+ return 0;
+ }
+}
+
+/* Optimisation of do_filter_cpumask() for scalar fields */
+static inline int
+do_filter_scalar_cpumask(int op, unsigned int cpu, const struct cpumask *mask)
+{
+ switch (op) {
+ case OP_EQ:
+ return cpumask_test_cpu(cpu, mask) &&
+ cpumask_nth(1, mask) >= nr_cpu_ids;
+ case OP_NE:
+ return !cpumask_test_cpu(cpu, mask) ||
+ cpumask_nth(1, mask) < nr_cpu_ids;
+ case OP_BAND:
+ return cpumask_test_cpu(cpu, mask);
+ default:
+ return 0;
+ }
+}
+
enum pred_cmp_types {
PRED_CMP_TYPE_NOP,
PRED_CMP_TYPE_LT,
@@ -686,6 +723,18 @@ static int filter_pred_##type(struct filter_pred *pred, void *event) \
} \
}

+#define DEFINE_CPUMASK_COMPARISON_PRED(size) \
+static int filter_pred_##size##_cpumask(struct filter_pred *pred, void *event) \
+{ \
+ u##size *addr = (u##size *)(event + pred->offset); \
+ unsigned int cpu = *addr; \
+ \
+ if (cpu >= nr_cpu_ids) \
+ return 0; \
+ \
+ return do_filter_scalar_cpumask(pred->op, cpu, pred->mask); \
+}
+
#define DEFINE_EQUALITY_PRED(size) \
static int filter_pred_##size(struct filter_pred *pred, void *event) \
{ \
@@ -707,6 +756,11 @@ DEFINE_COMPARISON_PRED(u16);
DEFINE_COMPARISON_PRED(s8);
DEFINE_COMPARISON_PRED(u8);

+DEFINE_CPUMASK_COMPARISON_PRED(64);
+DEFINE_CPUMASK_COMPARISON_PRED(32);
+DEFINE_CPUMASK_COMPARISON_PRED(16);
+DEFINE_CPUMASK_COMPARISON_PRED(8);
+
DEFINE_EQUALITY_PRED(64);
DEFINE_EQUALITY_PRED(32);
DEFINE_EQUALITY_PRED(16);
@@ -891,16 +945,7 @@ static int filter_pred_cpumask(struct filter_pred *pred, void *event)
const struct cpumask *mask = (event + loc);
const struct cpumask *cmp = pred->mask;

- switch (pred->op) {
- case OP_EQ:
- return cpumask_equal(mask, cmp);
- case OP_NE:
- return !cpumask_equal(mask, cmp);
- case OP_BAND:
- return cpumask_intersects(mask, cmp);
- default:
- return 0;
- }
+ return do_filter_cpumask(pred->op, mask, cmp);
}

/* Filter predicate for COMM. */
@@ -1351,24 +1396,32 @@ static int filter_pred_fn_call(struct filter_pred *pred, void *event)
switch (pred->fn_num) {
case FILTER_PRED_FN_64:
return filter_pred_64(pred, event);
+ case FILTER_PRED_FN_64_CPUMASK:
+ return filter_pred_64_cpumask(pred, event);
case FILTER_PRED_FN_S64:
return filter_pred_s64(pred, event);
case FILTER_PRED_FN_U64:
return filter_pred_u64(pred, event);
case FILTER_PRED_FN_32:
return filter_pred_32(pred, event);
+ case FILTER_PRED_FN_32_CPUMASK:
+ return filter_pred_32_cpumask(pred, event);
case FILTER_PRED_FN_S32:
return filter_pred_s32(pred, event);
case FILTER_PRED_FN_U32:
return filter_pred_u32(pred, event);
case FILTER_PRED_FN_16:
return filter_pred_16(pred, event);
+ case FILTER_PRED_FN_16_CPUMASK:
+ return filter_pred_16_cpumask(pred, event);
case FILTER_PRED_FN_S16:
return filter_pred_s16(pred, event);
case FILTER_PRED_FN_U16:
return filter_pred_u16(pred, event);
case FILTER_PRED_FN_8:
return filter_pred_8(pred, event);
+ case FILTER_PRED_FN_8_CPUMASK:
+ return filter_pred_8_cpumask(pred, event);
case FILTER_PRED_FN_S8:
return filter_pred_s8(pred, event);
case FILTER_PRED_FN_U8:
@@ -1606,6 +1659,7 @@ static int parse_pred(const char *str, void *data,

switch (field->filter_type) {
case FILTER_CPUMASK:
+ case FILTER_OTHER:
break;
default:
parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i);
@@ -1658,8 +1712,24 @@ static int parse_pred(const char *str, void *data,

/* Move along */
i++;
- if (field->filter_type == FILTER_CPUMASK)
+ if (field->filter_type == FILTER_CPUMASK) {
pred->fn_num = FILTER_PRED_FN_CPUMASK;
+ } else {
+ switch (field->size) {
+ case 8:
+ pred->fn_num = FILTER_PRED_FN_64_CPUMASK;
+ break;
+ case 4:
+ pred->fn_num = FILTER_PRED_FN_32_CPUMASK;
+ break;
+ case 2:
+ pred->fn_num = FILTER_PRED_FN_16_CPUMASK;
+ break;
+ case 1:
+ pred->fn_num = FILTER_PRED_FN_8_CPUMASK;
+ break;
+ }
+ }

/* This is either a string, or an integer */
} else if (str[i] == '\'' || str[i] == '"') {
--
2.31.1