[PATCH v3 3/6] rtla/osnoise: Leverage IPI event filters when tracing a subset of CPUs
From: Valentin Schneider <vschneid@redhat.com>
Date: 2026-07-15 15:46:53
Also in:
lkml
Subsystem:
real-time linux analysis (rtla) tools, the rest · Maintainers:
Steven Rostedt, Tomas Glozar, Linus Torvalds
Leverage the kernel event filtering infrastructure to only emit IPI events if they target CPUs that are being traced, as specified by the -c cmdline option. Note that some post-processing is still required for the ipi_send_cpumask event, as the event being emitted means *some* CPUs targeted by that event are monitored, but not all of them - userspace has to recompute that intersection. Signed-off-by: Valentin Schneider <vschneid@redhat.com> --- tools/tracing/rtla/src/osnoise_top.c | 38 ++++++++++++++++++++++++---- 1 file changed, 33 insertions(+), 5 deletions(-)
diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
index 7b5ae5336cf08..353b435fefcf8 100644
--- a/tools/tracing/rtla/src/osnoise_top.c
+++ b/tools/tracing/rtla/src/osnoise_top.c@@ -302,17 +302,13 @@ osnoise_ipi_cpu_handler(struct trace_seq *s, struct tep_record *record, struct tep_event *event, void *context) { struct osnoise_tool *tool; - struct osnoise_params *params; unsigned long long dst_cpu; struct trace_instance *trace = context; tool = container_of(trace, struct osnoise_tool, trace); - params = to_osnoise_params(tool->params); - tep_get_field_val(s, event, "cpu", record, &dst_cpu, 1); - if (CPU_ISSET(dst_cpu, ¶ms->common.monitored_cpus)) - account_ipi(tool, dst_cpu); + account_ipi(tool, dst_cpu); return 0; }
@@ -346,6 +342,11 @@ osnoise_ipi_cpumask_handler(struct trace_seq *s, struct tep_record *record, return 0; } + /* + * Despite already filtering for such an intersection, we need to compute + * the intersection here as the @cpumask field may contain non-monitored + * CPUs. + */ CPU_AND(&cpumask_tmp_cpus, event_cpus, ¶ms->common.monitored_cpus); /*
@@ -398,6 +399,33 @@ struct osnoise_tool *osnoise_init_top(struct common_params *params) goto out_err; } + /* + * If tracing on a subset of possible CPUs, leverage the kernel filtering + * infrastructure to only generate events on traced CPUs. + */ + if (params->cpus) { + char filter[MAX_PATH]; + + snprintf(filter, ARRAY_SIZE(filter), "cpu & CPUS{%s}\n", params->cpus); + retval = tracefs_event_file_write(tool->trace.inst, + "ipi", "ipi_send_cpu", "filter", + filter); + if (retval < 0) { + err_msg("Could not set ipi_send_cpu CPU filter\n"); + goto out_err; + } + + + snprintf(filter, ARRAY_SIZE(filter), "cpumask & CPUS{%s}\n", params->cpus); + retval = tracefs_event_file_write(tool->trace.inst, + "ipi", "ipi_send_cpumask", "filter", + filter); + if (retval < 0) { + err_msg("Could not set ipi_send_cpumask CPU filter\n"); + goto out_err; + } + } + tep_register_event_handler(tool->trace.tep, -1, "ipi", "ipi_send_cpu", osnoise_ipi_cpu_handler, NULL);
--
2.55.0