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authorLeonardo Bras <leobras@redhat.com>2023-06-15 03:59:47 -0300
committerPeter Zijlstra <peterz@infradead.org>2023-06-16 22:08:09 +0200
commitbf5a8c26ad7caf0772a1cd48c8a0924e48bdbaf0 (patch)
tree0e8804f544d27fc4f249ff9a36b3434eb5973519 /kernel/smp.c
parent949fa3f11ced2a5c8e3737e73b09676adf4b322b (diff)
trace,smp: Add tracepoints for scheduling remotelly called functions
Add a tracepoint for when a CSD is queued to a remote CPU's call_single_queue. This allows finding exactly which CPU queued a given CSD when looking at a csd_function_{entry,exit} event, and also enables us to accurately measure IPI delivery time with e.g. a synthetic event: $ echo 'hist:keys=cpu,csd.hex:ts=common_timestamp.usecs' >\ /sys/kernel/tracing/events/smp/csd_queue_cpu/trigger $ echo 'csd_latency unsigned int dst_cpu; unsigned long csd; u64 time' >\ /sys/kernel/tracing/synthetic_events $ echo \ 'hist:keys=common_cpu,csd.hex:'\ 'time=common_timestamp.usecs-$ts:'\ 'onmatch(smp.csd_queue_cpu).trace(csd_latency,common_cpu,csd,$time)' >\ /sys/kernel/tracing/events/smp/csd_function_entry/trigger $ trace-cmd record -e 'synthetic:csd_latency' hackbench $ trace-cmd report <...>-467 [001] 21.824263: csd_queue_cpu: cpu=0 callsite=try_to_wake_up+0x2ea func=sched_ttwu_pending csd=0xffff8880076148b8 <...>-467 [001] 21.824280: ipi_send_cpu: cpu=0 callsite=try_to_wake_up+0x2ea callback=generic_smp_call_function_single_interrupt+0x0 <...>-489 [000] 21.824299: csd_function_entry: func=sched_ttwu_pending csd=0xffff8880076148b8 <...>-489 [000] 21.824320: csd_latency: dst_cpu=0, csd=18446612682193848504, time=36 Suggested-by: Valentin Schneider <vschneid@redhat.com> Signed-off-by: Leonardo Bras <leobras@redhat.com> Tested-and-reviewed-by: Valentin Schneider <vschneid@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20230615065944.188876-7-leobras@redhat.com
Diffstat (limited to 'kernel/smp.c')
-rw-r--r--kernel/smp.c16
1 files changed, 5 insertions, 11 deletions
diff --git a/kernel/smp.c b/kernel/smp.c
index 1fa01a83fd83..385179dae360 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -340,7 +340,7 @@ void __smp_call_single_queue(int cpu, struct llist_node *node)
* even if we haven't sent the smp_call IPI yet (e.g. the stopper
* executes migration_cpu_stop() on the remote CPU).
*/
- if (trace_ipi_send_cpu_enabled()) {
+ if (trace_csd_queue_cpu_enabled()) {
call_single_data_t *csd;
smp_call_func_t func;
@@ -348,7 +348,7 @@ void __smp_call_single_queue(int cpu, struct llist_node *node)
func = CSD_TYPE(csd) == CSD_TYPE_TTWU ?
sched_ttwu_pending : csd->func;
- trace_ipi_send_cpu(cpu, _RET_IP_, func);
+ trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);
}
/*
@@ -741,7 +741,7 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
int cpu, last_cpu, this_cpu = smp_processor_id();
struct call_function_data *cfd;
bool wait = scf_flags & SCF_WAIT;
- int nr_cpus = 0, nr_queued = 0;
+ int nr_cpus = 0;
bool run_remote = false;
bool run_local = false;
@@ -799,22 +799,16 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
csd->node.src = smp_processor_id();
csd->node.dst = cpu;
#endif
+ trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);
+
if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) {
__cpumask_set_cpu(cpu, cfd->cpumask_ipi);
nr_cpus++;
last_cpu = cpu;
}
- nr_queued++;
}
/*
- * Trace each smp_function_call_*() as an IPI, actual IPIs
- * will be traced with func==generic_smp_call_function_single_ipi().
- */
- if (nr_queued)
- trace_ipi_send_cpumask(cfd->cpumask, _RET_IP_, func);
-
- /*
* Choose the most efficient way to send an IPI. Note that the
* number of CPUs might be zero due to concurrent changes to the
* provided mask.