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Message-ID: <20250920005931.2753828-8-tj@kernel.org>
Date: Fri, 19 Sep 2025 14:58:30 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com,
arighi@...dia.com,
multics69@...il.com
Cc: linux-kernel@...r.kernel.org,
sched-ext@...ts.linux.dev,
memxor@...il.com,
bpf@...r.kernel.org,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 07/46] tools/sched_ext: scx_qmap: Make debug output quieter by default
scx_qmap currently outputs verbose debug messages including cgroup operations
and CPU online/offline events by default, which can be noisy during normal
operation. While the existing -P option controls DSQ dumps and event
statistics, there's no way to suppress the other debug messages.
Split the debug output controls to make scx_qmap quieter by default. The -P
option continues to control DSQ dumps and event statistics
(print_dsqs_and_events), while a new -M option controls debug messages like
cgroup operations and CPU events (print_msgs). This allows users to run
scx_qmap with minimal output and selectively enable debug information as
needed.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
tools/sched_ext/scx_qmap.bpf.c | 80 +++++++++++++++++++---------------
tools/sched_ext/scx_qmap.c | 12 +++--
2 files changed, 53 insertions(+), 39 deletions(-)
diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
index cd50a94326e3..3072b593f898 100644
--- a/tools/sched_ext/scx_qmap.bpf.c
+++ b/tools/sched_ext/scx_qmap.bpf.c
@@ -39,7 +39,8 @@ const volatile u32 stall_kernel_nth;
const volatile u32 dsp_inf_loop_after;
const volatile u32 dsp_batch;
const volatile bool highpri_boosting;
-const volatile bool print_shared_dsq;
+const volatile bool print_dsqs_and_events;
+const volatile bool print_msgs;
const volatile s32 disallow_tgid;
const volatile bool suppress_dump;
@@ -633,22 +634,25 @@ void BPF_STRUCT_OPS(qmap_dump_task, struct scx_dump_ctx *dctx, struct task_struc
s32 BPF_STRUCT_OPS(qmap_cgroup_init, struct cgroup *cgrp, struct scx_cgroup_init_args *args)
{
- bpf_printk("CGRP INIT %llu weight=%u period=%lu quota=%ld burst=%lu",
- cgrp->kn->id, args->weight, args->bw_period_us,
- args->bw_quota_us, args->bw_burst_us);
+ if (print_msgs)
+ bpf_printk("CGRP INIT %llu weight=%u period=%lu quota=%ld burst=%lu",
+ cgrp->kn->id, args->weight, args->bw_period_us,
+ args->bw_quota_us, args->bw_burst_us);
return 0;
}
void BPF_STRUCT_OPS(qmap_cgroup_set_weight, struct cgroup *cgrp, u32 weight)
{
- bpf_printk("CGRP SET %llu weight=%u", cgrp->kn->id, weight);
+ if (print_msgs)
+ bpf_printk("CGRP SET %llu weight=%u", cgrp->kn->id, weight);
}
void BPF_STRUCT_OPS(qmap_cgroup_set_bandwidth, struct cgroup *cgrp,
u64 period_us, u64 quota_us, u64 burst_us)
{
- bpf_printk("CGRP SET %llu period=%lu quota=%ld burst=%lu", cgrp->kn->id,
- period_us, quota_us, burst_us);
+ if (print_msgs)
+ bpf_printk("CGRP SET %llu period=%lu quota=%ld burst=%lu",
+ cgrp->kn->id, period_us, quota_us, burst_us);
}
/*
@@ -692,16 +696,20 @@ static void print_cpus(void)
void BPF_STRUCT_OPS(qmap_cpu_online, s32 cpu)
{
- bpf_printk("CPU %d coming online", cpu);
- /* @cpu is already online at this point */
- print_cpus();
+ if (print_msgs) {
+ bpf_printk("CPU %d coming online", cpu);
+ /* @cpu is already online at this point */
+ print_cpus();
+ }
}
void BPF_STRUCT_OPS(qmap_cpu_offline, s32 cpu)
{
- bpf_printk("CPU %d going offline", cpu);
- /* @cpu is still online at this point */
- print_cpus();
+ if (print_msgs) {
+ bpf_printk("CPU %d going offline", cpu);
+ /* @cpu is still online at this point */
+ print_cpus();
+ }
}
struct monitor_timer {
@@ -799,35 +807,36 @@ static void dump_shared_dsq(void)
static int monitor_timerfn(void *map, int *key, struct bpf_timer *timer)
{
- struct scx_event_stats events;
-
bpf_rcu_read_lock();
dispatch_highpri(true);
bpf_rcu_read_unlock();
monitor_cpuperf();
- if (print_shared_dsq)
+ if (print_dsqs_and_events) {
+ struct scx_event_stats events;
+
dump_shared_dsq();
- __COMPAT_scx_bpf_events(&events, sizeof(events));
-
- bpf_printk("%35s: %lld", "SCX_EV_SELECT_CPU_FALLBACK",
- scx_read_event(&events, SCX_EV_SELECT_CPU_FALLBACK));
- bpf_printk("%35s: %lld", "SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE",
- scx_read_event(&events, SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE));
- bpf_printk("%35s: %lld", "SCX_EV_DISPATCH_KEEP_LAST",
- scx_read_event(&events, SCX_EV_DISPATCH_KEEP_LAST));
- bpf_printk("%35s: %lld", "SCX_EV_ENQ_SKIP_EXITING",
- scx_read_event(&events, SCX_EV_ENQ_SKIP_EXITING));
- bpf_printk("%35s: %lld", "SCX_EV_REFILL_SLICE_DFL",
- scx_read_event(&events, SCX_EV_REFILL_SLICE_DFL));
- bpf_printk("%35s: %lld", "SCX_EV_BYPASS_DURATION",
- scx_read_event(&events, SCX_EV_BYPASS_DURATION));
- bpf_printk("%35s: %lld", "SCX_EV_BYPASS_DISPATCH",
- scx_read_event(&events, SCX_EV_BYPASS_DISPATCH));
- bpf_printk("%35s: %lld", "SCX_EV_BYPASS_ACTIVATE",
- scx_read_event(&events, SCX_EV_BYPASS_ACTIVATE));
+ __COMPAT_scx_bpf_events(&events, sizeof(events));
+
+ bpf_printk("%35s: %lld", "SCX_EV_SELECT_CPU_FALLBACK",
+ scx_read_event(&events, SCX_EV_SELECT_CPU_FALLBACK));
+ bpf_printk("%35s: %lld", "SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE",
+ scx_read_event(&events, SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE));
+ bpf_printk("%35s: %lld", "SCX_EV_DISPATCH_KEEP_LAST",
+ scx_read_event(&events, SCX_EV_DISPATCH_KEEP_LAST));
+ bpf_printk("%35s: %lld", "SCX_EV_ENQ_SKIP_EXITING",
+ scx_read_event(&events, SCX_EV_ENQ_SKIP_EXITING));
+ bpf_printk("%35s: %lld", "SCX_EV_REFILL_SLICE_DFL",
+ scx_read_event(&events, SCX_EV_REFILL_SLICE_DFL));
+ bpf_printk("%35s: %lld", "SCX_EV_BYPASS_DURATION",
+ scx_read_event(&events, SCX_EV_BYPASS_DURATION));
+ bpf_printk("%35s: %lld", "SCX_EV_BYPASS_DISPATCH",
+ scx_read_event(&events, SCX_EV_BYPASS_DISPATCH));
+ bpf_printk("%35s: %lld", "SCX_EV_BYPASS_ACTIVATE",
+ scx_read_event(&events, SCX_EV_BYPASS_ACTIVATE));
+ }
bpf_timer_start(timer, ONE_SEC_IN_NS, 0);
return 0;
@@ -839,7 +848,8 @@ s32 BPF_STRUCT_OPS_SLEEPABLE(qmap_init)
struct bpf_timer *timer;
s32 ret;
- print_cpus();
+ if (print_msgs)
+ print_cpus();
ret = scx_bpf_create_dsq(SHARED_DSQ, -1);
if (ret)
diff --git a/tools/sched_ext/scx_qmap.c b/tools/sched_ext/scx_qmap.c
index c4912ab2e76f..ef701d45ba43 100644
--- a/tools/sched_ext/scx_qmap.c
+++ b/tools/sched_ext/scx_qmap.c
@@ -20,7 +20,7 @@ const char help_fmt[] =
"See the top-level comment in .bpf.c for more details.\n"
"\n"
"Usage: %s [-s SLICE_US] [-e COUNT] [-t COUNT] [-T COUNT] [-l COUNT] [-b COUNT]\n"
-" [-P] [-d PID] [-D LEN] [-p] [-v]\n"
+" [-P] [-M] [-d PID] [-D LEN] [-p] [-v]\n"
"\n"
" -s SLICE_US Override slice duration\n"
" -e COUNT Trigger scx_bpf_error() after COUNT enqueues\n"
@@ -28,7 +28,8 @@ const char help_fmt[] =
" -T COUNT Stall every COUNT'th kernel thread\n"
" -l COUNT Trigger dispatch infinite looping after COUNT dispatches\n"
" -b COUNT Dispatch upto COUNT tasks together\n"
-" -P Print out DSQ content to trace_pipe every second, use with -b\n"
+" -P Print out DSQ content and event counters to trace_pipe every second\n"
+" -M Print out debug messages to trace_pipe\n"
" -H Boost nice -20 tasks in SHARED_DSQ, use with -b\n"
" -d PID Disallow a process from switching into SCHED_EXT (-1 for self)\n"
" -D LEN Set scx_exit_info.dump buffer length\n"
@@ -66,7 +67,7 @@ int main(int argc, char **argv)
skel->rodata->slice_ns = __COMPAT_ENUM_OR_ZERO("scx_public_consts", "SCX_SLICE_DFL");
- while ((opt = getopt(argc, argv, "s:e:t:T:l:b:PHd:D:Spvh")) != -1) {
+ while ((opt = getopt(argc, argv, "s:e:t:T:l:b:PMHd:D:Spvh")) != -1) {
switch (opt) {
case 's':
skel->rodata->slice_ns = strtoull(optarg, NULL, 0) * 1000;
@@ -87,7 +88,10 @@ int main(int argc, char **argv)
skel->rodata->dsp_batch = strtoul(optarg, NULL, 0);
break;
case 'P':
- skel->rodata->print_shared_dsq = true;
+ skel->rodata->print_dsqs_and_events = true;
+ break;
+ case 'M':
+ skel->rodata->print_msgs = true;
break;
case 'H':
skel->rodata->highpri_boosting = true;
--
2.51.0
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