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scx_bpfland: expose the amount of online CPUs

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Periodically report the amount of online CPUs to stdout.

The online CPUs are initially evaluated looking at the online cpumask,
then the value is updated in the .cpu_offline() / .cpu_online()
callbacks.

Tested-by: Piotr Gorski <lucjan.lucjanov@gmail.com>
Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
This commit is contained in:
Andrea Righi 2024-07-10 14:05:47 +02:00
parent 3a47b484af
commit f59aa52fe7
2 changed files with 32 additions and 2 deletions
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32
scheds/rust/scx_bpfland/src/bpf/main.bpf.c
View File

@ -84,7 +84,7 @@ volatile u64 nr_direct_dispatches, nr_kthread_dispatches,
/* /*
* Amount of currently running tasks. * Amount of currently running tasks.
*/ */
volatile u64 nr_running, nr_interactive; volatile u64 nr_running, nr_interactive, nr_online_cpus;
/* /*
* Exit information. * Exit information.
@ -682,12 +682,16 @@ void BPF_STRUCT_OPS(bpfland_cpu_online, s32 cpu)
{ {
/* Set the CPU state to offline */ /* Set the CPU state to offline */
set_cpu_state(offline_cpumask, cpu, false); set_cpu_state(offline_cpumask, cpu, false);
__sync_fetch_and_add(&nr_online_cpus, 1);
} }
void BPF_STRUCT_OPS(bpfland_cpu_offline, s32 cpu) void BPF_STRUCT_OPS(bpfland_cpu_offline, s32 cpu)
{ {
/* Set the CPU state to online */ /* Set the CPU state to online */
set_cpu_state(offline_cpumask, cpu, true); set_cpu_state(offline_cpumask, cpu, true);
__sync_fetch_and_sub(&nr_online_cpus, 1);
} }
s32 BPF_STRUCT_OPS(bpfland_init_task, struct task_struct *p, s32 BPF_STRUCT_OPS(bpfland_init_task, struct task_struct *p,
@ -700,12 +704,38 @@ s32 BPF_STRUCT_OPS(bpfland_init_task, struct task_struct *p,
return -ENOMEM; return -ENOMEM;
} }
/*
* Evaluate the amount of online CPUs.
*/
s32 get_nr_online_cpus(void)
{
const struct cpumask *online_cpumask;
u64 cpu_max = scx_bpf_nr_cpu_ids();
int i, cpus = 0;
cpu_max = scx_bpf_nr_cpu_ids();
online_cpumask = scx_bpf_get_online_cpumask();
bpf_for(i, 0, cpu_max) {
if (!bpf_cpumask_test_cpu(i, online_cpumask))
continue;
cpus++;
}
scx_bpf_put_cpumask(online_cpumask);
return cpus;
}
s32 BPF_STRUCT_OPS_SLEEPABLE(bpfland_init) s32 BPF_STRUCT_OPS_SLEEPABLE(bpfland_init)
{ {
struct bpf_cpumask *mask; struct bpf_cpumask *mask;
int err; int err;
s32 cpu; s32 cpu;
/* Initialize amount of online CPUs */
nr_online_cpus = get_nr_online_cpus();
/* Create per-CPU DSQs (used to dispatch tasks directly on a CPU) */ /* Create per-CPU DSQs (used to dispatch tasks directly on a CPU) */
bpf_for(cpu, 0, MAX_CPUS) { bpf_for(cpu, 0, MAX_CPUS) {
err = scx_bpf_create_dsq(cpu_to_dsq(cpu), -1); err = scx_bpf_create_dsq(cpu_to_dsq(cpu), -1);

2
scheds/rust/scx_bpfland/src/main.rs
View File

@ -205,7 +205,7 @@ impl<'a> Scheduler<'a> {
} }
fn update_stats(&mut self) { fn update_stats(&mut self) {
let nr_cpus = libbpf_rs::num_possible_cpus().unwrap(); let nr_cpus = self.skel.bss().nr_online_cpus;
let nr_running = self.skel.bss().nr_running; let nr_running = self.skel.bss().nr_running;
let nr_interactive = self.skel.bss().nr_interactive; let nr_interactive = self.skel.bss().nr_interactive;
let nr_kthread_dispatches = self.skel.bss().nr_kthread_dispatches; let nr_kthread_dispatches = self.skel.bss().nr_kthread_dispatches;