On 26/03/21 11:33, Peter Zijlstra wrote:
> Stop polluting sysctl, move to debugfs for SCHED_DEBUG stuff.
>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> ---
> kernel/sched/debug.c | 255
> ++++++++++--------------------------------------
> kernel/sched/sched.h | 2
> kernel/sched/topology.c | 1
> 3 files changed, 59 insertions(+), 199 deletions(-)
>
I do very much like to see a simple pair of seq_puts() replacing the
mess I put in there!
One comment below.
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> +void register_sched_domain_sysctl(void)
> +{
> + int cpu, i;
>
> if (!cpumask_available(sd_sysctl_cpus)) {
> if (!alloc_cpumask_var(&sd_sysctl_cpus, GFP_KERNEL))
> return;
> - }
> -
> - if (!init_done) {
> - init_done = true;
> - /* init to possible to not have holes in @cpu_entries */
> cpumask_copy(sd_sysctl_cpus, cpu_possible_mask);
> }
>
> - for_each_cpu(i, sd_sysctl_cpus) {
> - struct ctl_table *e = cpu_idx[i];
> + if (!sd_dentry)
> + sd_dentry = debugfs_create_dir("domains", debugfs_sched);
>
> - if (e->child)
> - sd_free_ctl_entry(&e->child);
> + for_each_cpu(cpu, sd_sysctl_cpus) {
> + struct sched_domain *sd;
> + struct dentry *d_cpu;
> + char buf[32];
> +
> + snprintf(buf, sizeof(buf), "cpu%d", cpu);
> + debugfs_remove(debugfs_lookup(buf, sd_dentry));
> + d_cpu = debugfs_create_dir(buf, sd_dentry);
> +
> + i = 0;
> + for_each_domain(cpu, sd) {
> + struct dentry *d_sd;
>
> - if (!e->procname) {
> - snprintf(buf, 32, "cpu%d", i);
> - e->procname = kstrdup(buf, GFP_KERNEL);
> - }
> - e->mode = 0555;
> - e->child = sd_alloc_ctl_cpu_table(i);
> + snprintf(buf, sizeof(buf), "domain%d", i);
> + d_sd = debugfs_create_dir(buf, d_cpu);
>
> - __cpumask_clear_cpu(i, sd_sysctl_cpus);
That seems to be the only place we cleared a CPU in that cpumask, and I
don't see its replacement, which would go against:
bbdacdfed2f5 ("sched/debug: Optimize sched_domain sysctl generation")
With my very limited understanding of debugfs and sysctl, it seems that
before we would have some stuff saved in sd_ctl_table and free/reinit just
the bits we needed. With debugfs_remove(), I think we wipe everything
clean, or did I read that wrong?
