Re: [PATCH] Add a sysctl for numa_balancing.

Will Huck
2013-04-25T00:14:14Z

On 04/25/2013 07:56 AM, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> As discussed earlier, this adds a working sysctl to enable/disable
> automatic numa memory balancing at runtime.
>
> This was possible earlier through debugfs, but only with special
> debugging options set. Also fix the boot message.

One offline question.

If I configure uma to fake numa, is there benefit or downside?

>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> Documentation/sysctl/kernel.txt | 10 ++++++++++
> include/linux/sched/sysctl.h | 4 ++++
> kernel/sched/core.c | 24 +++++++++++++++++++++++-
> kernel/sysctl.c | 11 +++++++++++
> mm/mempolicy.c | 2 +-
> 5 files changed, 49 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
> index ccd4258..17a7004 100644
> --- a/Documentation/sysctl/kernel.txt
> +++ b/Documentation/sysctl/kernel.txt
> @@ -354,6 +354,16 @@ utilize.
>
> ==============================================================
>
> +numa_balancing
> +
> +Enables/disables automatic page fault based NUMA memory
> +balancing. Memory is moved automatically to nodes
> +that access it often.
> +
> +TBD someone document the other numa_balancing tunables
> +
> +==============================================================
> +
> osrelease, ostype & version:
>
> # cat osrelease
> diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
> index bf8086b..e228a1b 100644
> --- a/include/linux/sched/sysctl.h
> +++ b/include/linux/sched/sysctl.h
> @@ -101,4 +101,8 @@ extern int sched_rt_handler(struct ctl_table *table, int write,
> void __user *buffer, size_t *lenp,
> loff_t *ppos);
>
> +extern int sched_numa_balancing(struct ctl_table *table, int write,
> + void __user *buffer, size_t *lenp,
> + loff_t *ppos);
> +
> #endif /* _SCHED_SYSCTL_H */
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 67d0465..679be74 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1614,7 +1614,29 @@ void set_numabalancing_state(bool enabled)
> numabalancing_enabled = enabled;
> }
> #endif /* CONFIG_SCHED_DEBUG */
> -#endif /* CONFIG_NUMA_BALANCING */
> +
> +#ifdef CONFIG_PROC_SYSCTL
> +int sched_numa_balancing(struct ctl_table *table, int write,
> + void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> + struct ctl_table t;
> + int err;
> + int state = numabalancing_enabled;
> +
> + if (write && !capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + t = *table;
> + t.data = &state;
> + err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
> + if (err < 0)
> + return err;
> + if (write)
> + set_numabalancing_state(state);
> + return err;
> +}
> +#endif
> +#endif
>
> /*
> * fork()/clone()-time setup:
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index afc1dc6..94164ac 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -393,6 +393,17 @@ static struct ctl_table kern_table[] = {
> .mode = 0644,
> .proc_handler = proc_dointvec,
> },
> + {
> + .procname = "numa_balancing",
> + .data = NULL, /* filled in by handler */
> + .maxlen = sizeof(unsigned int),
> + .mode = 0644,
> + .proc_handler = sched_numa_balancing,
> + .extra1 = &zero,
> + .extra2 = &one,
> + },
> +
> +
> #endif /* CONFIG_NUMA_BALANCING */
> #endif /* CONFIG_SCHED_DEBUG */
> {
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 7431001..7eee646 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2531,7 +2531,7 @@ static void __init check_numabalancing_enable(void)
>
> if (nr_node_ids > 1 && !numabalancing_override) {
> printk(KERN_INFO "Enabling automatic NUMA balancing. "
> - "Configure with numa_balancing= or sysctl");
> + "Configure with numa_balancing= or the kernel.numa_balancing sysctl");
> set_numabalancing_state(numabalancing_default);
> }
> }