On 2025-03-07 at 14:54:10 -0800, Tim Chen wrote:
> On Tue, 2025-02-25 at 22:00 +0800, Chen Yu wrote:
> > [Problem Statement]
> > Currently, NUMA balancing is configured system-wide. However,
> >
> >
> > A simple example to show how to use per-cgroup Numa balancing:
> >
> > Step1
> > //switch to global per cgroup Numa balancing,
> > //All cgroup's Numa balance is disabled by default.
> > echo 4 > /proc/sys/kernel/numa_balancing
> >
>
> Can you add documentation of this additional feature
> for numa_balancing in
> admin-guide/sysctl/kernel.rst
>
OK, will refine in next version.
> Should you make NUMA_BALANCING_NORMAL and NUMA_BALANCING_CGROUP
> mutually exclusive in? In other words
> echo 5 > /proc/sys/kernel/numa_balancing should result in numa_balancing to be 1?
>
> Otherwise tg_numa_balance_enabled() can return 0 with NUMA_BALANCING_CGROUP
> bit turned on even though you have NUMA_BALANCING_NORMAL bit on.
>
I see, will fix tg_numa_balance_enabled() in next version, thanks!
Best,
Chenyu
> Tim
> >
> > Suggested-by: Tim Chen <tim.c.chen@xxxxxxxxx>
> > Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
> > ---
> > include/linux/sched/sysctl.h | 1 +
> > kernel/sched/core.c | 32 ++++++++++++++++++++++++++++++++
> > kernel/sched/fair.c | 18 ++++++++++++++++++
> > kernel/sched/sched.h | 3 +++
> > mm/mprotect.c | 5 +++--
> > 5 files changed, 57 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
> > index 5a64582b086b..1e4d5a9ddb26 100644
> > --- a/include/linux/sched/sysctl.h
> > +++ b/include/linux/sched/sysctl.h
> > @@ -22,6 +22,7 @@ enum sched_tunable_scaling {
> > #define NUMA_BALANCING_DISABLED 0x0
> > #define NUMA_BALANCING_NORMAL 0x1
> > #define NUMA_BALANCING_MEMORY_TIERING 0x2
> > +#define NUMA_BALANCING_CGROUP 0x4
> >
> > #ifdef CONFIG_NUMA_BALANCING
> > extern int sysctl_numa_balancing_mode;
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index 44efc725054a..f4f048b3da68 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -10023,6 +10023,31 @@ static ssize_t cpu_max_write(struct kernfs_open_file *of,
> > }
> > #endif
> >
> > +#ifdef CONFIG_NUMA_BALANCING
> > +static DEFINE_MUTEX(numa_balance_mutex);
> > +static int numa_balance_write_u64(struct cgroup_subsys_state *css,
> > + struct cftype *cftype, u64 enable)
> > +{
> > + struct task_group *tg;
> > + int ret;
> > +
> > + guard(mutex)(&numa_balance_mutex);
> > + tg = css_tg(css);
> > + if (tg->nlb_enabled == enable)
> > + return 0;
> > +
> > + tg->nlb_enabled = enable;
> > +
> > + return ret;
> > +}
> > +
> > +static u64 numa_balance_read_u64(struct cgroup_subsys_state *css,
> > + struct cftype *cft)
> > +{
> > + return css_tg(css)->nlb_enabled;
> > +}
> > +#endif /* CONFIG_NUMA_BALANCING */
> > +
> > static struct cftype cpu_files[] = {
> > #ifdef CONFIG_GROUP_SCHED_WEIGHT
> > {
> > @@ -10071,6 +10096,13 @@ static struct cftype cpu_files[] = {
> > .seq_show = cpu_uclamp_max_show,
> > .write = cpu_uclamp_max_write,
> > },
> > +#endif
> > +#ifdef CONFIG_NUMA_BALANCING
> > + {
> > + .name = "numa_load_balance",
> > + .read_u64 = numa_balance_read_u64,
> > + .write_u64 = numa_balance_write_u64,
> > + },
> > #endif
> > { } /* terminate */
> > };
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 1c0ef435a7aa..526cb33b007c 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -3146,6 +3146,18 @@ void task_numa_free(struct task_struct *p, bool final)
> > }
> > }
> >
> > +/* return true if the task group has enabled the numa balance */
> > +static bool tg_numa_balance_enabled(struct task_struct *p)
> > +{
> > + struct task_group *tg = task_group(p);
> > +
> > + if (tg && (sysctl_numa_balancing_mode & NUMA_BALANCING_CGROUP) &&
> > + !tg->nlb_enabled)
> > + return false;
> > +
> > + return true;
> > +}
> > +
> > /*
> > * Got a PROT_NONE fault for a page on @node.
> > */
> > @@ -3174,6 +3186,9 @@ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
> > !cpupid_valid(last_cpupid)))
> > return;
> >
> > + if (!tg_numa_balance_enabled(p))
> > + return;
> > +
> > /* Allocate buffer to track faults on a per-node basis */
> > if (unlikely(!p->numa_faults)) {
> > int size = sizeof(*p->numa_faults) *
> > @@ -3596,6 +3611,9 @@ static void task_tick_numa(struct rq *rq, struct task_struct *curr)
> > if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work)
> > return;
> >
> > + if (!tg_numa_balance_enabled(curr))
> > + return;
> > +
> > /*
> > * Using runtime rather than walltime has the dual advantage that
> > * we (mostly) drive the selection from busy threads and that the
> > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> > index 38e0e323dda2..9f478fb2c03a 100644
> > --- a/kernel/sched/sched.h
> > +++ b/kernel/sched/sched.h
> > @@ -491,6 +491,9 @@ struct task_group {
> > /* Effective clamp values used for a task group */
> > struct uclamp_se uclamp[UCLAMP_CNT];
> > #endif
> > +#ifdef CONFIG_NUMA_BALANCING
> > + u64 nlb_enabled;
> > +#endif
> >
> > };
> >
> > diff --git a/mm/mprotect.c b/mm/mprotect.c
> > index 516b1d847e2c..ddaaf20ef94c 100644
> > --- a/mm/mprotect.c
> > +++ b/mm/mprotect.c
> > @@ -155,10 +155,11 @@ static long change_pte_range(struct mmu_gather *tlb,
> > toptier = node_is_toptier(nid);
> >
> > /*
> > - * Skip scanning top tier node if normal numa
> > + * Skip scanning top tier node if normal/cgroup numa
> > * balancing is disabled
> > */
> > - if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
> > + if (!(sysctl_numa_balancing_mode &
> > + (NUMA_BALANCING_CGROUP | NUMA_BALANCING_NORMAL)) &&
> > toptier)
> > continue;
> > if (folio_use_access_time(folio))
>
