On Fri, Feb 14, 2025 at 08:40:07PM +0100, Andrea Righi wrote:
> Introduce a new kfunc to retrieve the node associated to a CPU:
>
> int scx_bpf_cpu_node(s32 cpu)
>
> Add the following kfuncs to provide BPF schedulers direct access to
> per-node idle cpumasks information:
>
> const struct cpumask *scx_bpf_get_idle_cpumask_node(int node)
> const struct cpumask *scx_bpf_get_idle_smtmask_node(int node)
> s32 scx_bpf_pick_idle_cpu_in_node(const cpumask_t *cpus_allowed,
> int node, u64 flags)
> s32 scx_bpf_pick_any_cpu_node(const cpumask_t *cpus_allowed,
> int node, u64 flags)
>
> Moreover, trigger an scx error when any of the non-node aware idle CPU
> kfuncs are used when SCX_OPS_BUILTIN_IDLE_PER_NODE is enabled.
>
> Cc: Yury Norov [NVIDIA] <yury.norov@xxxxxxxxx>
> Signed-off-by: Andrea Righi <arighi@xxxxxxxxxx>
Reviewed-by: Yury Norov [NVIDIA] <yury.norov@xxxxxxxxx>
> ---
> kernel/sched/ext_idle.c | 180 +++++++++++++++++++++++
> tools/sched_ext/include/scx/common.bpf.h | 5 +
> tools/sched_ext/include/scx/compat.bpf.h | 31 ++++
> 3 files changed, 216 insertions(+)
>
> diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c
> index 8dacccc82ed63..5c062affd622c 100644
> --- a/kernel/sched/ext_idle.c
> +++ b/kernel/sched/ext_idle.c
> @@ -728,6 +728,33 @@ void scx_idle_disable(void)
> /********************************************************************************
> * Helpers that can be called from the BPF scheduler.
> */
> +
> +static int validate_node(int node)
> +{
> + if (!static_branch_likely(&scx_builtin_idle_per_node)) {
> + scx_ops_error("per-node idle tracking is disabled");
> + return -EOPNOTSUPP;
> + }
> +
> + /* Return no entry for NUMA_NO_NODE (not a critical scx error) */
> + if (node == NUMA_NO_NODE)
> + return -ENOENT;
> +
> + /* Make sure node is in a valid range */
> + if (node < 0 || node >= nr_node_ids) {
> + scx_ops_error("invalid node %d", node);
> + return -EINVAL;
> + }
> +
> + /* Make sure the node is part of the set of possible nodes */
> + if (!node_possible(node)) {
> + scx_ops_error("unavailable node %d", node);
> + return -EINVAL;
> + }
> +
> + return node;
> +}
> +
> __bpf_kfunc_start_defs();
>
> static bool check_builtin_idle_enabled(void)
> @@ -739,6 +766,23 @@ static bool check_builtin_idle_enabled(void)
> return false;
> }
>
> +/**
> + * scx_bpf_cpu_node - Return the NUMA node the given @cpu belongs to, or
> + * trigger an error if @cpu is invalid
> + * @cpu: target CPU
> + */
> +__bpf_kfunc int scx_bpf_cpu_node(s32 cpu)
> +{
> +#ifdef CONFIG_NUMA
> + if (!ops_cpu_valid(cpu, NULL))
> + return NUMA_NO_NODE;
> +
> + return cpu_to_node(cpu);
> +#else
> + return 0;
> +#endif
> +}
> +
> /**
> * scx_bpf_select_cpu_dfl - The default implementation of ops.select_cpu()
> * @p: task_struct to select a CPU for
> @@ -771,6 +815,27 @@ __bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
> return prev_cpu;
> }
>
> +/**
> + * scx_bpf_get_idle_cpumask_node - Get a referenced kptr to the
> + * idle-tracking per-CPU cpumask of a target NUMA node.
> + *
> + * Returns an empty cpumask if idle tracking is not enabled, if @node is
> + * not valid, or running on a UP kernel. In this case the actual error will
> + * be reported to the BPF scheduler via scx_ops_error().
> + */
> +__bpf_kfunc const struct cpumask *scx_bpf_get_idle_cpumask_node(int node)
> +{
> + node = validate_node(node);
> + if (node < 0)
> + return cpu_none_mask;
> +
> +#ifdef CONFIG_SMP
> + return idle_cpumask(node)->cpu;
> +#else
> + return cpu_none_mask;
> +#endif
Here you need to check for SMP at the beginning. That way you can
avoid calling validate_node() if SMP is disabled.
> +}
> +
> /**
> * scx_bpf_get_idle_cpumask - Get a referenced kptr to the idle-tracking
> * per-CPU cpumask.
> @@ -795,6 +860,31 @@ __bpf_kfunc const struct cpumask *scx_bpf_get_idle_cpumask(void)
> #endif
> }
>
> +/**
> + * scx_bpf_get_idle_smtmask_node - Get a referenced kptr to the
> + * idle-tracking, per-physical-core cpumask of a target NUMA node. Can be
> + * used to determine if an entire physical core is free.
> + *
> + * Returns an empty cpumask if idle tracking is not enabled, if @node is
> + * not valid, or running on a UP kernel. In this case the actual error will
> + * be reported to the BPF scheduler via scx_ops_error().
> + */
> +__bpf_kfunc const struct cpumask *scx_bpf_get_idle_smtmask_node(int node)
> +{
> + node = validate_node(node);
> + if (node < 0)
> + return cpu_none_mask;
> +
> +#ifdef CONFIG_SMP
> + if (sched_smt_active())
> + return idle_cpumask(node)->smt;
> + else
> + return idle_cpumask(node)->cpu;
> +#else
> + return cpu_none_mask;
> +#endif
Same here. It's minor. Don't thing it's worth another version.
Thanks,
Yury
> +}
> +
> /**
> * scx_bpf_get_idle_smtmask - Get a referenced kptr to the idle-tracking,
> * per-physical-core cpumask. Can be used to determine if an entire physical
> @@ -859,6 +949,35 @@ __bpf_kfunc bool scx_bpf_test_and_clear_cpu_idle(s32 cpu)
> return false;
> }
>
> +/**
> + * scx_bpf_pick_idle_cpu_in_node - Pick and claim an idle cpu from @node
> + * @cpus_allowed: Allowed cpumask
> + * @node: target NUMA node
> + * @flags: %SCX_PICK_IDLE_* flags
> + *
> + * Pick and claim an idle cpu in @cpus_allowed from the NUMA node @node.
> + *
> + * Returns the picked idle cpu number on success, or -%EBUSY if no matching
> + * cpu was found.
> + *
> + * The search starts from @node and proceeds to other online NUMA nodes in
> + * order of increasing distance (unless SCX_PICK_IDLE_IN_NODE is specified,
> + * in which case the search is limited to the target @node).
> + *
> + * Always returns an error if ops.update_idle() is implemented and
> + * %SCX_OPS_KEEP_BUILTIN_IDLE is not set, or if
> + * %SCX_OPS_BUILTIN_IDLE_PER_NODE is not set.
> + */
> +__bpf_kfunc s32 scx_bpf_pick_idle_cpu_in_node(const struct cpumask *cpus_allowed,
> + int node, u64 flags)
> +{
> + node = validate_node(node);
> + if (node < 0)
> + return node;
> +
> + return scx_pick_idle_cpu(cpus_allowed, node, flags);
> +}
> +
> /**
> * scx_bpf_pick_idle_cpu - Pick and claim an idle cpu
> * @cpus_allowed: Allowed cpumask
> @@ -877,16 +996,64 @@ __bpf_kfunc bool scx_bpf_test_and_clear_cpu_idle(s32 cpu)
> *
> * Unavailable if ops.update_idle() is implemented and
> * %SCX_OPS_KEEP_BUILTIN_IDLE is not set.
> + *
> + * Always returns an error if %SCX_OPS_BUILTIN_IDLE_PER_NODE is set, use
> + * scx_bpf_pick_idle_cpu_in_node() instead.
> */
> __bpf_kfunc s32 scx_bpf_pick_idle_cpu(const struct cpumask *cpus_allowed,
> u64 flags)
> {
> + if (static_branch_maybe(CONFIG_NUMA, &scx_builtin_idle_per_node)) {
> + scx_ops_error("per-node idle tracking is enabled");
> + return -EBUSY;
> + }
> +
> if (!check_builtin_idle_enabled())
> return -EBUSY;
>
> return scx_pick_idle_cpu(cpus_allowed, NUMA_NO_NODE, flags);
> }
>
> +/**
> + * scx_bpf_pick_any_cpu_in_node - Pick and claim an idle cpu if available
> + * or pick any CPU from @node
> + * @cpus_allowed: Allowed cpumask
> + * @node: target NUMA node
> + * @flags: %SCX_PICK_IDLE_CPU_* flags
> + *
> + * Pick and claim an idle cpu in @cpus_allowed. If none is available, pick any
> + * CPU in @cpus_allowed. Guaranteed to succeed and returns the picked idle cpu
> + * number if @cpus_allowed is not empty. -%EBUSY is returned if @cpus_allowed is
> + * empty.
> + *
> + * The search starts from @node and proceeds to other online NUMA nodes in
> + * order of increasing distance (unless SCX_PICK_IDLE_IN_NODE is specified,
> + * in which case the search is limited to the target @node).
> + *
> + * If ops.update_idle() is implemented and %SCX_OPS_KEEP_BUILTIN_IDLE is not
> + * set, this function can't tell which CPUs are idle and will always pick any
> + * CPU.
> + */
> +__bpf_kfunc s32 scx_bpf_pick_any_cpu_in_node(const struct cpumask *cpus_allowed,
> + int node, u64 flags)
> +{
> + s32 cpu;
> +
> + node = validate_node(node);
> + if (node < 0)
> + return node;
> +
> + cpu = scx_pick_idle_cpu(cpus_allowed, node, flags);
> + if (cpu >= 0)
> + return cpu;
> +
> + cpu = cpumask_any_distribute(cpus_allowed);
> + if (cpu < nr_cpu_ids)
> + return cpu;
> + else
> + return -EBUSY;
> +}
> +
> /**
> * scx_bpf_pick_any_cpu - Pick and claim an idle cpu if available or pick any CPU
> * @cpus_allowed: Allowed cpumask
> @@ -900,12 +1067,20 @@ __bpf_kfunc s32 scx_bpf_pick_idle_cpu(const struct cpumask *cpus_allowed,
> * If ops.update_idle() is implemented and %SCX_OPS_KEEP_BUILTIN_IDLE is not
> * set, this function can't tell which CPUs are idle and will always pick any
> * CPU.
> + *
> + * Always returns an error if %SCX_OPS_BUILTIN_IDLE_PER_NODE is set, use
> + * scx_bpf_pick_any_cpu_in_node() instead.
> */
> __bpf_kfunc s32 scx_bpf_pick_any_cpu(const struct cpumask *cpus_allowed,
> u64 flags)
> {
> s32 cpu;
>
> + if (static_branch_maybe(CONFIG_NUMA, &scx_builtin_idle_per_node)) {
> + scx_ops_error("per-node idle tracking is enabled");
> + return -EBUSY;
> + }
> +
> if (static_branch_likely(&scx_builtin_idle_enabled)) {
> cpu = scx_pick_idle_cpu(cpus_allowed, NUMA_NO_NODE, flags);
> if (cpu >= 0)
> @@ -922,11 +1097,16 @@ __bpf_kfunc s32 scx_bpf_pick_any_cpu(const struct cpumask *cpus_allowed,
> __bpf_kfunc_end_defs();
>
> BTF_KFUNCS_START(scx_kfunc_ids_idle)
> +BTF_ID_FLAGS(func, scx_bpf_cpu_node)
> +BTF_ID_FLAGS(func, scx_bpf_get_idle_cpumask_node, KF_ACQUIRE)
> BTF_ID_FLAGS(func, scx_bpf_get_idle_cpumask, KF_ACQUIRE)
> +BTF_ID_FLAGS(func, scx_bpf_get_idle_smtmask_node, KF_ACQUIRE)
> BTF_ID_FLAGS(func, scx_bpf_get_idle_smtmask, KF_ACQUIRE)
> BTF_ID_FLAGS(func, scx_bpf_put_idle_cpumask, KF_RELEASE)
> BTF_ID_FLAGS(func, scx_bpf_test_and_clear_cpu_idle)
> +BTF_ID_FLAGS(func, scx_bpf_pick_idle_cpu_in_node, KF_RCU)
> BTF_ID_FLAGS(func, scx_bpf_pick_idle_cpu, KF_RCU)
> +BTF_ID_FLAGS(func, scx_bpf_pick_any_cpu_in_node, KF_RCU)
> BTF_ID_FLAGS(func, scx_bpf_pick_any_cpu, KF_RCU)
> BTF_KFUNCS_END(scx_kfunc_ids_idle)
>
> diff --git a/tools/sched_ext/include/scx/common.bpf.h b/tools/sched_ext/include/scx/common.bpf.h
> index 77bbe0199a32c..cd1659c5d3f46 100644
> --- a/tools/sched_ext/include/scx/common.bpf.h
> +++ b/tools/sched_ext/include/scx/common.bpf.h
> @@ -71,14 +71,19 @@ u32 scx_bpf_cpuperf_cap(s32 cpu) __ksym __weak;
> u32 scx_bpf_cpuperf_cur(s32 cpu) __ksym __weak;
> void scx_bpf_cpuperf_set(s32 cpu, u32 perf) __ksym __weak;
> u32 scx_bpf_nr_cpu_ids(void) __ksym __weak;
> +int scx_bpf_cpu_node(s32 cpu) __ksym __weak;
> const struct cpumask *scx_bpf_get_possible_cpumask(void) __ksym __weak;
> const struct cpumask *scx_bpf_get_online_cpumask(void) __ksym __weak;
> void scx_bpf_put_cpumask(const struct cpumask *cpumask) __ksym __weak;
> +const struct cpumask *scx_bpf_get_idle_cpumask_node(int node) __ksym __weak;
> const struct cpumask *scx_bpf_get_idle_cpumask(void) __ksym;
> +const struct cpumask *scx_bpf_get_idle_smtmask_node(int node) __ksym __weak;
> const struct cpumask *scx_bpf_get_idle_smtmask(void) __ksym;
> void scx_bpf_put_idle_cpumask(const struct cpumask *cpumask) __ksym;
> bool scx_bpf_test_and_clear_cpu_idle(s32 cpu) __ksym;
> +s32 scx_bpf_pick_idle_cpu_in_node(const cpumask_t *cpus_allowed, int node, u64 flags) __ksym __weak;
> s32 scx_bpf_pick_idle_cpu(const cpumask_t *cpus_allowed, u64 flags) __ksym;
> +s32 scx_bpf_pick_any_cpu_in_node(const cpumask_t *cpus_allowed, int node, u64 flags) __ksym __weak;
> s32 scx_bpf_pick_any_cpu(const cpumask_t *cpus_allowed, u64 flags) __ksym;
> bool scx_bpf_task_running(const struct task_struct *p) __ksym;
> s32 scx_bpf_task_cpu(const struct task_struct *p) __ksym;
> diff --git a/tools/sched_ext/include/scx/compat.bpf.h b/tools/sched_ext/include/scx/compat.bpf.h
> index e5fa72f9bf22b..617ed0ec85dc4 100644
> --- a/tools/sched_ext/include/scx/compat.bpf.h
> +++ b/tools/sched_ext/include/scx/compat.bpf.h
> @@ -182,6 +182,37 @@ static inline bool __COMPAT_is_enq_cpu_selected(u64 enq_flags)
> scx_bpf_now() : \
> bpf_ktime_get_ns())
>
> +/*
> + *
> + * v6.15: Introduce NUMA-aware kfuncs to operate with per-node idle
> + * cpumasks.
> + *
> + * Preserve the following __COMPAT_scx_*_node macros until v6.17.
> + */
> +#define __COMPAT_scx_bpf_cpu_node(cpu) \
> + (bpf_ksym_exists(scx_bpf_cpu_node) ? \
> + scx_bpf_cpu_node(cpu) : 0)
> +
> +#define __COMPAT_scx_bpf_get_idle_cpumask_node(node) \
> + (bpf_ksym_exists(scx_bpf_get_idle_cpumask_node) ? \
> + scx_bpf_get_idle_cpumask_node(node) : \
> + scx_bpf_get_idle_cpumask()) \
> +
> +#define __COMPAT_scx_bpf_get_idle_smtmask_node(node) \
> + (bpf_ksym_exists(scx_bpf_get_idle_smtmask_node) ? \
> + scx_bpf_get_idle_smtmask_node(node) : \
> + scx_bpf_get_idle_smtmask())
> +
> +#define __COMPAT_scx_bpf_pick_idle_cpu_in_node(cpus_allowed, node, flags) \
> + (bpf_ksym_exists(scx_bpf_pick_idle_cpu_in_node) ? \
> + scx_bpf_pick_idle_cpu_in_node(cpus_allowed, node, flags) : \
> + scx_bpf_pick_idle_cpu(cpus_allowed, flags))
> +
> +#define __COMPAT_scx_bpf_pick_any_cpu_in_node(cpus_allowed, node, flags) \
> + (bpf_ksym_exists(scx_bpf_pick_any_cpu_in_node) ? \
> + scx_bpf_pick_any_cpu_in_node(cpus_allowed, node, flags) : \
> + scx_bpf_pick_any_cpu(cpus_allowed, flags))
> +
> /*
> * Define sched_ext_ops. This may be expanded to define multiple variants for
> * backward compatibility. See compat.h::SCX_OPS_LOAD/ATTACH().
> --
> 2.48.1
