/* Enable/disable NUMA aware optimizations */ static DEFINE_STATIC_KEY_FALSE(scx_selcpu_topo_numa);
/* * cpumasks to track idle CPUs within each NUMA node. * * If SCX_OPS_BUILTIN_IDLE_PER_NODE is not enabled, a single global cpumask * from is used to track all the idle CPUs in the system.
*/ struct scx_idle_cpus {
cpumask_var_t cpu;
cpumask_var_t smt;
};
/* * Global host-wide idle cpumasks (used when SCX_OPS_BUILTIN_IDLE_PER_NODE * is not enabled).
*/ staticstruct scx_idle_cpus scx_idle_global_masks;
/* * Return the idle masks associated to a target @node. * * NUMA_NO_NODE identifies the global idle cpumask.
*/ staticstruct scx_idle_cpus *idle_cpumask(int node)
{ return node == NUMA_NO_NODE ? &scx_idle_global_masks : scx_idle_node_masks[node];
}
/* * Returns the NUMA node ID associated with a @cpu, or NUMA_NO_NODE if * per-node idle cpumasks are disabled.
*/ staticint scx_cpu_node_if_enabled(int cpu)
{ if (!static_branch_maybe(CONFIG_NUMA, &scx_builtin_idle_per_node)) return NUMA_NO_NODE;
#ifdef CONFIG_SCHED_SMT /* * SMT mask should be cleared whether we can claim @cpu or not. The SMT * cluster is not wholly idle either way. This also prevents * scx_pick_idle_cpu() from getting caught in an infinite loop.
*/ if (sched_smt_active()) { conststruct cpumask *smt = cpu_smt_mask(cpu); struct cpumask *idle_smts = idle_cpumask(node)->smt;
/* * If offline, @cpu is not its own sibling and * scx_pick_idle_cpu() can get caught in an infinite loop as * @cpu is never cleared from the idle SMT mask. Ensure that * @cpu is eventually cleared. * * NOTE: Use cpumask_intersects() and cpumask_test_cpu() to * reduce memory writes, which may help alleviate cache * coherence pressure.
*/ if (cpumask_intersects(smt, idle_smts))
cpumask_andnot(idle_smts, idle_smts, smt); elseif (cpumask_test_cpu(cpu, idle_smts))
__cpumask_clear_cpu(cpu, idle_smts);
} #endif
/* * Pick an idle CPU in a specific NUMA node.
*/ static s32 pick_idle_cpu_in_node(conststruct cpumask *cpus_allowed, int node, u64 flags)
{ int cpu;
retry: if (sched_smt_active()) {
cpu = cpumask_any_and_distribute(idle_cpumask(node)->smt, cpus_allowed); if (cpu < nr_cpu_ids) goto found;
if (flags & SCX_PICK_IDLE_CORE) return -EBUSY;
}
cpu = cpumask_any_and_distribute(idle_cpumask(node)->cpu, cpus_allowed); if (cpu >= nr_cpu_ids) return -EBUSY;
found: if (scx_idle_test_and_clear_cpu(cpu)) return cpu; else goto retry;
}
#ifdef CONFIG_NUMA /* * Tracks nodes that have not yet been visited when searching for an idle * CPU across all available nodes.
*/ static DEFINE_PER_CPU(nodemask_t, per_cpu_unvisited);
/* * Search for an idle CPU across all nodes, excluding @node.
*/ static s32 pick_idle_cpu_from_online_nodes(conststruct cpumask *cpus_allowed, int node, u64 flags)
{
nodemask_t *unvisited;
s32 cpu = -EBUSY;
/* * Restrict the search to the online nodes (excluding the current * node that has been visited already).
*/
nodes_copy(*unvisited, node_states[N_ONLINE]);
node_clear(node, *unvisited);
/* * Traverse all nodes in order of increasing distance, starting * from @node. * * This loop is O(N^2), with N being the amount of NUMA nodes, * which might be quite expensive in large NUMA systems. However, * this complexity comes into play only when a scheduler enables * SCX_OPS_BUILTIN_IDLE_PER_NODE and it's requesting an idle CPU * without specifying a target NUMA node, so it shouldn't be a * bottleneck is most cases. * * As a future optimization we may want to cache the list of nodes * in a per-node array, instead of actually traversing them every * time.
*/
for_each_node_numadist(node, *unvisited) {
cpu = pick_idle_cpu_in_node(cpus_allowed, node, flags); if (cpu >= 0) break;
}
preempt_enable();
/* * Find an idle CPU in the system, starting from @node.
*/ static s32 scx_pick_idle_cpu(conststruct cpumask *cpus_allowed, int node, u64 flags)
{
s32 cpu;
/* * Always search in the starting node first (this is an * optimization that can save some cycles even when the search is * not limited to a single node).
*/
cpu = pick_idle_cpu_in_node(cpus_allowed, node, flags); if (cpu >= 0) return cpu;
/* * Stop the search if we are using only a single global cpumask * (NUMA_NO_NODE) or if the search is restricted to the first node * only.
*/ if (node == NUMA_NO_NODE || flags & SCX_PICK_IDLE_IN_NODE) return -EBUSY;
/* * Extend the search to the other online nodes.
*/ return pick_idle_cpu_from_online_nodes(cpus_allowed, node, flags);
}
/* * Return the amount of CPUs in the same LLC domain of @cpu (or zero if the LLC * domain is not defined).
*/ staticunsignedint llc_weight(s32 cpu)
{ struct sched_domain *sd;
sd = rcu_dereference(per_cpu(sd_llc, cpu)); if (!sd) return 0;
return sd->span_weight;
}
/* * Return the cpumask representing the LLC domain of @cpu (or NULL if the LLC * domain is not defined).
*/ staticstruct cpumask *llc_span(s32 cpu)
{ struct sched_domain *sd;
sd = rcu_dereference(per_cpu(sd_llc, cpu)); if (!sd) return NULL;
return sched_domain_span(sd);
}
/* * Return the amount of CPUs in the same NUMA domain of @cpu (or zero if the * NUMA domain is not defined).
*/ staticunsignedint numa_weight(s32 cpu)
{ struct sched_domain *sd; struct sched_group *sg;
sd = rcu_dereference(per_cpu(sd_numa, cpu)); if (!sd) return 0;
sg = sd->groups; if (!sg) return 0;
return sg->group_weight;
}
/* * Return the cpumask representing the NUMA domain of @cpu (or NULL if the NUMA * domain is not defined).
*/ staticstruct cpumask *numa_span(s32 cpu)
{ struct sched_domain *sd; struct sched_group *sg;
sd = rcu_dereference(per_cpu(sd_numa, cpu)); if (!sd) return NULL;
sg = sd->groups; if (!sg) return NULL;
return sched_group_span(sg);
}
/* * Return true if the LLC domains do not perfectly overlap with the NUMA * domains, false otherwise.
*/ staticbool llc_numa_mismatch(void)
{ int cpu;
/* * We need to scan all online CPUs to verify whether their scheduling * domains overlap. * * While it is rare to encounter architectures with asymmetric NUMA * topologies, CPU hotplugging or virtualized environments can result * in asymmetric configurations. * * For example: * * NUMA 0: * - LLC 0: cpu0..cpu7 * - LLC 1: cpu8..cpu15 [offline] * * NUMA 1: * - LLC 0: cpu16..cpu23 * - LLC 1: cpu24..cpu31 * * In this case, if we only check the first online CPU (cpu0), we might * incorrectly assume that the LLC and NUMA domains are fully * overlapping, which is incorrect (as NUMA 1 has two distinct LLC * domains).
*/
for_each_online_cpu(cpu) if (llc_weight(cpu) != numa_weight(cpu)) returntrue;
returnfalse;
}
/* * Initialize topology-aware scheduling. * * Detect if the system has multiple LLC or multiple NUMA domains and enable * cache-aware / NUMA-aware scheduling optimizations in the default CPU idle * selection policy. * * Assumption: the kernel's internal topology representation assumes that each * CPU belongs to a single LLC domain, and that each LLC domain is entirely * contained within a single NUMA node.
*/ void scx_idle_update_selcpu_topology(struct sched_ext_ops *ops)
{ bool enable_llc = false, enable_numa = false; unsignedint nr_cpus;
s32 cpu = cpumask_first(cpu_online_mask);
/* * Enable LLC domain optimization only when there are multiple LLC * domains among the online CPUs. If all online CPUs are part of a * single LLC domain, the idle CPU selection logic can choose any * online CPU without bias. * * Note that it is sufficient to check the LLC domain of the first * online CPU to determine whether a single LLC domain includes all * CPUs.
*/
rcu_read_lock();
nr_cpus = llc_weight(cpu); if (nr_cpus > 0) { if (nr_cpus < num_online_cpus())
enable_llc = true;
pr_debug("sched_ext: LLC=%*pb weight=%u\n",
cpumask_pr_args(llc_span(cpu)), llc_weight(cpu));
}
/* * Enable NUMA optimization only when there are multiple NUMA domains * among the online CPUs and the NUMA domains don't perfectly overlaps * with the LLC domains. * * If all CPUs belong to the same NUMA node and the same LLC domain, * enabling both NUMA and LLC optimizations is unnecessary, as checking * for an idle CPU in the same domain twice is redundant. * * If SCX_OPS_BUILTIN_IDLE_PER_NODE is enabled ignore the NUMA * optimization, as we would naturally select idle CPUs within * specific NUMA nodes querying the corresponding per-node cpumask.
*/ if (!(ops->flags & SCX_OPS_BUILTIN_IDLE_PER_NODE)) {
nr_cpus = numa_weight(cpu); if (nr_cpus > 0) { if (nr_cpus < num_online_cpus() && llc_numa_mismatch())
enable_numa = true;
pr_debug("sched_ext: NUMA=%*pb weight=%u\n",
cpumask_pr_args(numa_span(cpu)), nr_cpus);
}
}
rcu_read_unlock();
if (enable_llc)
static_branch_enable_cpuslocked(&scx_selcpu_topo_llc); else
static_branch_disable_cpuslocked(&scx_selcpu_topo_llc); if (enable_numa)
static_branch_enable_cpuslocked(&scx_selcpu_topo_numa); else
static_branch_disable_cpuslocked(&scx_selcpu_topo_numa);
}
/* * Return true if @p can run on all possible CPUs, false otherwise.
*/ staticinlinebool task_affinity_all(conststruct task_struct *p)
{ return p->nr_cpus_allowed >= num_possible_cpus();
}
/* * Built-in CPU idle selection policy: * * 1. Prioritize full-idle cores: * - always prioritize CPUs from fully idle cores (both logical CPUs are * idle) to avoid interference caused by SMT. * * 2. Reuse the same CPU: * - prefer the last used CPU to take advantage of cached data (L1, L2) and * branch prediction optimizations. * * 3. Pick a CPU within the same LLC (Last-Level Cache): * - if the above conditions aren't met, pick a CPU that shares the same * LLC, if the LLC domain is a subset of @cpus_allowed, to maintain * cache locality. * * 4. Pick a CPU within the same NUMA node, if enabled: * - choose a CPU from the same NUMA node, if the node cpumask is a * subset of @cpus_allowed, to reduce memory access latency. * * 5. Pick any idle CPU within the @cpus_allowed domain. * * Step 3 and 4 are performed only if the system has, respectively, * multiple LLCs / multiple NUMA nodes (see scx_selcpu_topo_llc and * scx_selcpu_topo_numa) and they don't contain the same subset of CPUs. * * If %SCX_OPS_BUILTIN_IDLE_PER_NODE is enabled, the search will always * begin in @prev_cpu's node and proceed to other nodes in order of * increasing distance. * * Return the picked CPU if idle, or a negative value otherwise. * * NOTE: tasks that can only run on 1 CPU are excluded by this logic, because * we never call ops.select_cpu() for them, see select_task_rq().
*/
s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags, conststruct cpumask *cpus_allowed, u64 flags)
{ conststruct cpumask *llc_cpus = NULL, *numa_cpus = NULL; conststruct cpumask *allowed = cpus_allowed ?: p->cpus_ptr; int node = scx_cpu_node_if_enabled(prev_cpu); bool is_prev_allowed;
s32 cpu;
preempt_disable();
/* * Check whether @prev_cpu is still within the allowed set. If not, * we can still try selecting a nearby CPU.
*/
is_prev_allowed = cpumask_test_cpu(prev_cpu, allowed);
/* * Determine the subset of CPUs usable by @p within @cpus_allowed.
*/ if (allowed != p->cpus_ptr) { struct cpumask *local_cpus = this_cpu_cpumask_var_ptr(local_idle_cpumask);
/* * This is necessary to protect llc_cpus.
*/
rcu_read_lock();
/* * Determine the subset of CPUs that the task can use in its * current LLC and node. * * If the task can run on all CPUs, use the node and LLC cpumasks * directly.
*/ if (static_branch_maybe(CONFIG_NUMA, &scx_selcpu_topo_numa)) { struct cpumask *local_cpus = this_cpu_cpumask_var_ptr(local_numa_idle_cpumask); conststruct cpumask *cpus = numa_span(prev_cpu);
/* * If WAKE_SYNC, try to migrate the wakee to the waker's CPU.
*/ if (wake_flags & SCX_WAKE_SYNC) { int waker_node;
/* * If the waker's CPU is cache affine and prev_cpu is idle, * then avoid a migration.
*/
cpu = smp_processor_id(); if (is_prev_allowed && cpus_share_cache(cpu, prev_cpu) &&
scx_idle_test_and_clear_cpu(prev_cpu)) {
cpu = prev_cpu; goto out_unlock;
}
/* * If the waker's local DSQ is empty, and the system is under * utilized, try to wake up @p to the local DSQ of the waker. * * Checking only for an empty local DSQ is insufficient as it * could give the wakee an unfair advantage when the system is * oversaturated. * * Checking only for the presence of idle CPUs is also * insufficient as the local DSQ of the waker could have tasks * piled up on it even if there is an idle core elsewhere on * the system.
*/
waker_node = cpu_to_node(cpu); if (!(current->flags & PF_EXITING) &&
cpu_rq(cpu)->scx.local_dsq.nr == 0 &&
(!(flags & SCX_PICK_IDLE_IN_NODE) || (waker_node == node)) &&
!cpumask_empty(idle_cpumask(waker_node)->cpu)) { if (cpumask_test_cpu(cpu, allowed)) goto out_unlock;
}
}
/* * If CPU has SMT, any wholly idle CPU is likely a better pick than * partially idle @prev_cpu.
*/ if (sched_smt_active()) { /* * Keep using @prev_cpu if it's part of a fully idle core.
*/ if (is_prev_allowed &&
cpumask_test_cpu(prev_cpu, idle_cpumask(node)->smt) &&
scx_idle_test_and_clear_cpu(prev_cpu)) {
cpu = prev_cpu; goto out_unlock;
}
/* * Search for any fully idle core in the same LLC domain.
*/ if (llc_cpus) {
cpu = pick_idle_cpu_in_node(llc_cpus, node, SCX_PICK_IDLE_CORE); if (cpu >= 0) goto out_unlock;
}
/* * Search for any fully idle core in the same NUMA node.
*/ if (numa_cpus) {
cpu = pick_idle_cpu_in_node(numa_cpus, node, SCX_PICK_IDLE_CORE); if (cpu >= 0) goto out_unlock;
}
/* * Search for any full-idle core usable by the task. * * If the node-aware idle CPU selection policy is enabled * (%SCX_OPS_BUILTIN_IDLE_PER_NODE), the search will always * begin in prev_cpu's node and proceed to other nodes in * order of increasing distance.
*/
cpu = scx_pick_idle_cpu(allowed, node, flags | SCX_PICK_IDLE_CORE); if (cpu >= 0) goto out_unlock;
/* * Give up if we're strictly looking for a full-idle SMT * core.
*/ if (flags & SCX_PICK_IDLE_CORE) {
cpu = -EBUSY; goto out_unlock;
}
}
/* * Use @prev_cpu if it's idle.
*/ if (is_prev_allowed && scx_idle_test_and_clear_cpu(prev_cpu)) {
cpu = prev_cpu; goto out_unlock;
}
/* * Search for any idle CPU in the same LLC domain.
*/ if (llc_cpus) {
cpu = pick_idle_cpu_in_node(llc_cpus, node, 0); if (cpu >= 0) goto out_unlock;
}
/* * Search for any idle CPU in the same NUMA node.
*/ if (numa_cpus) {
cpu = pick_idle_cpu_in_node(numa_cpus, node, 0); if (cpu >= 0) goto out_unlock;
}
/* * Search for any idle CPU usable by the task. * * If the node-aware idle CPU selection policy is enabled * (%SCX_OPS_BUILTIN_IDLE_PER_NODE), the search will always begin * in prev_cpu's node and proceed to other nodes in order of * increasing distance.
*/
cpu = scx_pick_idle_cpu(allowed, node, flags);
if (idle) { /* * idle_smt handling is racy but that's fine as it's * only for optimization and self-correcting.
*/ if (!cpumask_subset(smt, idle_cpus)) return;
cpumask_or(idle_smts, idle_smts, smt);
} else {
cpumask_andnot(idle_smts, idle_smts, smt);
}
} #endif
}
/* * Update the idle state of a CPU to @idle. * * If @do_notify is true, ops.update_idle() is invoked to notify the scx * scheduler of an actual idle state transition (idle to busy or vice * versa). If @do_notify is false, only the idle state in the idle masks is * refreshed without invoking ops.update_idle(). * * This distinction is necessary, because an idle CPU can be "reserved" and * awakened via scx_bpf_pick_idle_cpu() + scx_bpf_kick_cpu(), marking it as * busy even if no tasks are dispatched. In this case, the CPU may return * to idle without a true state transition. Refreshing the idle masks * without invoking ops.update_idle() ensures accurate idle state tracking * while avoiding unnecessary updates and maintaining balanced state * transitions.
*/ void __scx_update_idle(struct rq *rq, bool idle, bool do_notify)
{ struct scx_sched *sch = scx_root; int cpu = cpu_of(rq);
lockdep_assert_rq_held(rq);
/* * Update the idle masks: * - for real idle transitions (do_notify == true) * - for idle-to-idle transitions (indicated by the previous task * being the idle thread, managed by pick_task_idle()) * * Skip updating idle masks if the previous task is not the idle * thread, since set_next_task_idle() has already handled it when * transitioning from a task to the idle thread (calling this * function with do_notify == true). * * In this way we can avoid updating the idle masks twice, * unnecessarily.
*/ if (static_branch_likely(&scx_builtin_idle_enabled)) if (do_notify || is_idle_task(rq->curr))
update_builtin_idle(cpu, idle);
/* * Trigger ops.update_idle() only when transitioning from a task to * the idle thread and vice versa. * * Idle transitions are indicated by do_notify being set to true, * managed by put_prev_task_idle()/set_next_task_idle(). * * This must come after builtin idle update so that BPF schedulers can * create interlocking between ops.update_idle() and ops.enqueue() - * either enqueue() sees the idle bit or update_idle() sees the task * that enqueue() queued.
*/ if (SCX_HAS_OP(sch, update_idle) && do_notify && !scx_rq_bypassing(rq))
SCX_CALL_OP(sch, SCX_KF_REST, update_idle, rq, cpu_of(rq), idle);
}
staticvoid reset_idle_masks(struct sched_ext_ops *ops)
{ int node;
/* * Consider all online cpus idle. Should converge to the actual state * quickly.
*/ if (!(ops->flags & SCX_OPS_BUILTIN_IDLE_PER_NODE)) {
cpumask_copy(idle_cpumask(NUMA_NO_NODE)->cpu, cpu_online_mask);
cpumask_copy(idle_cpumask(NUMA_NO_NODE)->smt, cpu_online_mask); return;
}
/******************************************************************************** * Helpers that can be called from the BPF scheduler.
*/
staticint validate_node(int node)
{ if (!static_branch_likely(&scx_builtin_idle_per_node)) {
scx_kf_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_kf_error("invalid node %d", node); return -EINVAL;
}
/* Make sure the node is part of the set of possible nodes */ if (!node_possible(node)) {
scx_kf_error("unavailable node %d", node); return -EINVAL;
}
return node;
}
__bpf_kfunc_start_defs();
staticbool check_builtin_idle_enabled(void)
{ if (static_branch_likely(&scx_builtin_idle_enabled)) returntrue;
scx_kf_error("built-in idle tracking is disabled"); returnfalse;
}
/* * Determine whether @p is a migration-disabled task in the context of BPF * code. * * We can't simply check whether @p->migration_disabled is set in a * sched_ext callback, because migration is always disabled for the current * task while running BPF code. * * The prolog (__bpf_prog_enter) and epilog (__bpf_prog_exit) respectively * disable and re-enable migration. For this reason, the current task * inside a sched_ext callback is always a migration-disabled task. * * Therefore, when @p->migration_disabled == 1, check whether @p is the * current task or not: if it is, then migration was not disabled before * entering the callback, otherwise migration was disabled. * * Returns true if @p is migration-disabled, false otherwise.
*/ staticbool is_bpf_migration_disabled(conststruct task_struct *p)
{ if (p->migration_disabled == 1) return p != current; else return p->migration_disabled;
}
if (!kf_cpu_valid(prev_cpu, NULL)) return -EINVAL;
if (!check_builtin_idle_enabled()) return -EBUSY;
/* * If called from an unlocked context, acquire the task's rq lock, * so that we can safely access p->cpus_ptr and p->nr_cpus_allowed. * * Otherwise, allow to use this kfunc only from ops.select_cpu() * and ops.select_enqueue().
*/ if (scx_kf_allowed_if_unlocked()) {
rq = task_rq_lock(p, &rf);
} else { if (!scx_kf_allowed(SCX_KF_SELECT_CPU | SCX_KF_ENQUEUE)) return -EPERM;
rq = scx_locked_rq();
}
/* * Validate locking correctness to access p->cpus_ptr and * p->nr_cpus_allowed: if we're holding an rq lock, we're safe; * otherwise, assert that p->pi_lock is held.
*/ if (!rq)
lockdep_assert_held(&p->pi_lock);
/* * This may also be called from ops.enqueue(), so we need to handle * per-CPU tasks as well. For these tasks, we can skip all idle CPU * selection optimizations and simply check whether the previously * used CPU is idle and within the allowed cpumask.
*/ if (p->nr_cpus_allowed == 1 || is_bpf_migration_disabled(p)) { if (cpumask_test_cpu(prev_cpu, allowed ?: p->cpus_ptr) &&
scx_idle_test_and_clear_cpu(prev_cpu))
cpu = prev_cpu; else
cpu = -EBUSY;
} else {
cpu = scx_select_cpu_dfl(p, prev_cpu, wake_flags,
allowed ?: p->cpus_ptr, flags);
}
if (scx_kf_allowed_if_unlocked())
task_rq_unlock(rq, p, &rf);
return cpu;
}
/** * 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)
{ if (!kf_cpu_valid(cpu, NULL)) return NUMA_NO_NODE;
return cpu_to_node(cpu);
}
/** * scx_bpf_select_cpu_dfl - The default implementation of ops.select_cpu() * @p: task_struct to select a CPU for * @prev_cpu: CPU @p was on previously * @wake_flags: %SCX_WAKE_* flags * @is_idle: out parameter indicating whether the returned CPU is idle * * Can be called from ops.select_cpu(), ops.enqueue(), or from an unlocked * context such as a BPF test_run() call, as long as built-in CPU selection * is enabled: ops.update_idle() is missing or %SCX_OPS_KEEP_BUILTIN_IDLE * is set. * * Returns the picked CPU with *@is_idle indicating whether the picked CPU is * currently idle and thus a good candidate for direct dispatching.
*/
__bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
u64 wake_flags, bool *is_idle)
{
s32 cpu;
/** * scx_bpf_select_cpu_and - Pick an idle CPU usable by task @p, * prioritizing those in @cpus_allowed * @p: task_struct to select a CPU for * @prev_cpu: CPU @p was on previously * @wake_flags: %SCX_WAKE_* flags * @cpus_allowed: cpumask of allowed CPUs * @flags: %SCX_PICK_IDLE* flags * * Can be called from ops.select_cpu(), ops.enqueue(), or from an unlocked * context such as a BPF test_run() call, as long as built-in CPU selection * is enabled: ops.update_idle() is missing or %SCX_OPS_KEEP_BUILTIN_IDLE * is set. * * @p, @prev_cpu and @wake_flags match ops.select_cpu(). * * Returns the selected idle CPU, which will be automatically awakened upon * returning from ops.select_cpu() and can be used for direct dispatch, or * a negative value if no idle CPU is available.
*/
__bpf_kfunc s32 scx_bpf_select_cpu_and(struct task_struct *p, s32 prev_cpu, u64 wake_flags, conststruct cpumask *cpus_allowed, u64 flags)
{ return select_cpu_from_kfunc(p, prev_cpu, wake_flags, cpus_allowed, flags);
}
/** * scx_bpf_get_idle_cpumask_node - Get a referenced kptr to the * idle-tracking per-CPU cpumask of a target NUMA node. * @node: 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_error().
*/
__bpf_kfunc conststruct cpumask *scx_bpf_get_idle_cpumask_node(int node)
{
node = validate_node(node); if (node < 0) return cpu_none_mask;
return idle_cpumask(node)->cpu;
}
/** * scx_bpf_get_idle_cpumask - Get a referenced kptr to the idle-tracking * per-CPU cpumask. * * Returns an empty mask if idle tracking is not enabled, or running on a * UP kernel.
*/
__bpf_kfunc conststruct cpumask *scx_bpf_get_idle_cpumask(void)
{ if (static_branch_unlikely(&scx_builtin_idle_per_node)) {
scx_kf_error("SCX_OPS_BUILTIN_IDLE_PER_NODE enabled"); return cpu_none_mask;
}
if (!check_builtin_idle_enabled()) return cpu_none_mask;
return idle_cpumask(NUMA_NO_NODE)->cpu;
}
/** * 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. * @node: 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_error().
*/
__bpf_kfunc conststruct cpumask *scx_bpf_get_idle_smtmask_node(int node)
{
node = validate_node(node); if (node < 0) return cpu_none_mask;
if (sched_smt_active()) return idle_cpumask(node)->smt; else return idle_cpumask(node)->cpu;
}
/** * 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 * core is free. * * Returns an empty mask if idle tracking is not enabled, or running on a * UP kernel.
*/
__bpf_kfunc conststruct cpumask *scx_bpf_get_idle_smtmask(void)
{ if (static_branch_unlikely(&scx_builtin_idle_per_node)) {
scx_kf_error("SCX_OPS_BUILTIN_IDLE_PER_NODE enabled"); return cpu_none_mask;
}
if (!check_builtin_idle_enabled()) return cpu_none_mask;
if (sched_smt_active()) return idle_cpumask(NUMA_NO_NODE)->smt; else return idle_cpumask(NUMA_NO_NODE)->cpu;
}
/** * scx_bpf_put_idle_cpumask - Release a previously acquired referenced kptr to * either the percpu, or SMT idle-tracking cpumask. * @idle_mask: &cpumask to use
*/
__bpf_kfunc void scx_bpf_put_idle_cpumask(conststruct cpumask *idle_mask)
{ /* * Empty function body because we aren't actually acquiring or releasing * a reference to a global idle cpumask, which is read-only in the * caller and is never released. The acquire / release semantics here * are just used to make the cpumask a trusted pointer in the caller.
*/
}
/** * scx_bpf_test_and_clear_cpu_idle - Test and clear @cpu's idle state * @cpu: cpu to test and clear idle for * * Returns %true if @cpu was idle and its idle state was successfully cleared. * %false otherwise. * * Unavailable if ops.update_idle() is implemented and * %SCX_OPS_KEEP_BUILTIN_IDLE is not set.
*/
__bpf_kfunc bool scx_bpf_test_and_clear_cpu_idle(s32 cpu)
{ if (!check_builtin_idle_enabled()) returnfalse;
if (!kf_cpu_valid(cpu, NULL)) returnfalse;
return scx_idle_test_and_clear_cpu(cpu);
}
/** * scx_bpf_pick_idle_cpu_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_node(conststruct cpumask *cpus_allowed, int node, u64 flags)
{
node = validate_node(node); if (node < 0) return node;
/** * scx_bpf_pick_idle_cpu - Pick and claim an idle cpu * @cpus_allowed: Allowed cpumask * @flags: %SCX_PICK_IDLE_CPU_* flags * * Pick and claim an idle cpu in @cpus_allowed. Returns the picked idle cpu * number on success. -%EBUSY if no matching cpu was found. * * Idle CPU tracking may race against CPU scheduling state transitions. For * example, this function may return -%EBUSY as CPUs are transitioning into the * idle state. If the caller then assumes that there will be dispatch events on * the CPUs as they were all busy, the scheduler may end up stalling with CPUs * idling while there are pending tasks. Use scx_bpf_pick_any_cpu() and * scx_bpf_kick_cpu() to guarantee that there will be at least one dispatch * event in the near future. * * 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_node() instead.
*/
__bpf_kfunc s32 scx_bpf_pick_idle_cpu(conststruct cpumask *cpus_allowed,
u64 flags)
{ if (static_branch_maybe(CONFIG_NUMA, &scx_builtin_idle_per_node)) {
scx_kf_error("per-node idle tracking is enabled"); return -EBUSY;
}
/** * scx_bpf_pick_any_cpu_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, regardless of * the CPU idle state). * * 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_node(conststruct 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;
if (flags & SCX_PICK_IDLE_IN_NODE)
cpu = cpumask_any_and_distribute(cpumask_of_node(node), cpus_allowed); else
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 * @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. * * 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_node() instead.
*/
__bpf_kfunc s32 scx_bpf_pick_any_cpu(conststruct cpumask *cpus_allowed,
u64 flags)
{
s32 cpu;
if (static_branch_maybe(CONFIG_NUMA, &scx_builtin_idle_per_node)) {
scx_kf_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) return cpu;
}
cpu = cpumask_any_distribute(cpus_allowed); if (cpu < nr_cpu_ids) return cpu; else return -EBUSY;
}
ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &scx_kfunc_set_idle) ||
register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &scx_kfunc_set_idle) ||
register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &scx_kfunc_set_idle);
return ret;
}
Messung V0.5
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Die Informationen auf dieser Webseite wurden
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Bemerkung:
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