From cdf5a6faa8cf0ef62ec238a18b898ca9827bc472 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 29 Apr 2025 08:40:10 -1000 Subject: [PATCH] sched_ext: Move dsq_hash into scx_sched User DSQs are going to become per scheduler instance. Move dsq_hash into scx_sched. This shifts the code that assumes scx_root to be the only scx_sched instance up the call stack but doesn't remove them yet. v2: Add missing rcu_read_lock() in scx_bpf_destroy_dsq() as per Andrea. Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi Acked-by: Changwoo Min --- kernel/sched/ext.c | 122 ++++++++++++++++++++++++++++++--------------- 1 file changed, 82 insertions(+), 40 deletions(-) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 91b89cff52bf..62ec2d1b195e 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -770,6 +770,7 @@ struct scx_sched { struct sched_ext_ops ops; DECLARE_BITMAP(has_op, SCX_OPI_END); + struct rhashtable dsq_hash; bool warned_zero_slice; atomic_t exit_kind; @@ -1016,7 +1017,6 @@ static const struct rhashtable_params dsq_hash_params = { .head_offset = offsetof(struct scx_dispatch_q, hash_node), }; -static struct rhashtable dsq_hash; static LLIST_HEAD(dsqs_to_free); /* dispatch buf */ @@ -1114,9 +1114,9 @@ static struct scx_dispatch_q *find_global_dsq(struct task_struct *p) return global_dsqs[cpu_to_node(task_cpu(p))]; } -static struct scx_dispatch_q *find_user_dsq(u64 dsq_id) +static struct scx_dispatch_q *find_user_dsq(struct scx_sched *sch, u64 dsq_id) { - return rhashtable_lookup_fast(&dsq_hash, &dsq_id, dsq_hash_params); + return rhashtable_lookup_fast(&sch->dsq_hash, &dsq_id, dsq_hash_params); } /* @@ -2059,7 +2059,8 @@ static void dispatch_dequeue(struct rq *rq, struct task_struct *p) raw_spin_unlock(&dsq->lock); } -static struct scx_dispatch_q *find_dsq_for_dispatch(struct rq *rq, u64 dsq_id, +static struct scx_dispatch_q *find_dsq_for_dispatch(struct scx_sched *sch, + struct rq *rq, u64 dsq_id, struct task_struct *p) { struct scx_dispatch_q *dsq; @@ -2079,7 +2080,7 @@ static struct scx_dispatch_q *find_dsq_for_dispatch(struct rq *rq, u64 dsq_id, if (dsq_id == SCX_DSQ_GLOBAL) dsq = find_global_dsq(p); else - dsq = find_user_dsq(dsq_id); + dsq = find_user_dsq(sch, dsq_id); if (unlikely(!dsq)) { scx_error("non-existent DSQ 0x%llx for %s[%d]", @@ -2120,11 +2121,12 @@ static void mark_direct_dispatch(struct task_struct *ddsp_task, p->scx.ddsp_enq_flags = enq_flags; } -static void direct_dispatch(struct task_struct *p, u64 enq_flags) +static void direct_dispatch(struct scx_sched *sch, struct task_struct *p, + u64 enq_flags) { struct rq *rq = task_rq(p); struct scx_dispatch_q *dsq = - find_dsq_for_dispatch(rq, p->scx.ddsp_dsq_id, p); + find_dsq_for_dispatch(sch, rq, p->scx.ddsp_dsq_id, p); touch_core_sched_dispatch(rq, p); @@ -2183,6 +2185,7 @@ static bool scx_rq_online(struct rq *rq) static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags, int sticky_cpu) { + struct scx_sched *sch = scx_root; struct task_struct **ddsp_taskp; unsigned long qseq; @@ -2249,7 +2252,7 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags, return; direct: - direct_dispatch(p, enq_flags); + direct_dispatch(sch, p, enq_flags); return; local: @@ -2909,7 +2912,8 @@ static void dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_dsq, * was valid in the first place. Make sure that the task is still owned by the * BPF scheduler and claim the ownership before dispatching. */ -static void finish_dispatch(struct rq *rq, struct task_struct *p, +static void finish_dispatch(struct scx_sched *sch, struct rq *rq, + struct task_struct *p, unsigned long qseq_at_dispatch, u64 dsq_id, u64 enq_flags) { @@ -2962,7 +2966,7 @@ retry: BUG_ON(!(p->scx.flags & SCX_TASK_QUEUED)); - dsq = find_dsq_for_dispatch(this_rq(), dsq_id, p); + dsq = find_dsq_for_dispatch(sch, this_rq(), dsq_id, p); if (dsq->id == SCX_DSQ_LOCAL) dispatch_to_local_dsq(rq, dsq, p, enq_flags); @@ -2970,7 +2974,7 @@ retry: dispatch_enqueue(dsq, p, enq_flags | SCX_ENQ_CLEAR_OPSS); } -static void flush_dispatch_buf(struct rq *rq) +static void flush_dispatch_buf(struct scx_sched *sch, struct rq *rq) { struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx); u32 u; @@ -2978,7 +2982,7 @@ static void flush_dispatch_buf(struct rq *rq) for (u = 0; u < dspc->cursor; u++) { struct scx_dsp_buf_ent *ent = &dspc->buf[u]; - finish_dispatch(rq, ent->task, ent->qseq, ent->dsq_id, + finish_dispatch(sch, rq, ent->task, ent->qseq, ent->dsq_id, ent->enq_flags); } @@ -2988,6 +2992,7 @@ static void flush_dispatch_buf(struct rq *rq) static int balance_one(struct rq *rq, struct task_struct *prev) { + struct scx_sched *sch = scx_root; struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx); bool prev_on_scx = prev->sched_class == &ext_sched_class; bool prev_on_rq = prev->scx.flags & SCX_TASK_QUEUED; @@ -3055,7 +3060,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev) SCX_CALL_OP(SCX_KF_DISPATCH, dispatch, rq, cpu_of(rq), prev_on_scx ? prev : NULL); - flush_dispatch_buf(rq); + flush_dispatch_buf(sch, rq); if (prev_on_rq && prev->scx.slice) { rq->scx.flags |= SCX_RQ_BAL_KEEP; @@ -3149,11 +3154,12 @@ static void process_ddsp_deferred_locals(struct rq *rq) */ while ((p = list_first_entry_or_null(&rq->scx.ddsp_deferred_locals, struct task_struct, scx.dsq_list.node))) { + struct scx_sched *sch = scx_root; struct scx_dispatch_q *dsq; list_del_init(&p->scx.dsq_list.node); - dsq = find_dsq_for_dispatch(rq, p->scx.ddsp_dsq_id, p); + dsq = find_dsq_for_dispatch(sch, rq, p->scx.ddsp_dsq_id, p); if (!WARN_ON_ONCE(dsq->id != SCX_DSQ_LOCAL)) dispatch_to_local_dsq(rq, dsq, p, p->scx.ddsp_enq_flags); } @@ -4207,14 +4213,14 @@ static void free_dsq_irq_workfn(struct irq_work *irq_work) static DEFINE_IRQ_WORK(free_dsq_irq_work, free_dsq_irq_workfn); -static void destroy_dsq(u64 dsq_id) +static void destroy_dsq(struct scx_sched *sch, u64 dsq_id) { struct scx_dispatch_q *dsq; unsigned long flags; rcu_read_lock(); - dsq = find_user_dsq(dsq_id); + dsq = find_user_dsq(sch, dsq_id); if (!dsq) goto out_unlock_rcu; @@ -4226,7 +4232,8 @@ static void destroy_dsq(u64 dsq_id) goto out_unlock_dsq; } - if (rhashtable_remove_fast(&dsq_hash, &dsq->hash_node, dsq_hash_params)) + if (rhashtable_remove_fast(&sch->dsq_hash, &dsq->hash_node, + dsq_hash_params)) goto out_unlock_dsq; /* @@ -4400,7 +4407,21 @@ static void scx_sched_free_rcu_work(struct work_struct *work) { struct rcu_work *rcu_work = to_rcu_work(work); struct scx_sched *sch = container_of(rcu_work, struct scx_sched, rcu_work); + struct rhashtable_iter rht_iter; + struct scx_dispatch_q *dsq; + + rhashtable_walk_enter(&sch->dsq_hash, &rht_iter); + do { + rhashtable_walk_start(&rht_iter); + + while ((dsq = rhashtable_walk_next(&rht_iter)) && !IS_ERR(dsq)) + destroy_dsq(sch, dsq->id); + + rhashtable_walk_stop(&rht_iter); + } while (dsq == ERR_PTR(-EAGAIN)); + rhashtable_walk_exit(&rht_iter); + rhashtable_free_and_destroy(&sch->dsq_hash, NULL, NULL); free_exit_info(sch->exit_info); kfree(sch); } @@ -4704,8 +4725,6 @@ static void scx_disable_workfn(struct kthread_work *work) struct scx_exit_info *ei = sch->exit_info; struct scx_task_iter sti; struct task_struct *p; - struct rhashtable_iter rht_iter; - struct scx_dispatch_q *dsq; int kind, cpu; kind = atomic_read(&sch->exit_kind); @@ -4837,17 +4856,6 @@ static void scx_disable_workfn(struct kthread_work *work) */ kobject_del(&sch->kobj); - rhashtable_walk_enter(&dsq_hash, &rht_iter); - do { - rhashtable_walk_start(&rht_iter); - - while ((dsq = rhashtable_walk_next(&rht_iter)) && !IS_ERR(dsq)) - destroy_dsq(dsq->id); - - rhashtable_walk_stop(&rht_iter); - } while (dsq == ERR_PTR(-EAGAIN)); - rhashtable_walk_exit(&rht_iter); - free_percpu(scx_dsp_ctx); scx_dsp_ctx = NULL; scx_dsp_max_batch = 0; @@ -5251,6 +5259,10 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops) goto err_free_sch; } + ret = rhashtable_init(&sch->dsq_hash, &dsq_hash_params); + if (ret < 0) + goto err_free_ei; + atomic_set(&sch->exit_kind, SCX_EXIT_NONE); sch->ops = *ops; ops->priv = sch; @@ -5258,10 +5270,12 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops) sch->kobj.kset = scx_kset; ret = kobject_init_and_add(&sch->kobj, &scx_ktype, NULL, "root"); if (ret < 0) - goto err_free_ei; + goto err_free_hash; return sch; +err_free_hash: + rhashtable_free_and_destroy(&sch->dsq_hash, NULL, NULL); err_free_ei: free_exit_info(sch->exit_info); err_free_sch: @@ -6102,7 +6116,6 @@ void __init init_sched_ext_class(void) WRITE_ONCE(v, SCX_ENQ_WAKEUP | SCX_DEQ_SLEEP | SCX_KICK_PREEMPT | SCX_TG_ONLINE); - BUG_ON(rhashtable_init(&dsq_hash, &dsq_hash_params)); scx_idle_init_masks(); scx_kick_cpus_pnt_seqs = @@ -6303,6 +6316,7 @@ static const struct btf_kfunc_id_set scx_kfunc_set_enqueue_dispatch = { static bool scx_dsq_move(struct bpf_iter_scx_dsq_kern *kit, struct task_struct *p, u64 dsq_id, u64 enq_flags) { + struct scx_sched *sch = scx_root; struct scx_dispatch_q *src_dsq = kit->dsq, *dst_dsq; struct rq *this_rq, *src_rq, *locked_rq; bool dispatched = false; @@ -6355,7 +6369,7 @@ static bool scx_dsq_move(struct bpf_iter_scx_dsq_kern *kit, } /* @p is still on $src_dsq and stable, determine the destination */ - dst_dsq = find_dsq_for_dispatch(this_rq, dsq_id, p); + dst_dsq = find_dsq_for_dispatch(sch, this_rq, dsq_id, p); /* * Apply vtime and slice updates before moving so that the new time is @@ -6435,15 +6449,16 @@ __bpf_kfunc void scx_bpf_dispatch_cancel(void) */ __bpf_kfunc bool scx_bpf_dsq_move_to_local(u64 dsq_id) { + struct scx_sched *sch = scx_root; struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx); struct scx_dispatch_q *dsq; if (!scx_kf_allowed(SCX_KF_DISPATCH)) return false; - flush_dispatch_buf(dspc->rq); + flush_dispatch_buf(sch, dspc->rq); - dsq = find_user_dsq(dsq_id); + dsq = find_user_dsq(sch, dsq_id); if (unlikely(!dsq)) { scx_error("invalid DSQ ID 0x%016llx", dsq_id); return false; @@ -6704,6 +6719,7 @@ __bpf_kfunc_start_defs(); __bpf_kfunc s32 scx_bpf_create_dsq(u64 dsq_id, s32 node) { struct scx_dispatch_q *dsq; + struct scx_sched *sch; s32 ret; if (unlikely(node >= (int)nr_node_ids || @@ -6719,8 +6735,16 @@ __bpf_kfunc s32 scx_bpf_create_dsq(u64 dsq_id, s32 node) init_dsq(dsq, dsq_id); - ret = rhashtable_lookup_insert_fast(&dsq_hash, &dsq->hash_node, - dsq_hash_params); + rcu_read_lock(); + + sch = rcu_dereference(scx_root); + if (sch) + ret = rhashtable_lookup_insert_fast(&sch->dsq_hash, &dsq->hash_node, + dsq_hash_params); + else + ret = -ENODEV; + + rcu_read_unlock(); if (ret) kfree(dsq); return ret; @@ -6819,11 +6843,18 @@ out: */ __bpf_kfunc s32 scx_bpf_dsq_nr_queued(u64 dsq_id) { + struct scx_sched *sch; struct scx_dispatch_q *dsq; s32 ret; preempt_disable(); + sch = rcu_dereference_sched(scx_root); + if (!sch) { + ret = -ENODEV; + goto out; + } + if (dsq_id == SCX_DSQ_LOCAL) { ret = READ_ONCE(this_rq()->scx.local_dsq.nr); goto out; @@ -6835,7 +6866,7 @@ __bpf_kfunc s32 scx_bpf_dsq_nr_queued(u64 dsq_id) goto out; } } else { - dsq = find_user_dsq(dsq_id); + dsq = find_user_dsq(sch, dsq_id); if (dsq) { ret = READ_ONCE(dsq->nr); goto out; @@ -6858,7 +6889,13 @@ out: */ __bpf_kfunc void scx_bpf_destroy_dsq(u64 dsq_id) { - destroy_dsq(dsq_id); + struct scx_sched *sch; + + rcu_read_lock(); + sch = rcu_dereference(scx_root); + if (sch) + destroy_dsq(sch, dsq_id); + rcu_read_unlock(); } /** @@ -6875,16 +6912,21 @@ __bpf_kfunc int bpf_iter_scx_dsq_new(struct bpf_iter_scx_dsq *it, u64 dsq_id, u64 flags) { struct bpf_iter_scx_dsq_kern *kit = (void *)it; + struct scx_sched *sch; BUILD_BUG_ON(sizeof(struct bpf_iter_scx_dsq_kern) > sizeof(struct bpf_iter_scx_dsq)); BUILD_BUG_ON(__alignof__(struct bpf_iter_scx_dsq_kern) != __alignof__(struct bpf_iter_scx_dsq)); + sch = rcu_dereference(scx_root); + if (!sch) + return -ENODEV; + if (flags & ~__SCX_DSQ_ITER_USER_FLAGS) return -EINVAL; - kit->dsq = find_user_dsq(dsq_id); + kit->dsq = find_user_dsq(sch, dsq_id); if (!kit->dsq) return -ENOENT; -- 2.50.1