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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1755536552; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/YrYUzXccRuZ9yFhf36EzBvX3yiPzvgrHin8+im7U8c=; b=ZJ0SHZLmHc8edLK5ZYYB4wbYZfDWJcfd2/Tf3z0l1o5HxRXQSbxTpe09chOrUd8ci7phP+ ieVgN4zISNFQN8Jh/sSklBbnBlw8SL9MLoPvSYkPnbGeNrLInaafU8anGtjdp58uCaIjxx xCRExOHuT7oMdQG9t4IXTVWnQQul9mE= From: Roman Gushchin To: linux-mm@kvack.org, bpf@vger.kernel.org Cc: Suren Baghdasaryan , Johannes Weiner , Michal Hocko , David Rientjes , Matt Bobrowski , Song Liu , Kumar Kartikeya Dwivedi , Alexei Starovoitov , Andrew Morton , linux-kernel@vger.kernel.org, Roman Gushchin Subject: [PATCH v1 12/14] sched: psi: implement psi trigger handling using bpf Date: Mon, 18 Aug 2025 10:01:34 -0700 Message-ID: <20250818170136.209169-13-roman.gushchin@linux.dev> In-Reply-To: <20250818170136.209169-1-roman.gushchin@linux.dev> References: <20250818170136.209169-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: b7rrdk9r6brt64o7phf5156fse9fcp1y X-Rspam-User: X-Rspamd-Queue-Id: 0B998100007 X-Rspamd-Server: rspam01 X-HE-Tag: 1755536553-660787 X-HE-Meta: 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 cnHVK2KG UDfS+DSEmLtShoT5cGxWdZwb+8oJVyaEJEHRYrcxDECutxVsurVvS1gNEqj1v2U4YJCL/1j4JGEz/OQxQQHOSK4xEwu7c/RdYd+VeiRB0rL1UMLlyL4za4cL25G9DSpgLxTGImx9KyXqYr0K7AGB2o3Booyv9S/zzW69IHrlT4qp2SDI+QVM1z8v1EsmWW/BuMuLJJWnxeMrpXyxtif6jP4V+gaT45I+T/qXnQI8cdnj6qOo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This patch implements a bpf struct ops-based mechanism to create psi triggers, attach them to cgroups or system wide and handle psi events in bpf. The struct ops provides 3 callbacks: - init() called once at load, handy for creating psi triggers - handle_psi_event() called every time a psi trigger fires - handle_cgroup_free() called if a cgroup with an attached trigger is being freed A single struct ops can create a number of psi triggers, both cgroup-scoped and system-wide. All 3 struct ops callbacks can be sleepable. handle_psi_event() handlers are executed using a separate workqueue, so it won't affect the latency of other psi triggers. Signed-off-by: Roman Gushchin --- include/linux/bpf_psi.h | 71 ++++++++++ include/linux/psi_types.h | 43 +++++- kernel/sched/bpf_psi.c | 253 +++++++++++++++++++++++++++++++++++ kernel/sched/build_utility.c | 4 + kernel/sched/psi.c | 49 +++++-- 5 files changed, 408 insertions(+), 12 deletions(-) create mode 100644 include/linux/bpf_psi.h create mode 100644 kernel/sched/bpf_psi.c diff --git a/include/linux/bpf_psi.h b/include/linux/bpf_psi.h new file mode 100644 index 000000000000..826ab89ac11c --- /dev/null +++ b/include/linux/bpf_psi.h @@ -0,0 +1,71 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ + +#ifndef __BPF_PSI_H +#define __BPF_PSI_H + +#include +#include +#include +#include + +struct cgroup; +struct bpf_psi; +struct psi_trigger; +struct psi_trigger_params; + +#define BPF_PSI_FULL 0x80000000 + +struct bpf_psi_ops { + /** + * @init: Initialization callback, suited for creating psi triggers. + * @bpf_psi: bpf_psi pointer, can be passed to bpf_psi_create_trigger(). + * + * A non-0 return value means the initialization has been failed. + */ + int (*init)(struct bpf_psi *bpf_psi); + + /** + * @handle_psi_event: PSI event callback + * @t: psi_trigger pointer + */ + void (*handle_psi_event)(struct psi_trigger *t); + + /** + * @handle_cgroup_free: Cgroup free callback + * @cgroup_id: Id of freed cgroup + * + * Called every time a cgroup with an attached bpf psi trigger is freed. + * No psi events can be raised after handle_cgroup_free(). + */ + void (*handle_cgroup_free)(u64 cgroup_id); + + /* private */ + struct bpf_psi *bpf_psi; +}; + +struct bpf_psi { + spinlock_t lock; + struct list_head triggers; + struct bpf_psi_ops *ops; + struct srcu_struct srcu; +}; + +#ifdef CONFIG_BPF_SYSCALL +void bpf_psi_add_trigger(struct psi_trigger *t, + const struct psi_trigger_params *params); +void bpf_psi_remove_trigger(struct psi_trigger *t); +void bpf_psi_handle_event(struct psi_trigger *t); +#ifdef CONFIG_CGROUPS +void bpf_psi_cgroup_free(struct cgroup *cgroup); +#endif + +#else /* CONFIG_BPF_SYSCALL */ +static inline void bpf_psi_add_trigger(struct psi_trigger *t, + const struct psi_trigger_params *params) {} +static inline void bpf_psi_remove_trigger(struct psi_trigger *t) {} +static inline void bpf_psi_handle_event(struct psi_trigger *t) {} +static inline void bpf_psi_cgroup_free(struct cgroup *cgroup) {} + +#endif /* CONFIG_BPF_SYSCALL */ + +#endif /* __BPF_PSI_H */ diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h index cea54121d9b9..f695cc34cfd4 100644 --- a/include/linux/psi_types.h +++ b/include/linux/psi_types.h @@ -124,6 +124,7 @@ struct psi_window { enum psi_trigger_type { PSI_SYSTEM, PSI_CGROUP, + PSI_BPF, }; struct psi_trigger_params { @@ -145,8 +146,15 @@ struct psi_trigger_params { /* Privileged triggers are treated differently */ bool privileged; - /* Link to kernfs open file, only for PSI_CGROUP */ - struct kernfs_open_file *of; + union { + /* Link to kernfs open file, only for PSI_CGROUP */ + struct kernfs_open_file *of; + +#ifdef CONFIG_BPF_SYSCALL + /* Link to bpf_psi structure, only for BPF_PSI */ + struct bpf_psi *bpf_psi; +#endif + }; }; struct psi_trigger { @@ -188,6 +196,31 @@ struct psi_trigger { /* Trigger type - PSI_AVGS for unprivileged, PSI_POLL for RT */ enum psi_aggregators aggregator; + +#ifdef CONFIG_BPF_SYSCALL + /* Fields specific to PSI_BPF triggers */ + + /* Bpf psi structure for events handling */ + struct bpf_psi *bpf_psi; + + /* List node inside bpf_psi->triggers list */ + struct list_head bpf_psi_node; + + /* List node inside group->bpf_triggers list */ + struct list_head bpf_group_node; + + /* Work structure, used to execute event handlers */ + struct work_struct bpf_work; + + /* + * Whether the trigger is being pinned in memory. + * Protected by group->bpf_triggers_lock. + */ + bool pinned; + + /* Cgroup Id */ + u64 cgroup_id; +#endif }; struct psi_group { @@ -236,6 +269,12 @@ struct psi_group { u64 rtpoll_total[NR_PSI_STATES - 1]; u64 rtpoll_next_update; u64 rtpoll_until; + +#ifdef CONFIG_BPF_SYSCALL + /* List of triggers owned by bpf and corresponding lock */ + spinlock_t bpf_triggers_lock; + struct list_head bpf_triggers; +#endif }; #else /* CONFIG_PSI */ diff --git a/kernel/sched/bpf_psi.c b/kernel/sched/bpf_psi.c new file mode 100644 index 000000000000..2ea9d7276b21 --- /dev/null +++ b/kernel/sched/bpf_psi.c @@ -0,0 +1,253 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * BPF PSI event handlers + * + * Author: Roman Gushchin + */ + +#include +#include + +static struct workqueue_struct *bpf_psi_wq; + +static struct bpf_psi *bpf_psi_create(struct bpf_psi_ops *ops) +{ + struct bpf_psi *bpf_psi; + + bpf_psi = kzalloc(sizeof(*bpf_psi), GFP_KERNEL); + if (!bpf_psi) + return NULL; + + if (init_srcu_struct(&bpf_psi->srcu)) { + kfree(bpf_psi); + return NULL; + } + + spin_lock_init(&bpf_psi->lock); + bpf_psi->ops = ops; + INIT_LIST_HEAD(&bpf_psi->triggers); + ops->bpf_psi = bpf_psi; + + return bpf_psi; +} + +static void bpf_psi_free(struct bpf_psi *bpf_psi) +{ + cleanup_srcu_struct(&bpf_psi->srcu); + kfree(bpf_psi); +} + +static void bpf_psi_handle_event_fn(struct work_struct *work) +{ + struct psi_trigger *t; + struct bpf_psi *bpf_psi; + int idx; + + t = container_of(work, struct psi_trigger, bpf_work); + bpf_psi = READ_ONCE(t->bpf_psi); + + if (likely(bpf_psi)) { + idx = srcu_read_lock(&bpf_psi->srcu); + if (bpf_psi->ops->handle_psi_event) + bpf_psi->ops->handle_psi_event(t); + srcu_read_unlock(&bpf_psi->srcu, idx); + } +} + +void bpf_psi_add_trigger(struct psi_trigger *t, + const struct psi_trigger_params *params) +{ + t->bpf_psi = params->bpf_psi; + t->pinned = false; + INIT_WORK(&t->bpf_work, bpf_psi_handle_event_fn); + + spin_lock(&t->bpf_psi->lock); + list_add(&t->bpf_psi_node, &t->bpf_psi->triggers); + spin_unlock(&t->bpf_psi->lock); + + spin_lock(&t->group->bpf_triggers_lock); + list_add(&t->bpf_group_node, &t->group->bpf_triggers); + spin_unlock(&t->group->bpf_triggers_lock); +} + +void bpf_psi_remove_trigger(struct psi_trigger *t) +{ + spin_lock(&t->group->bpf_triggers_lock); + list_del(&t->bpf_group_node); + spin_unlock(&t->group->bpf_triggers_lock); + + spin_lock(&t->bpf_psi->lock); + list_del(&t->bpf_psi_node); + spin_unlock(&t->bpf_psi->lock); +} + +#ifdef CONFIG_CGROUPS +void bpf_psi_cgroup_free(struct cgroup *cgroup) +{ + struct psi_group *group = cgroup->psi; + u64 cgrp_id = cgroup_id(cgroup); + struct psi_trigger *t, *p; + struct bpf_psi *bpf_psi; + LIST_HEAD(to_destroy); + int idx; + + spin_lock(&group->bpf_triggers_lock); + list_for_each_entry_safe(t, p, &group->bpf_triggers, bpf_group_node) { + if (!t->pinned) { + t->pinned = true; + list_move(&t->bpf_group_node, &to_destroy); + } + } + spin_unlock(&group->bpf_triggers_lock); + + list_for_each_entry_safe(t, p, &to_destroy, bpf_group_node) { + bpf_psi = READ_ONCE(t->bpf_psi); + + idx = srcu_read_lock(&bpf_psi->srcu); + if (bpf_psi->ops->handle_cgroup_free) + bpf_psi->ops->handle_cgroup_free(cgrp_id); + srcu_read_unlock(&bpf_psi->srcu, idx); + + spin_lock(&bpf_psi->lock); + list_del(&t->bpf_psi_node); + spin_unlock(&bpf_psi->lock); + + WRITE_ONCE(t->bpf_psi, NULL); + flush_workqueue(bpf_psi_wq); + synchronize_srcu(&bpf_psi->srcu); + psi_trigger_destroy(t); + } +} +#endif + +void bpf_psi_handle_event(struct psi_trigger *t) +{ + queue_work(bpf_psi_wq, &t->bpf_work); +} + +// bpf struct ops + +static int __bpf_psi_init(struct bpf_psi *bpf_psi) { return 0; } +static void __bpf_psi_handle_psi_event(struct psi_trigger *t) {} +static void __bpf_psi_handle_cgroup_free(u64 cgroup_id) {} + +static struct bpf_psi_ops __bpf_psi_ops = { + .init = __bpf_psi_init, + .handle_psi_event = __bpf_psi_handle_psi_event, + .handle_cgroup_free = __bpf_psi_handle_cgroup_free, +}; + +static const struct bpf_func_proto * +bpf_psi_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) +{ + return tracing_prog_func_proto(func_id, prog); +} + +static bool bpf_psi_ops_is_valid_access(int off, int size, + enum bpf_access_type type, + const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + return bpf_tracing_btf_ctx_access(off, size, type, prog, info); +} + +static const struct bpf_verifier_ops bpf_psi_verifier_ops = { + .get_func_proto = bpf_psi_func_proto, + .is_valid_access = bpf_psi_ops_is_valid_access, +}; + +static int bpf_psi_ops_reg(void *kdata, struct bpf_link *link) +{ + struct bpf_psi_ops *ops = kdata; + struct bpf_psi *bpf_psi; + + bpf_psi = bpf_psi_create(ops); + if (!bpf_psi) + return -ENOMEM; + + return ops->init(bpf_psi); +} + +static void bpf_psi_ops_unreg(void *kdata, struct bpf_link *link) +{ + struct bpf_psi_ops *ops = kdata; + struct bpf_psi *bpf_psi = ops->bpf_psi; + struct psi_trigger *t, *p; + LIST_HEAD(to_destroy); + + spin_lock(&bpf_psi->lock); + list_for_each_entry_safe(t, p, &bpf_psi->triggers, bpf_psi_node) { + spin_lock(&t->group->bpf_triggers_lock); + if (!t->pinned) { + t->pinned = true; + list_move(&t->bpf_group_node, &to_destroy); + list_del(&t->bpf_psi_node); + + WRITE_ONCE(t->bpf_psi, NULL); + } + spin_unlock(&t->group->bpf_triggers_lock); + } + spin_unlock(&bpf_psi->lock); + + flush_workqueue(bpf_psi_wq); + synchronize_srcu(&bpf_psi->srcu); + + list_for_each_entry_safe(t, p, &to_destroy, bpf_group_node) + psi_trigger_destroy(t); + + bpf_psi_free(bpf_psi); +} + +static int bpf_psi_ops_check_member(const struct btf_type *t, + const struct btf_member *member, + const struct bpf_prog *prog) +{ + return 0; +} + +static int bpf_psi_ops_init_member(const struct btf_type *t, + const struct btf_member *member, + void *kdata, const void *udata) +{ + return 0; +} + +static int bpf_psi_ops_init(struct btf *btf) +{ + return 0; +} + +static struct bpf_struct_ops bpf_psi_bpf_ops = { + .verifier_ops = &bpf_psi_verifier_ops, + .reg = bpf_psi_ops_reg, + .unreg = bpf_psi_ops_unreg, + .check_member = bpf_psi_ops_check_member, + .init_member = bpf_psi_ops_init_member, + .init = bpf_psi_ops_init, + .name = "bpf_psi_ops", + .owner = THIS_MODULE, + .cfi_stubs = &__bpf_psi_ops +}; + +static int __init bpf_psi_struct_ops_init(void) +{ + int wq_flags = WQ_MEM_RECLAIM | WQ_UNBOUND | WQ_HIGHPRI; + int err; + + bpf_psi_wq = alloc_workqueue("bpf_psi_wq", wq_flags, 0); + if (!bpf_psi_wq) + return -ENOMEM; + + err = register_bpf_struct_ops(&bpf_psi_bpf_ops, bpf_psi_ops); + if (err) { + pr_warn("error while registering bpf psi struct ops: %d", err); + goto err; + } + + return 0; + +err: + destroy_workqueue(bpf_psi_wq); + return err; +} +late_initcall(bpf_psi_struct_ops_init); diff --git a/kernel/sched/build_utility.c b/kernel/sched/build_utility.c index bf9d8db94b70..80f3799a2fa6 100644 --- a/kernel/sched/build_utility.c +++ b/kernel/sched/build_utility.c @@ -19,6 +19,7 @@ #include #include +#include #include #include #include @@ -92,6 +93,9 @@ #ifdef CONFIG_PSI # include "psi.c" +# ifdef CONFIG_BPF_SYSCALL +# include "bpf_psi.c" +# endif #endif #ifdef CONFIG_MEMBARRIER diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index e1d8eaeeff17..e10fbbc34099 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -201,6 +201,10 @@ static void group_init(struct psi_group *group) init_waitqueue_head(&group->rtpoll_wait); timer_setup(&group->rtpoll_timer, poll_timer_fn, 0); rcu_assign_pointer(group->rtpoll_task, NULL); +#ifdef CONFIG_BPF_SYSCALL + spin_lock_init(&group->bpf_triggers_lock); + INIT_LIST_HEAD(&group->bpf_triggers); +#endif } void __init psi_init(void) @@ -489,10 +493,17 @@ static void update_triggers(struct psi_group *group, u64 now, /* Generate an event */ if (cmpxchg(&t->event, 0, 1) == 0) { - if (t->type == PSI_CGROUP) - kernfs_notify(t->of->kn); - else + switch (t->type) { + case PSI_SYSTEM: wake_up_interruptible(&t->event_wait); + break; + case PSI_CGROUP: + kernfs_notify(t->of->kn); + break; + case PSI_BPF: + bpf_psi_handle_event(t); + break; + } } t->last_event_time = now; /* Reset threshold breach flag once event got generated */ @@ -1125,6 +1136,7 @@ void psi_cgroup_free(struct cgroup *cgroup) return; cancel_delayed_work_sync(&cgroup->psi->avgs_work); + bpf_psi_cgroup_free(cgroup); free_percpu(cgroup->psi->pcpu); /* All triggers must be removed by now */ WARN_ONCE(cgroup->psi->rtpoll_states, "psi: trigger leak\n"); @@ -1356,6 +1368,9 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, case PSI_CGROUP: t->of = params->of; break; + case PSI_BPF: + bpf_psi_add_trigger(t, params); + break; } t->pending_event = false; @@ -1369,8 +1384,10 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, task = kthread_create(psi_rtpoll_worker, group, "psimon"); if (IS_ERR(task)) { - kfree(t); mutex_unlock(&group->rtpoll_trigger_lock); + if (t->type == PSI_BPF) + bpf_psi_remove_trigger(t); + kfree(t); return ERR_CAST(task); } atomic_set(&group->rtpoll_wakeup, 0); @@ -1414,10 +1431,16 @@ void psi_trigger_destroy(struct psi_trigger *t) * being accessed later. Can happen if cgroup is deleted from under a * polling process. */ - if (t->type == PSI_CGROUP) - kernfs_notify(t->of->kn); - else + switch (t->type) { + case PSI_SYSTEM: wake_up_interruptible(&t->event_wait); + break; + case PSI_CGROUP: + kernfs_notify(t->of->kn); + break; + case PSI_BPF: + break; + } if (t->aggregator == PSI_AVGS) { mutex_lock(&group->avgs_lock); @@ -1494,10 +1517,16 @@ __poll_t psi_trigger_poll(void **trigger_ptr, if (!t) return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI; - if (t->type == PSI_CGROUP) - kernfs_generic_poll(t->of, wait); - else + switch (t->type) { + case PSI_SYSTEM: poll_wait(file, &t->event_wait, wait); + break; + case PSI_CGROUP: + kernfs_generic_poll(t->of, wait); + break; + case PSI_BPF: + break; + } if (cmpxchg(&t->event, 1, 0) == 1) ret |= EPOLLPRI; -- 2.50.1