diff options
Diffstat (limited to 'kernel/cgroup/rstat.c')
| -rw-r--r-- | kernel/cgroup/rstat.c | 549 |
1 files changed, 549 insertions, 0 deletions
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c new file mode 100644 index 000000000..7006fc8dd --- /dev/null +++ b/kernel/cgroup/rstat.c @@ -0,0 +1,549 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include "cgroup-internal.h" + +#include <linux/sched/cputime.h> + +#include <linux/bpf.h> +#include <linux/btf.h> +#include <linux/btf_ids.h> + +static DEFINE_SPINLOCK(cgroup_rstat_lock); +static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock); + +static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu); + +static struct cgroup_rstat_cpu *cgroup_rstat_cpu(struct cgroup *cgrp, int cpu) +{ + return per_cpu_ptr(cgrp->rstat_cpu, cpu); +} + +/** + * cgroup_rstat_updated - keep track of updated rstat_cpu + * @cgrp: target cgroup + * @cpu: cpu on which rstat_cpu was updated + * + * @cgrp's rstat_cpu on @cpu was updated. Put it on the parent's matching + * rstat_cpu->updated_children list. See the comment on top of + * cgroup_rstat_cpu definition for details. + */ +void cgroup_rstat_updated(struct cgroup *cgrp, int cpu) +{ + raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu); + unsigned long flags; + + /* + * Speculative already-on-list test. This may race leading to + * temporary inaccuracies, which is fine. + * + * Because @parent's updated_children is terminated with @parent + * instead of NULL, we can tell whether @cgrp is on the list by + * testing the next pointer for NULL. + */ + if (data_race(cgroup_rstat_cpu(cgrp, cpu)->updated_next)) + return; + + raw_spin_lock_irqsave(cpu_lock, flags); + + /* put @cgrp and all ancestors on the corresponding updated lists */ + while (true) { + struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu); + struct cgroup *parent = cgroup_parent(cgrp); + struct cgroup_rstat_cpu *prstatc; + + /* + * Both additions and removals are bottom-up. If a cgroup + * is already in the tree, all ancestors are. + */ + if (rstatc->updated_next) + break; + + /* Root has no parent to link it to, but mark it busy */ + if (!parent) { + rstatc->updated_next = cgrp; + break; + } + + prstatc = cgroup_rstat_cpu(parent, cpu); + rstatc->updated_next = prstatc->updated_children; + prstatc->updated_children = cgrp; + + cgrp = parent; + } + + raw_spin_unlock_irqrestore(cpu_lock, flags); +} + +/** + * cgroup_rstat_cpu_pop_updated - iterate and dismantle rstat_cpu updated tree + * @pos: current position + * @root: root of the tree to traversal + * @cpu: target cpu + * + * Walks the updated rstat_cpu tree on @cpu from @root. %NULL @pos starts + * the traversal and %NULL return indicates the end. During traversal, + * each returned cgroup is unlinked from the tree. Must be called with the + * matching cgroup_rstat_cpu_lock held. + * + * The only ordering guarantee is that, for a parent and a child pair + * covered by a given traversal, if a child is visited, its parent is + * guaranteed to be visited afterwards. + */ +static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos, + struct cgroup *root, int cpu) +{ + struct cgroup_rstat_cpu *rstatc; + struct cgroup *parent; + + if (pos == root) + return NULL; + + /* + * We're gonna walk down to the first leaf and visit/remove it. We + * can pick whatever unvisited node as the starting point. + */ + if (!pos) { + pos = root; + /* return NULL if this subtree is not on-list */ + if (!cgroup_rstat_cpu(pos, cpu)->updated_next) + return NULL; + } else { + pos = cgroup_parent(pos); + } + + /* walk down to the first leaf */ + while (true) { + rstatc = cgroup_rstat_cpu(pos, cpu); + if (rstatc->updated_children == pos) + break; + pos = rstatc->updated_children; + } + + /* + * Unlink @pos from the tree. As the updated_children list is + * singly linked, we have to walk it to find the removal point. + * However, due to the way we traverse, @pos will be the first + * child in most cases. The only exception is @root. + */ + parent = cgroup_parent(pos); + if (parent) { + struct cgroup_rstat_cpu *prstatc; + struct cgroup **nextp; + + prstatc = cgroup_rstat_cpu(parent, cpu); + nextp = &prstatc->updated_children; + while (*nextp != pos) { + struct cgroup_rstat_cpu *nrstatc; + + nrstatc = cgroup_rstat_cpu(*nextp, cpu); + WARN_ON_ONCE(*nextp == parent); + nextp = &nrstatc->updated_next; + } + *nextp = rstatc->updated_next; + } + + rstatc->updated_next = NULL; + return pos; +} + +/* + * A hook for bpf stat collectors to attach to and flush their stats. + * Together with providing bpf kfuncs for cgroup_rstat_updated() and + * cgroup_rstat_flush(), this enables a complete workflow where bpf progs that + * collect cgroup stats can integrate with rstat for efficient flushing. + * + * A static noinline declaration here could cause the compiler to optimize away + * the function. A global noinline declaration will keep the definition, but may + * optimize away the callsite. Therefore, __weak is needed to ensure that the + * call is still emitted, by telling the compiler that we don't know what the + * function might eventually be. + * + * __diag_* below are needed to dismiss the missing prototype warning. + */ +__diag_push(); +__diag_ignore_all("-Wmissing-prototypes", + "kfuncs which will be used in BPF programs"); + +__weak noinline void bpf_rstat_flush(struct cgroup *cgrp, + struct cgroup *parent, int cpu) +{ +} + +__diag_pop(); + +/* see cgroup_rstat_flush() */ +static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep) + __releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock) +{ + int cpu; + + lockdep_assert_held(&cgroup_rstat_lock); + + for_each_possible_cpu(cpu) { + raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, + cpu); + struct cgroup *pos = NULL; + unsigned long flags; + + /* + * The _irqsave() is needed because cgroup_rstat_lock is + * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring + * this lock with the _irq() suffix only disables interrupts on + * a non-PREEMPT_RT kernel. The raw_spinlock_t below disables + * interrupts on both configurations. The _irqsave() ensures + * that interrupts are always disabled and later restored. + */ + raw_spin_lock_irqsave(cpu_lock, flags); + while ((pos = cgroup_rstat_cpu_pop_updated(pos, cgrp, cpu))) { + struct cgroup_subsys_state *css; + + cgroup_base_stat_flush(pos, cpu); + bpf_rstat_flush(pos, cgroup_parent(pos), cpu); + + rcu_read_lock(); + list_for_each_entry_rcu(css, &pos->rstat_css_list, + rstat_css_node) + css->ss->css_rstat_flush(css, cpu); + rcu_read_unlock(); + } + raw_spin_unlock_irqrestore(cpu_lock, flags); + + /* if @may_sleep, play nice and yield if necessary */ + if (may_sleep && (need_resched() || + spin_needbreak(&cgroup_rstat_lock))) { + spin_unlock_irq(&cgroup_rstat_lock); + if (!cond_resched()) + cpu_relax(); + spin_lock_irq(&cgroup_rstat_lock); + } + } +} + +/** + * cgroup_rstat_flush - flush stats in @cgrp's subtree + * @cgrp: target cgroup + * + * Collect all per-cpu stats in @cgrp's subtree into the global counters + * and propagate them upwards. After this function returns, all cgroups in + * the subtree have up-to-date ->stat. + * + * This also gets all cgroups in the subtree including @cgrp off the + * ->updated_children lists. + * + * This function may block. + */ +void cgroup_rstat_flush(struct cgroup *cgrp) +{ + might_sleep(); + + spin_lock_irq(&cgroup_rstat_lock); + cgroup_rstat_flush_locked(cgrp, true); + spin_unlock_irq(&cgroup_rstat_lock); +} + +/** + * cgroup_rstat_flush_irqsafe - irqsafe version of cgroup_rstat_flush() + * @cgrp: target cgroup + * + * This function can be called from any context. + */ +void cgroup_rstat_flush_irqsafe(struct cgroup *cgrp) +{ + unsigned long flags; + + spin_lock_irqsave(&cgroup_rstat_lock, flags); + cgroup_rstat_flush_locked(cgrp, false); + spin_unlock_irqrestore(&cgroup_rstat_lock, flags); +} + +/** + * cgroup_rstat_flush_hold - flush stats in @cgrp's subtree and hold + * @cgrp: target cgroup + * + * Flush stats in @cgrp's subtree and prevent further flushes. Must be + * paired with cgroup_rstat_flush_release(). + * + * This function may block. + */ +void cgroup_rstat_flush_hold(struct cgroup *cgrp) + __acquires(&cgroup_rstat_lock) +{ + might_sleep(); + spin_lock_irq(&cgroup_rstat_lock); + cgroup_rstat_flush_locked(cgrp, true); +} + +/** + * cgroup_rstat_flush_release - release cgroup_rstat_flush_hold() + */ +void cgroup_rstat_flush_release(void) + __releases(&cgroup_rstat_lock) +{ + spin_unlock_irq(&cgroup_rstat_lock); +} + +int cgroup_rstat_init(struct cgroup *cgrp) +{ + int cpu; + + /* the root cgrp has rstat_cpu preallocated */ + if (!cgrp->rstat_cpu) { + cgrp->rstat_cpu = alloc_percpu(struct cgroup_rstat_cpu); + if (!cgrp->rstat_cpu) + return -ENOMEM; + } + + /* ->updated_children list is self terminated */ + for_each_possible_cpu(cpu) { + struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu); + + rstatc->updated_children = cgrp; + u64_stats_init(&rstatc->bsync); + } + + return 0; +} + +void cgroup_rstat_exit(struct cgroup *cgrp) +{ + int cpu; + + cgroup_rstat_flush(cgrp); + + /* sanity check */ + for_each_possible_cpu(cpu) { + struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu); + + if (WARN_ON_ONCE(rstatc->updated_children != cgrp) || + WARN_ON_ONCE(rstatc->updated_next)) + return; + } + + free_percpu(cgrp->rstat_cpu); + cgrp->rstat_cpu = NULL; +} + +void __init cgroup_rstat_boot(void) +{ + int cpu; + + for_each_possible_cpu(cpu) + raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu)); +} + +/* + * Functions for cgroup basic resource statistics implemented on top of + * rstat. + */ +static void cgroup_base_stat_add(struct cgroup_base_stat *dst_bstat, + struct cgroup_base_stat *src_bstat) +{ + dst_bstat->cputime.utime += src_bstat->cputime.utime; + dst_bstat->cputime.stime += src_bstat->cputime.stime; + dst_bstat->cputime.sum_exec_runtime += src_bstat->cputime.sum_exec_runtime; +#ifdef CONFIG_SCHED_CORE + dst_bstat->forceidle_sum += src_bstat->forceidle_sum; +#endif +} + +static void cgroup_base_stat_sub(struct cgroup_base_stat *dst_bstat, + struct cgroup_base_stat *src_bstat) +{ + dst_bstat->cputime.utime -= src_bstat->cputime.utime; + dst_bstat->cputime.stime -= src_bstat->cputime.stime; + dst_bstat->cputime.sum_exec_runtime -= src_bstat->cputime.sum_exec_runtime; +#ifdef CONFIG_SCHED_CORE + dst_bstat->forceidle_sum -= src_bstat->forceidle_sum; +#endif +} + +static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu) +{ + struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu); + struct cgroup *parent = cgroup_parent(cgrp); + struct cgroup_base_stat delta; + unsigned seq; + + /* Root-level stats are sourced from system-wide CPU stats */ + if (!parent) + return; + + /* fetch the current per-cpu values */ + do { + seq = __u64_stats_fetch_begin(&rstatc->bsync); + delta = rstatc->bstat; + } while (__u64_stats_fetch_retry(&rstatc->bsync, seq)); + + /* propagate percpu delta to global */ + cgroup_base_stat_sub(&delta, &rstatc->last_bstat); + cgroup_base_stat_add(&cgrp->bstat, &delta); + cgroup_base_stat_add(&rstatc->last_bstat, &delta); + + /* propagate global delta to parent (unless that's root) */ + if (cgroup_parent(parent)) { + delta = cgrp->bstat; + cgroup_base_stat_sub(&delta, &cgrp->last_bstat); + cgroup_base_stat_add(&parent->bstat, &delta); + cgroup_base_stat_add(&cgrp->last_bstat, &delta); + } +} + +static struct cgroup_rstat_cpu * +cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp, unsigned long *flags) +{ + struct cgroup_rstat_cpu *rstatc; + + rstatc = get_cpu_ptr(cgrp->rstat_cpu); + *flags = u64_stats_update_begin_irqsave(&rstatc->bsync); + return rstatc; +} + +static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp, + struct cgroup_rstat_cpu *rstatc, + unsigned long flags) +{ + u64_stats_update_end_irqrestore(&rstatc->bsync, flags); + cgroup_rstat_updated(cgrp, smp_processor_id()); + put_cpu_ptr(rstatc); +} + +void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec) +{ + struct cgroup_rstat_cpu *rstatc; + unsigned long flags; + + rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags); + rstatc->bstat.cputime.sum_exec_runtime += delta_exec; + cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags); +} + +void __cgroup_account_cputime_field(struct cgroup *cgrp, + enum cpu_usage_stat index, u64 delta_exec) +{ + struct cgroup_rstat_cpu *rstatc; + unsigned long flags; + + rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags); + + switch (index) { + case CPUTIME_USER: + case CPUTIME_NICE: + rstatc->bstat.cputime.utime += delta_exec; + break; + case CPUTIME_SYSTEM: + case CPUTIME_IRQ: + case CPUTIME_SOFTIRQ: + rstatc->bstat.cputime.stime += delta_exec; + break; +#ifdef CONFIG_SCHED_CORE + case CPUTIME_FORCEIDLE: + rstatc->bstat.forceidle_sum += delta_exec; + break; +#endif + default: + break; + } + + cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags); +} + +/* + * compute the cputime for the root cgroup by getting the per cpu data + * at a global level, then categorizing the fields in a manner consistent + * with how it is done by __cgroup_account_cputime_field for each bit of + * cpu time attributed to a cgroup. + */ +static void root_cgroup_cputime(struct cgroup_base_stat *bstat) +{ + struct task_cputime *cputime = &bstat->cputime; + int i; + + memset(bstat, 0, sizeof(*bstat)); + for_each_possible_cpu(i) { + struct kernel_cpustat kcpustat; + u64 *cpustat = kcpustat.cpustat; + u64 user = 0; + u64 sys = 0; + + kcpustat_cpu_fetch(&kcpustat, i); + + user += cpustat[CPUTIME_USER]; + user += cpustat[CPUTIME_NICE]; + cputime->utime += user; + + sys += cpustat[CPUTIME_SYSTEM]; + sys += cpustat[CPUTIME_IRQ]; + sys += cpustat[CPUTIME_SOFTIRQ]; + cputime->stime += sys; + + cputime->sum_exec_runtime += user; + cputime->sum_exec_runtime += sys; + cputime->sum_exec_runtime += cpustat[CPUTIME_STEAL]; + +#ifdef CONFIG_SCHED_CORE + bstat->forceidle_sum += cpustat[CPUTIME_FORCEIDLE]; +#endif + } +} + +void cgroup_base_stat_cputime_show(struct seq_file *seq) +{ + struct cgroup *cgrp = seq_css(seq)->cgroup; + u64 usage, utime, stime; + struct cgroup_base_stat bstat; +#ifdef CONFIG_SCHED_CORE + u64 forceidle_time; +#endif + + if (cgroup_parent(cgrp)) { + cgroup_rstat_flush_hold(cgrp); + usage = cgrp->bstat.cputime.sum_exec_runtime; + cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime, + &utime, &stime); +#ifdef CONFIG_SCHED_CORE + forceidle_time = cgrp->bstat.forceidle_sum; +#endif + cgroup_rstat_flush_release(); + } else { + root_cgroup_cputime(&bstat); + usage = bstat.cputime.sum_exec_runtime; + utime = bstat.cputime.utime; + stime = bstat.cputime.stime; +#ifdef CONFIG_SCHED_CORE + forceidle_time = bstat.forceidle_sum; +#endif + } + + do_div(usage, NSEC_PER_USEC); + do_div(utime, NSEC_PER_USEC); + do_div(stime, NSEC_PER_USEC); +#ifdef CONFIG_SCHED_CORE + do_div(forceidle_time, NSEC_PER_USEC); +#endif + + seq_printf(seq, "usage_usec %llu\n" + "user_usec %llu\n" + "system_usec %llu\n", + usage, utime, stime); + +#ifdef CONFIG_SCHED_CORE + seq_printf(seq, "core_sched.force_idle_usec %llu\n", forceidle_time); +#endif +} + +/* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */ +BTF_SET8_START(bpf_rstat_kfunc_ids) +BTF_ID_FLAGS(func, cgroup_rstat_updated) +BTF_ID_FLAGS(func, cgroup_rstat_flush, KF_SLEEPABLE) +BTF_SET8_END(bpf_rstat_kfunc_ids) + +static const struct btf_kfunc_id_set bpf_rstat_kfunc_set = { + .owner = THIS_MODULE, + .set = &bpf_rstat_kfunc_ids, +}; + +static int __init bpf_rstat_kfunc_init(void) +{ + return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, + &bpf_rstat_kfunc_set); +} +late_initcall(bpf_rstat_kfunc_init); |