This series adds bpf kfuncs for the cgroup CPU controller, following the memory controller kfuncs in mm/bpf_memcontrol.c.
Collecting cgroup statistics is expensive: the existing method is to open and parse a cgroup file. memcg already has an efficient alternative through BPF; this series extends that idea to cpu. Design: - Leave reading the CFS bandwidth counters to the BPF program. They are plain fields of tg->cfs_bandwidth, so they need no kernel code. - Add one kfunc to compute the throttled time. This is necessary because it is a sum over every possible cpu, which a user cannot do itself. - The bpf_cpu_cgroup_cputime() returns all five base CPU-time values in one call with one cputime_adjust(). The only part it touches the scheduler part is to discard the static for throttled_time_self() in order to use externally. The two kfuncs that take the rstat lock are KF_SLEEPABLE following idea in the mm/bpf_memcontrol.c Suggested-by: Shakeel Butt <[email protected]> Assisted-by: Claude:claude-opus-5 Signed-off-by: Ziyang Men <[email protected]> --- include/linux/cgroup.h | 15 +++++++ kernel/cgroup/Makefile | 2 + kernel/cgroup/bpf_cpu.c | 80 +++++++++++++++++++++++++++++++++ kernel/cgroup/cgroup-internal.h | 3 ++ kernel/cgroup/rstat.c | 42 +++++++++++++++++ kernel/sched/core.c | 2 +- 6 files changed, 143 insertions(+), 1 deletion(-) create mode 100644 kernel/cgroup/bpf_cpu.c diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index f2aa46a4f871..d2a6b5efad51 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -923,4 +923,19 @@ struct cgroup *task_get_cgroup1(struct task_struct *tsk, int hierarchy_id); struct cgroup_of_peak *of_peak(struct kernfs_open_file *of); +/* A cgroup's base CPU-time counters in microseconds, as cpu.stat prints them */ +struct cpu_cgroup_cputime { + u64 usage_usec; + u64 user_usec; + u64 system_usec; + u64 nice_usec; + u64 forceidle_usec; /* 0 without CONFIG_SCHED_CORE */ +}; + +/* A task_group's own throttled time in nanoseconds; see cpu.stat.local */ +struct task_group; +#ifdef CONFIG_CFS_BANDWIDTH +u64 throttled_time_self(struct task_group *tg); +#endif + #endif /* _LINUX_CGROUP_H */ diff --git a/kernel/cgroup/Makefile b/kernel/cgroup/Makefile index ede31601a363..0ba59b7eef48 100644 --- a/kernel/cgroup/Makefile +++ b/kernel/cgroup/Makefile @@ -1,6 +1,8 @@ # SPDX-License-Identifier: GPL-2.0 obj-y := cgroup.o rstat.o namespace.o cgroup-v1.o freezer.o +obj-$(CONFIG_BPF_SYSCALL) += bpf_cpu.o + obj-$(CONFIG_CGROUP_FREEZER) += legacy_freezer.o obj-$(CONFIG_CGROUP_PIDS) += pids.o obj-$(CONFIG_CGROUP_RDMA) += rdma.o diff --git a/kernel/cgroup/bpf_cpu.c b/kernel/cgroup/bpf_cpu.c new file mode 100644 index 000000000000..6eb89c8e84fd --- /dev/null +++ b/kernel/cgroup/bpf_cpu.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * CPU Controller-related BPF kfuncs + * + * bpf_cpu_cgroup_cputime() is defined in rstat.c, which owns the locking it + * needs, and only registered here. + * + * Author: Ziyang Men <[email protected]> + */ + +#include <linux/bpf.h> +#include <linux/btf_ids.h> +#include <linux/cgroup.h> + +#include "cgroup-internal.h" + +__bpf_kfunc_start_defs(); + +/** + * bpf_cpu_cgroup_flush_stats - Flush a cgroup's base CPU-time statistics + * @cgrp: cgroup to flush + * + * Propagate the cgroup's base CPU-time statistics up the cgroup tree. + */ +__bpf_kfunc void bpf_cpu_cgroup_flush_stats(struct cgroup *cgrp) +{ + css_rstat_flush(&cgrp->self); +} + +/** + * bpf_cpu_cgroup_throttled_self - Read a cgroup's own throttled time + * @cgrp: cgroup to read from + * + * Return: The throttled time in microseconds, or 0 if config is off. + */ +__bpf_kfunc u64 bpf_cpu_cgroup_throttled_self(struct cgroup *cgrp) +{ +/* cpu_cgrp_id needs the cpu controller, which CFS bandwidth depends on */ +#ifdef CONFIG_CFS_BANDWIDTH + struct cgroup_subsys_state *css; + + guard(rcu)(); + + css = rcu_dereference(cgrp->subsys[cpu_cgrp_id]); + if (!css) + return 0; + + return div_u64(throttled_time_self((struct task_group *)css), + NSEC_PER_USEC); +#else + return 0; +#endif +} + +__bpf_kfunc_end_defs(); + +/* KF_SLEEPABLE keeps the rstat spinlock out of NMI */ +BTF_KFUNCS_START(bpf_cpu_cgroup_kfunc_ids) +BTF_ID_FLAGS(func, bpf_cpu_cgroup_flush_stats, KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_cpu_cgroup_cputime, KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_cpu_cgroup_throttled_self) +BTF_KFUNCS_END(bpf_cpu_cgroup_kfunc_ids) + +static const struct btf_kfunc_id_set bpf_cpu_cgroup_kfunc_set = { + .owner = THIS_MODULE, + .set = &bpf_cpu_cgroup_kfunc_ids, +}; + +static int __init bpf_cpu_cgroup_kfunc_init(void) +{ + int err; + + err = register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC, + &bpf_cpu_cgroup_kfunc_set); + if (err) + pr_warn("error while registering cpu cgroup kfuncs: %d\n", err); + + return err; +} +late_initcall(bpf_cpu_cgroup_kfunc_init); diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h index 58797123b752..65f5b6318289 100644 --- a/kernel/cgroup/cgroup-internal.h +++ b/kernel/cgroup/cgroup-internal.h @@ -271,6 +271,9 @@ int css_rstat_init(struct cgroup_subsys_state *css); void css_rstat_exit(struct cgroup_subsys_state *css); int ss_rstat_init(struct cgroup_subsys *ss); void cgroup_base_stat_cputime_show(struct seq_file *seq); +#ifdef CONFIG_BPF_SYSCALL +void bpf_cpu_cgroup_cputime(struct cgroup *cgrp, struct cpu_cgroup_cputime *out); +#endif /* * namespace.c diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c index de816a43db9f..f9e30719068e 100644 --- a/kernel/cgroup/rstat.c +++ b/kernel/cgroup/rstat.c @@ -752,6 +752,48 @@ void cgroup_base_stat_cputime_show(struct seq_file *seq) cgroup_force_idle_show(seq, &bstat); } +#ifdef CONFIG_BPF_SYSCALL + +__bpf_kfunc_start_defs(); + +/** + * bpf_cpu_cgroup_cputime - Read a cgroup's base CPU-time data + * @cgrp: cgroup to read from + * @out: the data in microseconds. Zero it first: the verifier reads the + * whole struct. + * + * Adjust once and fill all values. + */ +__bpf_kfunc void bpf_cpu_cgroup_cputime(struct cgroup *cgrp, + struct cpu_cgroup_cputime *out) +{ + struct cgroup_base_stat bstat; + + if (cgroup_parent(cgrp)) { + __css_rstat_lock(&cgrp->self, -1); + bstat = cgrp->bstat; + cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime, + &bstat.cputime.utime, &bstat.cputime.stime); + __css_rstat_unlock(&cgrp->self, -1); + } else { + root_cgroup_cputime(&bstat); + } + + out->usage_usec = div_u64(bstat.cputime.sum_exec_runtime, NSEC_PER_USEC); + out->user_usec = div_u64(bstat.cputime.utime, NSEC_PER_USEC); + out->system_usec = div_u64(bstat.cputime.stime, NSEC_PER_USEC); + out->nice_usec = div_u64(bstat.ntime, NSEC_PER_USEC); +#ifdef CONFIG_SCHED_CORE + out->forceidle_usec = div_u64(bstat.forceidle_sum, NSEC_PER_USEC); +#else + out->forceidle_usec = 0; +#endif +} + +__bpf_kfunc_end_defs(); + +#endif /* CONFIG_BPF_SYSCALL */ + /* Add bpf kfuncs for css_rstat_updated() and css_rstat_flush() */ BTF_KFUNCS_START(bpf_rstat_kfunc_ids) BTF_ID_FLAGS(func, css_rstat_updated) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 96226707c2f6..75735e0e81ef 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -10027,7 +10027,7 @@ static int cpu_cfs_stat_show(struct seq_file *sf, void *v) return 0; } -static u64 throttled_time_self(struct task_group *tg) +u64 throttled_time_self(struct task_group *tg) { int i; u64 total = 0; -- 2.53.0-Meta
