From a319185be9f5ad13c2a296d448ac52ffe45d194c Mon Sep 17 00:00:00 2001 From: Yosry Ahmed Date: Wed, 24 Aug 2022 16:31:15 -0700 Subject: cgroup: bpf: enable bpf programs to integrate with rstat Enable bpf programs to make use of rstat to collect cgroup hierarchical stats efficiently: - Add cgroup_rstat_updated() kfunc, for bpf progs that collect stats. - Add cgroup_rstat_flush() sleepable kfunc, for bpf progs that read stats. - Add an empty bpf_rstat_flush() hook that is called during rstat flushing, for bpf progs that flush stats to attach to. Attaching a bpf prog to this hook effectively registers it as a flush callback. Signed-off-by: Yosry Ahmed Acked-by: Tejun Heo Signed-off-by: Hao Luo Link: https://lore.kernel.org/r/20220824233117.1312810-4-haoluo@google.com Signed-off-by: Alexei Starovoitov --- kernel/cgroup/rstat.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) (limited to 'kernel/cgroup') diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c index feb59380c896..793ecff29038 100644 --- a/kernel/cgroup/rstat.c +++ b/kernel/cgroup/rstat.c @@ -3,6 +3,10 @@ #include +#include +#include +#include + static DEFINE_SPINLOCK(cgroup_rstat_lock); static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock); @@ -141,6 +145,31 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos, 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) @@ -168,6 +197,7 @@ static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep) 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, @@ -501,3 +531,21 @@ void cgroup_base_stat_cputime_show(struct seq_file *seq) 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); -- cgit v1.2.3