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 <yosryahmed@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/r/20220824233117.1312810-4-haoluo@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Yosry Ahmed 2022-08-24 16:31:15 -07:00 committed by Alexei Starovoitov
parent fe0dd9d4b7
commit a319185be9

View File

@ -3,6 +3,10 @@
#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);
@ -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);