From: Roman Gushchin <guro@fb.com>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Mel Gorman <mgorman@techsingularity.net>, <bpf@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH rfc 2/6] bpf: sched: add convenient helpers to identify sched entities
Date: Fri, 26 Nov 2021 11:50:15 -0800 [thread overview]
Message-ID: <YaE6d9NhXCN9i2sM@carbon.dhcp.thefacebook.com> (raw)
In-Reply-To: <1334F6BA-BAE1-4FF8-B84C-3C1AE733CA7A@gmail.com>
On Thu, Nov 25, 2021 at 02:09:00PM +0800, Yafang Shao wrote:
>
>
> > On Sep 17, 2021, at 12:24 AM, Roman Gushchin <guro@fb.com> wrote:
> >
> > This patch adds 3 helpers useful for dealing with sched entities:
> > u64 bpf_sched_entity_to_tgidpid(struct sched_entity *se);
> > u64 bpf_sched_entity_to_cgrpid(struct sched_entity *se);
> > long bpf_sched_entity_belongs_to_cgrp(struct sched_entity *se, u64 cgrpid);
> >
> > Sched entity is a basic structure used by the scheduler to represent
> > schedulable objects: tasks and cgroups (if CONFIG_FAIR_GROUP_SCHED
> > is enabled). It will be passed as an argument to many bpf hooks, so
> > scheduler bpf programs need a convenient way to deal with it.
> >
> > bpf_sched_entity_to_tgidpid() and bpf_sched_entity_to_cgrpid() are
> > useful to identify a sched entity in userspace terms (pid, tgid and
> > cgroup id). bpf_sched_entity_belongs_to_cgrp() allows to check whether
> > a sched entity belongs to sub-tree of a cgroup. It allows to write
> > cgroup-specific scheduler policies even without enabling the cgroup
> > cpu controller.
> >
> > Signed-off-by: Roman Gushchin <guro@fb.com>
> > ---
> > include/uapi/linux/bpf.h | 23 +++++++++++
> > kernel/sched/bpf_sched.c | 74 ++++++++++++++++++++++++++++++++++
> > scripts/bpf_doc.py | 2 +
> > tools/include/uapi/linux/bpf.h | 23 +++++++++++
> > 4 files changed, 122 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 6dfbebb8fc8f..199e4a92820d 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -4900,6 +4900,26 @@ union bpf_attr {
> > * **-EINVAL** if *flags* is not zero.
> > *
> > * **-ENOENT** if architecture does not support branch records.
> > + *
> > + * u64 bpf_sched_entity_to_tgidpid(struct sched_entity *se)
> > + * Description
> > + * Return task's encoded tgid and pid if the sched entity is a task.
> > + * Return
> > + * Tgid and pid encoded as tgid << 32 \| pid, if *se* is a task. (u64)-1 otherwise.
> > + *
> > + * u64 bpf_sched_entity_to_cgrpid(struct sched_entity *se)
> > + * Description
> > + * Return cgroup id if the given sched entity is a cgroup.
> > + * Return
> > + * Cgroup id, if *se* is a cgroup. (u64)-1 otherwise.
> > + *
> > + * long bpf_sched_entity_belongs_to_cgrp(struct sched_entity *se, u64 cgrpid)
> > + * Description
> > + * Checks whether the sched entity belongs to a cgroup or
> > + * it's sub-tree. It doesn't require a cgroup CPU controller
> > + * to be enabled.
> > + * Return
> > + * 1 if the sched entity belongs to a cgroup, 0 otherwise.
> > */
> > #define __BPF_FUNC_MAPPER(FN) \
> > FN(unspec), \
> > @@ -5079,6 +5099,9 @@ union bpf_attr {
> > FN(get_attach_cookie), \
> > FN(task_pt_regs), \
> > FN(get_branch_snapshot), \
> > + FN(sched_entity_to_tgidpid), \
> > + FN(sched_entity_to_cgrpid), \
> > + FN(sched_entity_belongs_to_cgrp), \
> > /* */
> >
> > /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> > diff --git a/kernel/sched/bpf_sched.c b/kernel/sched/bpf_sched.c
> > index 2f05c186cfd0..ead691dc6e85 100644
> > --- a/kernel/sched/bpf_sched.c
> > +++ b/kernel/sched/bpf_sched.c
> > @@ -42,12 +42,86 @@ int bpf_sched_verify_prog(struct bpf_verifier_log *vlog,
> > return 0;
> > }
> >
> > +BPF_CALL_1(bpf_sched_entity_to_tgidpid, struct sched_entity *, se)
> > +{
> > + if (entity_is_task(se)) {
> > + struct task_struct *task = task_of(se);
> > +
> > + return (u64) task->tgid << 32 | task->pid;
> > + } else {
> > + return (u64) -1;
> > + }
> > +}
> > +
> > +BPF_CALL_1(bpf_sched_entity_to_cgrpid, struct sched_entity *, se)
> > +{
> > +#ifdef CONFIG_FAIR_GROUP_SCHED
> > + if (!entity_is_task(se))
> > + return cgroup_id(se->cfs_rq->tg->css.cgroup);
> > +#endif
> > + return (u64) -1;
> > +}
> > +
> > +BPF_CALL_2(bpf_sched_entity_belongs_to_cgrp, struct sched_entity *, se,
> > + u64, cgrpid)
> > +{
> > +#ifdef CONFIG_CGROUPS
> > + struct cgroup *cgrp;
> > + int level;
> > +
> > + if (entity_is_task(se))
> > + cgrp = task_dfl_cgroup(task_of(se));
> > +#ifdef CONFIG_FAIR_GROUP_SCHED
> > + else
> > + cgrp = se->cfs_rq->tg->css.cgroup;
>
> It is incorrect.
> It should use se->my_q->tg->css.cgroup and some possible NULL check. (for autogroup)
> se->cfs_rq and se->my_q are different. se->my_q is the cfs_rq of this se itself, while the se->cfs_rq may be the parent.
Indeed. Thanks, will fix in the next version.
next prev parent reply other threads:[~2021-11-26 19:52 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210915213550.3696532-1-guro@fb.com>
2021-09-16 0:19 ` [PATCH rfc 0/6] Scheduler BPF Hao Luo
2021-09-16 1:42 ` Roman Gushchin
2021-09-16 16:24 ` Roman Gushchin
2021-09-16 16:24 ` [PATCH rfc 1/6] bpf: sched: basic infrastructure for scheduler bpf Roman Gushchin
2021-09-16 16:24 ` [PATCH rfc 2/6] bpf: sched: add convenient helpers to identify sched entities Roman Gushchin
2021-11-25 6:09 ` Yafang Shao
2021-11-26 19:50 ` Roman Gushchin [this message]
2021-09-16 16:24 ` [PATCH rfc 3/6] bpf: sched: introduce bpf_sched_enable() Roman Gushchin
2021-09-16 16:24 ` [PATCH rfc 4/6] sched: cfs: add bpf hooks to control wakeup and tick preemption Roman Gushchin
2021-10-01 3:35 ` Barry Song
2021-10-02 0:13 ` Roman Gushchin
2021-09-16 16:24 ` [PATCH rfc 5/6] libbpf: add support for scheduler bpf programs Roman Gushchin
2021-09-16 16:24 ` [PATCH rfc 6/6] bpftool: recognize scheduler programs Roman Gushchin
2021-09-16 16:36 ` [PATCH rfc 0/6] Scheduler BPF Roman Gushchin
2021-10-06 16:39 ` Qais Yousef
2021-10-06 18:50 ` Roman Gushchin
2021-10-11 16:38 ` Qais Yousef
2021-10-11 18:09 ` Roman Gushchin
2021-10-12 10:16 ` Qais Yousef
[not found] ` <52EC1E80-4C89-43AD-8A59-8ACA184EAE53@gmail.com>
2021-11-25 6:00 ` Yafang Shao
2021-11-26 19:46 ` Roman Gushchin
2022-01-15 8:29 ` Huichun Feng
2022-01-18 22:54 ` Roman Gushchin
2022-07-19 13:05 ` Ren Zhijie
2022-07-19 13:17 ` Ren Zhijie
2022-07-19 23:21 ` Roman Gushchin
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