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sched_ext: Add cgroup support

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Add sched_ext_ops operations to init/exit cgroups, and track task migrations
and config changes. A BPF scheduler may not implement or implement only
subset of cgroup features. The implemented features can be indicated using
%SCX_OPS_HAS_CGOUP_* flags. If cgroup configuration makes use of features
that are not implemented, a warning is triggered.

While a BPF scheduler is being enabled and disabled, relevant cgroup
operations are locked out using scx_cgroup_rwsem. This avoids situations
like task prep taking place while the task is being moved across cgroups,
making things easier for BPF schedulers.

v7: - cgroup interface file visibility toggling is dropped in favor just
      warning messages. Dynamically changing interface visiblity caused more
      confusion than helping.

v6: - Updated to reflect the removal of SCX_KF_SLEEPABLE.

    - Updated to use CONFIG_GROUP_SCHED_WEIGHT and fixes for
      !CONFIG_FAIR_GROUP_SCHED && CONFIG_EXT_GROUP_SCHED.

v5: - Flipped the locking order between scx_cgroup_rwsem and
      cpus_read_lock() to avoid locking order conflict w/ cpuset. Better
      documentation around locking.

    - sched_move_task() takes an early exit if the source and destination
      are identical. This triggered the warning in scx_cgroup_can_attach()
      as it left p->scx.cgrp_moving_from uncleared. Updated the cgroup
      migration path so that ops.cgroup_prep_move() is skipped for identity
      migrations so that its invocations always match ops.cgroup_move()
      one-to-one.

v4: - Example schedulers moved into their own patches.

    - Fix build failure when !CONFIG_CGROUP_SCHED, reported by Andrea Righi.

v3: - Make scx_example_pair switch all tasks by default.

    - Convert to BPF inline iterators.

    - scx_bpf_task_cgroup() is added to determine the current cgroup from
      CPU controller's POV. This allows BPF schedulers to accurately track
      CPU cgroup membership.

    - scx_example_flatcg added. This demonstrates flattened hierarchy
      implementation of CPU cgroup control and shows significant performance
      improvement when cgroups which are nested multiple levels are under
      competition.

v2: - Build fixes for different CONFIG combinations.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Andrea Righi <andrea.righi@canonical.com>
This commit is contained in:
Tejun Heo
2024-09-04 10:24:59 -10:00
parent e179e80c5d
commit 8195136669
8 changed files with 636 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
tools/testing/selftests/sched_ext/maximal.bpf.c
View File

@@ -95,6 +95,32 @@ void BPF_STRUCT_OPS(maximal_exit_task, struct task_struct *p,
void BPF_STRUCT_OPS(maximal_disable, struct task_struct *p)
{}
s32 BPF_STRUCT_OPS(maximal_cgroup_init, struct cgroup *cgrp,
struct scx_cgroup_init_args *args)
{
return 0;
}
void BPF_STRUCT_OPS(maximal_cgroup_exit, struct cgroup *cgrp)
{}
s32 BPF_STRUCT_OPS(maximal_cgroup_prep_move, struct task_struct *p,
struct cgroup *from, struct cgroup *to)
{
return 0;
}
void BPF_STRUCT_OPS(maximal_cgroup_move, struct task_struct *p,
struct cgroup *from, struct cgroup *to)
{}
void BPF_STRUCT_OPS(maximal_cgroup_cancel_move, struct task_struct *p,
struct cgroup *from, struct cgroup *to)
{}
void BPF_STRUCT_OPS(maximal_cgroup_set_weight, struct cgroup *cgrp, u32 weight)
{}
s32 BPF_STRUCT_OPS_SLEEPABLE(maximal_init)
{
return 0;
@@ -126,6 +152,12 @@ struct sched_ext_ops maximal_ops = {
.enable = maximal_enable,
.exit_task = maximal_exit_task,
.disable = maximal_disable,
.cgroup_init = maximal_cgroup_init,
.cgroup_exit = maximal_cgroup_exit,
.cgroup_prep_move = maximal_cgroup_prep_move,
.cgroup_move = maximal_cgroup_move,
.cgroup_cancel_move = maximal_cgroup_cancel_move,
.cgroup_set_weight = maximal_cgroup_set_weight,
.init = maximal_init,
.exit = maximal_exit,
.name = "maximal",