[PATCH v4 0/7] sched_ext: Implement core event counters

[Changwoo Min]

The sched_ext core often has to override the BPF scheduler decisions,
and some events could be interesting but not easily visible.

This patchset aims to address such a problem in the following manner:
  - Introduce an infrastructure to collect such events in a scalable and
    extensible way and to expose the collected events to the BPF scheduler
    in a compatible way.
  - Define seven events to be collected.
  - Modify scx schedulers to demonstrate the usage of the new BPF APIs.

ChangeLog: v3 -> v4
  - Do not include the already applied patches (1-4) from the patchset.
  - Add a missing scx_agg_event() for SCX_EV_ENQ_SKIP_EXITINGk.
  - Move SCX_EV_BYPASS_DISPATCH loggig to select_task_rq_scx() and
    do_enqueue_task().
  - Move scx_bypass_timestamp inside the scx_ops_bypass function
    (renamed to bypass_timestamp).

ChangeLog: v2 -> v3
  - Rename scx_bpf_event_stats() to scx_bpf_events().
  - Add a prefix SCX_EV_ to all event names.
  - Change the implementation SCX_EV_SELECT_CPU_FALLBACK such that
    record the selected cpu (p->scx.selected_cpu) in
    select_task_rq_scx() and compare it in enqueue_task_scx() to
    reliably count events.
  - Change the implementation of SCX_EV_BYPASS_DISPATCH such that log
    the event where the condition is initially detected.
  - Modify scx_qmap to print the core event counter every second.
  - Remove unnecessary white space in patch 6.

ChangeLog: v1 -> v2
  - Rename scx_event_stat and scx_bpf_event_stat() to scx_event_stats and
    scx_bpf_event_stats().
  - Rename event names following the convention of $COMPONENT_$EVENT.
  - Rename event_stats to event_stats_cpu.
  - Drop the enum scx_event_kind and related macros.
  - Revise scx_add_event() to use this_cpu_add().
  - Add __scx_add_event() to use __this_cpu_add().
  - Move the event counter resetting code to the loading of a BPF scheduler.
  - The bypass-related event is further categorized into three events:
    BYPASS_ACTIVATE, BYPASS_DISPATCH, and BYPASS_DURATION.
  - Revise SELECT_CPU_FALLBACK to capture the case of the chosen CPU is not
    allowed.
  - Move is_cpu_allowed() from core.c to sched.h to use in the
    SELECT_CPU_FALLBACK code.

Changwoo Min (7):
  sched_ext: Add an event, SCX_EV_ENQ_SKIP_EXITING
  sched_ext: Add an event, SCX_EV_BYPASS_ACTIVATE
  sched_ext: Add an event, SCX_EV_BYPASS_DISPATCH
  sched_ext: Add an event, SCX_EV_BYPASS_DURATION
  sched_ext: Add scx_bpf_events() and scx_read_event() for BPF
    schedulers
  sched_ext: Print core event count in scx_central scheduler
  sched_ext: Print core event count in scx_qmap scheduler

 kernel/sched/ext.c                       | 51 ++++++++++++++++++++++--
 tools/sched_ext/include/scx/common.bpf.h |  4 ++
 tools/sched_ext/scx_central.bpf.c        | 21 ++++++++++
 tools/sched_ext/scx_qmap.bpf.c           | 19 +++++++++
 4 files changed, 92 insertions(+), 3 deletions(-)

-- 
2.48.1