linux-kernel - [PATCH v2 0/2] sched_ext: Add a core event and update scx schedulers

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Message-ID: <20250207064052.399227-1-changwoo@igalia.com>
Date: Fri,  7 Feb 2025 15:40:50 +0900
From: Changwoo Min <changwoo@...lia.com>
To: tj@...nel.org,
	void@...ifault.com,
	arighi@...dia.com
Cc: kernel-dev@...lia.com,
	linux-kernel@...r.kernel.org,
	Changwoo Min <changwoo@...lia.com>
Subject: [PATCH v2 0/2] sched_ext: Add a core event and update scx schedulers

This patchset introduces a new event, SCX_EV_ENQ_SLICE_DFL, and updates
two scx schedulers -- scx_qmap and scx_central -- to print out the new
event.

SCX_EV_ENQ_SLICE_DFL counts how many times the tasks' time slice is set
to the default value (SCX_SLICE_DFL) by the sched_ext core in the enqueue
and pick_next paths.

Scheduling a task with SCX_SLICE_DFL unintentionally would be a source
of latency spikes because SCX_SLICE_DFL is relatively long (20 msec).
Thus, soaring the SCX_EV_ENQ_SLICE_DFL value would be a sign of BPF
scheduler bugs, causing latency spikes.

ChangeLog v1 -> v2:
  - Instrument the event at select_task_rq_scx() when ops.select_cpu()
    is not provided.

Changwoo Min (2):
  sched_ext: Add an event, SCX_EV_ENQ_SLICE_DFL
  sched_ext: Print an event, SCX_EV_ENQ_SLICE_DFL, in scx_qmap/central

 kernel/sched/ext.c                | 16 +++++++++++++++-
 tools/sched_ext/scx_central.bpf.c |  2 ++
 tools/sched_ext/scx_qmap.bpf.c    |  2 ++
 3 files changed, 19 insertions(+), 1 deletion(-)

-- 
2.48.1