sched_ext: Add shard boundaries to scx_bpf_cid_override()

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An overridden cid mapping invalidates the auto-generated shard layout, so
the override call has to provide both. Extend scx_bpf_cid_override() with a
shard_start[] array that lists the first cid of each shard (starting at 0,
strictly increasing, last shard implicitly extends to num_possible_cpus()).

A scheduler that wants only custom shards with the auto-generated cid
mapping can read the current mapping and pass it back unchanged.

Overridden shards can span NUMA nodes, so scx_shard_node[] is rebuilt by
majority count: each shard is assigned to the node that owns the most cpus
in it.

v2: Snapshot the caller's cpu_to_cid/shard_start arrays before validating. (sashiko AI)

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

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This commit is contained in:

Tejun Heo 2026-07-13 22:18:42 -10:00

parent e2c841b91b

commit 30067643bc

5 changed files with 187 additions and 29 deletions

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154

kernel/sched/ext/cid.c

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11

tools/sched_ext/include/scx/compat.bpf.h

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16

tools/sched_ext/scx_qmap.bpf.c

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34

tools/sched_ext/scx_qmap.c

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1

tools/sched_ext/scx_qmap.h

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