sched_ext: Add CID sharding

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Sub-sched operations need a scalable locking / work domain smaller than the
whole cid space. Carve the cid space into topology-respecting shards: each
shard is a contiguous cid range that stays within one LLC, and LLCs larger
than the per-shard cap (default 24 cids, configurable via
ops.cid_shard_size) split into enough shards to fit. A hard cap of
SCX_CID_SHARD_MAX_CPUS prevents pathological sizes under custom
configurations.

No-topo cids pack into their own shards so every cid has a shard assignment.

Also build scx_cid_shard_ranges[] for O(1) shard-to-cid-range lookup and
scx_shard_node[] so callers can size or place work by NUMA without walking
cids. Auto-built shards inherit their LLC's node. No-topo shards carry
NUMA_NO_NODE.

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 874fdc0e86

commit e2c841b91b

5 changed files with 176 additions and 12 deletions

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132

kernel/sched/ext/cid.c

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4

kernel/sched/ext/cid.h

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4

kernel/sched/ext/ext.c

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13

kernel/sched/ext/internal.h

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35

kernel/sched/ext/types.h

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