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> > + if (cpumask_subset(llc_cpus, cluster)) > > + return NULL; > > The second drop inverts the hardware on a part whose cores all share one > L2, such as a single E-core module or a DSU whose L2 is the LLC: each core > becomes its own cluster and a scheduler looking for L2 sharers through > cluster_cid finds none. The sched domain doesn't drop the cluster there > either, it drops MC and keeps CLS. Can we make the level inclusive instead > and skip the conditions altogether? > > cpumask_or(cluster_scratch, topology_cluster_cpumask(xcpu), > topology_sibling_cpumask(xcpu)); > cpumask_and(cluster_scratch, cluster_scratch, llc_scratch); Agreed. I'll use the inclusive cluster mask you suggested, so an LLC-wide L2 remains one cluster. > > Private-L2 cores yield the core, modules yield the module and an LLC-wide > L2 yields one cluster per LLC, with the walk order unchanged. That also > drops the helper with its NULL and empty checks, which no arch can > produce, and the lines past 94 columns. > > > + s32 cluster_cid = next_cid, cluster_idx = next_cluster_idx; > > cluster_scratch is always empty when an LLC starts, so the refill block > assigns both before any use. Plain declarations, and the per-LLC > cpumask_clear() is redundant for the same reason. Right. I'll remove the redundant clear an changed both variables to plain declarations. > > A few smaller things: > > - The comments in cid.c and types.h describe SD_CLUSTER and when the sched > domain drops the level. This layer's contract is enough: the > cache-sharing level between the core and the LLC, and a core without one > is its own cluster. The sched domain also doesn't exist with > CONFIG_SCHED_CLUSTER=n while the L2 masks do. > - scx_bpf_cid_override()'s kerneldoc still says core/LLC/node is cleared. > - The test paragraph can be one sentence, and the Based on note under the > separator is moot now that the fix is in for-7.4. Maybe "sched_ext: Add > the cluster level to the cid topology" for the subject; nothing in the > tree uses a cid: prefix. Ack to all of the above, I'll send a v3. Thanks, -Andrea