sched_ext: Specialize the scheduler hashtable compare

scx_sched_hash_params does not provide an object comparison function,
so rhashtable falls back to rhashtable_compare(). Although the
sub-cgroup ID key is one naturally aligned u64, the generic comparison
reads the key offset and length from the table parameters at runtime and
emits an out-of-line memcmp() for each element walked.

Supply an obj_cmpfn so lookups specialize to a single equality test
against ops.sub_cgroup_id. ext.c and sub.c are included in the same
build_policy.c translation unit, so the compiler can fold the const
callback into scx_find_sub_sched() even though its source is in sub.c.

The result is only tested against zero, so the ordering provided by
memcmp() is not observable. No functional change intended.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Usama Arif <usama.arif@linux.dev>
Signed-off-by: Tejun Heo <tj@kernel.org>

0 files changed, 0 insertions, 0 deletions