sched_ext: Specialize the TID hashtable compare

scx_tid_hash_params does not provide an object comparison function, so
rhashtable falls back to rhashtable_compare(). Although the 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.

scx_bpf_tid_to_task() can sit on hot scheduling paths. Supply an
obj_cmpfn so the const parameters passed into the inlined rhashtable
lookup specialize the comparison to a single equality test against
scx->tid.

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