pf: add pf_bcmp_state_key

[mjg]

Summary

The comparison size of 40 bytes is known at compilation time but clang refuses to optimize it, thus hand-roll a short variant.

Benchmarked on a kernel with other changes on top of it. Interestingly it fails to provide a speed up, but instead it shifts CPU time elsewhere.

before: https://people.freebsd.org/~mjg/pf_nohashrow.svg
after: https://people.freebsd.org/~mjg/pf_nohashrow_custom_bcmp.svg

You can see time in netisr_dispatch -> ip_input -> ip_tryforward drop from 12.19 to 10.40 of the total.

[kp]

sys/netpfil/pf/pf.c

431

s1ptr (and s2ptr) is not declared anywhere. Do you mean var1 = k1[0]?

433

Can't we do if (k1[0] != k2[0])?

[mjg]

• drop the temp var

[mjg]

sys/netpfil/pf/pf.c

431

i somehow upload the older version

[kp]

There's one more in sys/netpfil/pf/pf_lb.c that could also use pf_bcmp_state_key() (in pf_get_translation()).