Add a SPD cache to speed up lookups.
When large SPDs are used, we face two problems: - too many CPU cycles are spent during the linear searches in the SPD for each packet - too much contention on multi socket systems, since we use a single shared lock. Main changes: - added the sysctl tree 'net.key.spdcache' to control the SPD cache (disabled by default). - cache the sp indexes that are used to perform SP lookups. - use a range of dedicated mutexes to protect the cache lines. Submitted by: Emeric Poupon <firstname.lastname@example.org> Reviewed by: ae Sponsored by: Stormshield Differential Revision: https://reviews.freebsd.org/D15050