When there is only tiny amount of TCP connections and the host is slow, e.g. in VM, holding too much TCP segments in an LRO entry will cause RX performance degradation. We now allow network drivers to configure how deep one LRO entry should be.
https://reviews.freebsd.org/D4824 has a disabled network driver usage example.
Reviewed by: Hongjiang Zhang <honzhan microsoft com>, Dexuan Cui <decui microsoft com>, Jun Su <junsu microsoft com>
Tested by: me (local), Hongjiang Zhang <honzhan microsoft com> (directly connected 40Ge)
Sponsored by: Microsoft OSTC
BTW, I think some drivers already put a limit on the # of drivers holding TCP segments, e.g. oce(4), though oce(4) does not use per-LRO entry depth.