From: Tom Herbert <t...@herbertland.com> Date: Wed, 6 Apr 2016 14:42:26 -0300
> On Wed, Apr 6, 2016 at 12:43 PM, David Miller <da...@davemloft.net> wrote: >> From: Tom Herbert <t...@herbertland.com> >> Date: Wed, 6 Apr 2016 10:53:52 -0300 >> >>> Packets that are forwarded really should not be GRO'ed in the first >>> place because of the loss of information and added latency. >> >> First of all GRO is supposed to be lossless, so please stop saying this >> would be a reason to turn it off on a router. >> >> Second of all, the biggest piece of overhead is the routing lookup, >> therefore GRO batching helps enormously with routing workloads, and >> therefore is appropriate to be enabled on routers. >> >> Yes, I agree that for locally terminated stuff it helps more, but don't >> turn this into a "GRO on routers, meh..." type argument. It simply is >> not true at all. >> > GRO on routers will help in a limited case where there is little load > and the traffic is nicely groomed high tput TCP connections. But for > routers with significant load, handling large quantities other > protocols like UDP, GRO is not necessarily helpful and presents a > nondeterministic performance improvement. For instance, I cannot > provision a router with any assumptions that GRO will be effective for > any % of packets to save any % of CPU, we need to provision based > purely on ability to forward by pps assuming no benefit from GRO. Just because you cannot predict how effective a facility will be, that doesn't mean you shouldn't use it at all.
