Subject: Re: [PATCH bpf-next] bpf: don't check against device MTU in __bpf_skb_max_len

From: Toke Høiland-Jørgensen <[email-masked]>
Date: Tue, 15 Sep 2020 10:47:36 +0200

[ just jumping in to answer this bit: ]

> Would you happen to know what ebpf startup overhead is?
> How big a problem is having two (or more) back to back tc programs
> instead of one?

With a jit'ed BPF program and the in-kernel dispatcher code (which
avoids indirect calls), it's quite close to a native function call.

> We're running into both verifier performance scaling problems and code
> ownership issues with large programs...
>
> [btw. I understand for XDP we could only use 1 program anyway...]

Working on that! See my talk at LPC:
https://linuxplumbersconf.org/event/7/contributions/671/

Will post a follow-up to the list once the freplace multi-attach series
lands.

-Toke