Messages in this thread | | | Date | Thu, 2 Dec 2021 15:48:14 +0000 | Subject | Re: [RFC 00/12] io_uring zerocopy send | From | Pavel Begunkov <> |
| |
On 12/1/21 21:51, Martin KaFai Lau wrote: > On Wed, Dec 01, 2021 at 08:15:28PM +0000, Pavel Begunkov wrote: >> On 12/1/21 19:20, David Ahern wrote: >>> On 12/1/21 12:11 PM, Pavel Begunkov wrote: >>>> btw, why a dummy device would ever go through loopback? It doesn't >>>> seem to make sense, though may be missing something. >>> >>> You are sending to a local ip address, so the fib_lookup returns >>> RTN_LOCAL. The code makes dev_out the loopback: >>> >>> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/net/ipv4/route.c#n2773 >> >> I see, thanks. I still don't use the skb_orphan_frags_rx() hack >> and it doesn't go through the loopback (for my dummy tests), just >> dummy_xmit() and no mention of loopback in perf data, see the >> flamegraph. Don't know what is the catch. >> >> I'm illiterate of the routing paths. Can it be related to >> the "ip route add"? How do you get an ipv4 address for the device? > I also bumped into the udp-connect() => ECONNREFUSED (111) error from send-zc. > because I assumed no server is needed by using dummy. Then realized > the cover letter mentioned msg_zerocopy is used as the server. > Mentioning just in case someone hits it also. > > To tx out dummy, I did: > #> ip a add 10.0.0.1/24 dev dummy0
Works well for me, IOW getting the same behaviour as with my ip route add <ip> dev dummy0
I'm curious what is the difference bw them?
> #> ip -4 r > 10.0.0.0/24 dev dummy0 proto kernel scope link src 10.0.0.1 > > #> ./send-zc -4 -D 10.0.0.(2) -t 10 udp > ip -s link show dev dummy0 > 2: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 65535 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 > link/ether 82:0f:e0:dc:f7:e6 brd ff:ff:ff:ff:ff:ff > RX: bytes packets errors dropped missed mcast > 0 0 0 0 0 0 > TX: bytes packets errors dropped carrier collsns > 140800890299 2150397 0 0 0 0 >
-- Pavel Begunkov
| |