Sorry for the further delay, On Wed, 14 Dec 2022 11:35:46 +0100 Stefano Brivio <sbrivio(a)redhat.com> wrote:On Wed, 14 Dec 2022 12:42:14 +1100 David Gibson <david(a)gibson.dropbear.id.au> wrote:I was checking the wrong path. With this: -- diff --git a/test/perf/pasta_udp b/test/perf/pasta_udp index 27ea724..973c2f4 100644 --- a/test/perf/pasta_udp +++ b/test/perf/pasta_udp @@ -31,6 +31,14 @@ report pasta lo_udp 1 __FREQ__ th MTU 1500B 4000B 16384B 65535B +tr UDP throughput over IPv6: host to ns +nsout IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname' +nsout ADDR6 ip -j -6 addr show|jq -rM '.[] | select(.ifname == "__IFNAME__").addr_info[] | select(.scope == "global" and .prefixlen == 64).local' +bw - +bw - +bw - +iperf3 BW host ns __ADDR6__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 15G +bw __BW__ 7.0 9.0 tr UDP throughput over IPv6: ns to host ns ip link set dev lo mtu 1500 diff --git a/test/run b/test/run index e07513f..b53182b 100755 --- a/test/run +++ b/test/run @@ -67,6 +67,14 @@ run() { test build/clang_tidy teardown build + VALGRIND=0 + setup passt_in_ns + test passt/ndp + test passt/dhcp + test perf/pasta_udp + test passt_in_ns/shutdown + teardown passt_in_ns + setup pasta test pasta/ndp test pasta/dhcp -- I get 21.6 gbps after this series, and 29.7 gbps before -- it's quite significant. And there's nothing strange in perf's output, really, the distribution of overhead per functions is pretty much the same, but writing multiple messages to the tap device just takes more cycles per message compared to a single message. I'm a bit ashamed to propose this, but do you think about something like: if (c->mode == MODE_PASTA) { if (recvmmsg(ref.r.s, mmh_recv, 1, 0, NULL) <= 0) return; if (udp_mmh_splice_port(v6, mmh_recv)) { n = recvmmsg(ref.r.s, mmh_recv + 1, UDP_MAX_FRAMES - 1, 0, NULL); } if (n > 0) n++; else n = 1; } else { n = recvmmsg(ref.r.s, mmh_recv, UDP_MAX_FRAMES, 0, NULL); if (n <= 0) return; } ? Other than the inherent ugliness, it looks like a good approximation to me. -- StefanoOn Tue, Dec 13, 2022 at 11:48:47PM +0100, Stefano Brivio wrote:Oh, right, I see. Then let me add this path to the perf/pasta_udp test and check how relevant this is now, I'll get back to you in a bit.Sorry for the long delay here, On Mon, 5 Dec 2022 19:14:21 +1100 David Gibson <david(a)gibson.dropbear.id.au> wrote:Hm, ok.Usually udp_sock_handler() will receive and forward multiple (up to 32) datagrams in udp_sock_handler(), then forward them all to the tap interface. For unclear reasons, though, when in pasta mode we will only receive and forward a single datagram at a time. Change it to receive multiple datagrams at once, like the other paths.This is explained in the commit message of 6c931118643c ("tcp, udp: Receive batching doesn't pay off when writing single frames to tap"). I think it's worth re-checking the throughput now as this path is a bit different, but unfortunately I didn't include this in the "perf" tests :( because at the time I introduced those I wasn't sure it even made sense to have traffic from the same host being directed to the tap device. The iperf3 runs were I observed this are actually the ones from the Podman demo. Ideally that case should be also checked in the perf/pasta_udp tests.How fundamental is this for the rest of the series? I couldn't find any actual dependency on this but I might be missing something.So the issue is that prior to this change in pasta we receive multiple frames at once on the splice path, but one frame at a time on the tap path. By the end of this series we can't do that any more, because we don't know before the recvmmsg() which one we'll be doing.