I generalize, but this is a problem which affects a few devices in the
DSA bring-up.
Some platforms require some tinkering and tweaking, and perhaps input
from the chip-set manufacturer (or information from a datasheet of the
chip-set) if things are to improve.
DSA brings advantages and is the future: everyone is already committed.
OEMs have been laying low tho and just used older 2.x kernels which the
mfrs provided with the chip-sets originally to avoid this maintenance
themselves if at all possible.
You can have a look at PRs for other platforms and their protracted DSA
bring-ups on github.
e.g. for the qca8k switch chip, some of the lads have been moving mountains:
https://github.com/openwrt/openwrt/pull/4036
https://github.com/openwrt/openwrt/pull/4622
https://github.com/openwrt/openwrt/pull/4828
This will give you an idea of the amount of work which may be necessary
to return performance to 19.x swconfig levels.
I don't dabble in mt7621, so cannot be of help there as to whether there
is something ongoing for those.
On 2021-12-19 12:29, Kristian Evensen wrote:
Hello,
I am currently performing some performance measurements, comparing the
(wired) routing throughput (WAN <-> LAN) of 19.07, 21.02 and master on
mt7621 (ZBT WG-3526). I have connected one client to my LAN and one to
the WAN, and use iperf3 to measure. I create parallel flows (in order
to take advantage of the multiple CPU cores), use TCP and let iperf3
run for 30 sec. per test.
Based on my measurements, the throughput is reduced by ~50% going from
19.07 and to 21.02/master (~450Mbit/s vs. ~900Mbit/s). I do not have a
particular commit I can point to, but I believe the regressions is
caused by the introduction of DSA. Restoring the old swconfig driver,
brings my 21.02/master throughput up to roughly the same level as
19.07.
I am able to alleviate the reduction in throughput by enabling flow
offloading, but there are several cases where flow offloading does not
have an effect. When performing a similar measurement to the one above
over a Wireguard-tunnel, I see a similar reduction in performance (and
no help from flow offloading).
Does anyone know what could be the reason and if there is anything
that can be done to improve the performance when using DSA? Are there
for example any out of tree/not yet accepted patches that I should
try?
Thanks in advance for any help,
Kristian
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