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Date: Mon, 21 Dec 2020 11:58:14 +0100 From: Eric Dumazet <edumazet@...gle.com> To: Rainer Suhm <automat@...teo.de> Cc: "David S. Miller" <davem@...emloft.net>, netdev <netdev@...r.kernel.org> Subject: Re: PROBLEM: Poor wlan performance with lots of retries since kernel 5.9 On Mon, Dec 21, 2020 at 12:19 AM Rainer Suhm <automat@...teo.de> wrote: > > Since kernel 5.9 I do have very poor wlan performance with one of my machines. > The transmission rate is only about a tenth of normal speed (~60MB/s -> 6 MB/s). > iperf3 -c <server> shows hundreds of retries per second > --- snip --- > [ ID] Interval Transfer Bitrate Retr Cwnd > [ 5] 0.00-1.00 sec 8.55 MBytes 71.7 Mbits/sec 649 1.41 KBytes > [ 5] 1.00-2.00 sec 5.78 MBytes 48.5 Mbits/sec 366 17.0 KBytes > [ 5] 2.00-3.00 sec 5.97 MBytes 50.0 Mbits/sec 371 19.8 KBytes > [ 5] 3.00-4.00 sec 5.84 MBytes 49.0 Mbits/sec 390 17.0 KBytes > [ 5] 4.00-5.00 sec 6.21 MBytes 52.1 Mbits/sec 380 19.8 KBytes > [ 5] 5.00-6.00 sec 4.54 MBytes 38.1 Mbits/sec 299 1.41 KBytes > [ 5] 6.00-7.00 sec 6.34 MBytes 53.2 Mbits/sec 367 26.9 KBytes > [ 5] 7.00-8.00 sec 6.15 MBytes 51.6 Mbits/sec 390 19.8 KBytes > [ 5] 8.00-9.00 sec 5.65 MBytes 47.4 Mbits/sec 370 2.83 KBytes > [ 5] 9.00-10.00 sec 5.78 MBytes 48.5 Mbits/sec 377 21.2 KBytes > - - - - - - - - - - - - - - - - - - - - - - - - - > [ ID] Interval Transfer Bitrate Retr > [ 5] 0.00-10.00 sec 60.8 MBytes 51.0 Mbits/sec 3959 sender > [ 5] 0.00-10.00 sec 60.1 MBytes 50.4 Mbits/sec receiver > --- snap --- > (this measurement was taken after booting from the current official arch iso) > > The problem is only when transmitting data. Receiving (iperf3 -c <server> -R) works ok. > No related errors/warnings in dmesg. > The problem exists since kernel v5.9 up to 10.0.2-rc1 > Using other (older) WiFi firmware doesn't help. > Hardware: TUXEDO InfinityBook S 14 v5/L140CU, > with Intel(R) Wi-Fi 6 AX200 160MHz, REV=0x340 > The machine runs Arch Linux, all updates installed. > On all my other laptops this problem doesn't show up. > > > Bisecting leads to: > --- snip --- > 3d5b459ba0e3788ab471e8cb98eee89964a9c5e8 is the first bad commit > commit 3d5b459ba0e3788ab471e8cb98eee89964a9c5e8 > Author: Eric Dumazet <edumazet@...gle.com> > Date: Wed Jun 17 20:53:26 2020 -0700 > > net: tso: add UDP segmentation support > > Note that like TCP, we do not support additional encapsulations, > and that checksums must be offloaded to the NIC. > > Signed-off-by: Eric Dumazet <edumazet@...gle.com> > Signed-off-by: David S. Miller <davem@...emloft.net> > > net/core/tso.c | 29 ++++++++++++++++++----------- > 1 file changed, 18 insertions(+), 11 deletions(-) > --- snap --- > > After reverting e89964a9c5e8, everything seems ok. WLan works with expected speed, and iperf3 doesn't show retries any more. > I confirm this for kernels 5.10.1 and 5.10.2-rc1 (00017-gc96cfd687a3f). > > If I should provide more information, let me know. > Please note: I'm not on any list. So please make sure to address me explicitly if replying to this mail. > > Thanks for the report. A similar report has been sent a few days ago by Ben Greear, let's keep the discussion there please.
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