netdev - Re: [RFC PATCH v2 0/2] nb8800 suspend/resume support

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Message-ID: <c1aeaa45-de6a-e643-8765-7dad58a8b038@free.fr>
Date:   Thu, 3 Aug 2017 10:34:31 +0200
From:   Mason <slash.tmp@...e.fr>
To:     Mans Rullgard <mans@...sr.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v2 0/2] nb8800 suspend/resume support

On 02/08/2017 22:02, Mason wrote:

> I need to run the test slightly slower, to prevent packet loss
> at the sender.

# iperf3 -c 172.27.64.45 -u -b 0 -l 1000
Connecting to host 172.27.64.45, port 5201
[  4] local 172.27.64.1 port 42607 connected to 172.27.64.45 port 5201
[ ID] Interval           Transfer     Bandwidth       Total Datagrams
[  4]   0.00-1.00   sec   111 MBytes   931 Mbits/sec  116420  
[  4]   1.00-2.00   sec   111 MBytes   931 Mbits/sec  116390  
[  4]   2.00-3.00   sec   111 MBytes   930 Mbits/sec  116220  
[  4]   3.00-4.00   sec   111 MBytes   930 Mbits/sec  116310  
[  4]   4.00-5.00   sec   111 MBytes   931 Mbits/sec  116380  
[  4]   5.00-6.00   sec   111 MBytes   930 Mbits/sec  116280  
[  4]   6.00-7.00   sec   111 MBytes   931 Mbits/sec  116390  
[  4]   7.00-8.00   sec   111 MBytes   931 Mbits/sec  116370  
[  4]   8.00-9.00   sec   111 MBytes   931 Mbits/sec  116340  
[  4]   9.00-10.00  sec   111 MBytes   930 Mbits/sec  116310  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Jitter    Lost/Total Datagrams
[  4]   0.00-10.00  sec  1.08 GBytes   931 Mbits/sec  0.009 ms  278644/1163363 (24%)  
[  4] Sent 1163363 datagrams

iperf Done.


# iperf3 -s
Accepted connection from 172.27.64.1, port 42966
[  5] local 172.27.64.45 port 5201 connected to 172.27.64.1 port 42607
[ ID] Interval           Transfer     Bandwidth       Jitter    Lost/Total Datagrams
[  5]   0.00-1.00   sec  81.1 MBytes   681 Mbits/sec  0.017 ms  26834/111909 (24%)  
[  5]   1.00-2.00   sec  84.2 MBytes   706 Mbits/sec  0.019 ms  28127/116384 (24%)  
[  5]   2.00-3.00   sec  84.2 MBytes   706 Mbits/sec  0.013 ms  27946/116204 (24%)  
[  5]   3.00-4.00   sec  84.5 MBytes   709 Mbits/sec  0.013 ms  27674/116311 (24%)  
[  5]   4.00-5.00   sec  84.6 MBytes   709 Mbits/sec  0.015 ms  27712/116387 (24%)  
[  5]   5.00-6.00   sec  84.5 MBytes   709 Mbits/sec  0.010 ms  27649/116265 (24%)  
[  5]   6.00-7.00   sec  84.3 MBytes   707 Mbits/sec  0.011 ms  27995/116382 (24%)  
[  5]   7.00-8.00   sec  84.3 MBytes   707 Mbits/sec  0.013 ms  27972/116387 (24%)  
[  5]   8.00-9.00   sec  84.3 MBytes   708 Mbits/sec  0.020 ms  27899/116343 (24%)  
[  5]   9.00-10.00  sec  84.4 MBytes   708 Mbits/sec  0.014 ms  27759/116305 (24%)  
[  5]  10.00-10.04  sec  3.25 MBytes   710 Mbits/sec  0.009 ms  1077/4486 (24%)  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Jitter    Lost/Total Datagrams
[  5]   0.00-10.04  sec  0.00 Bytes  0.00 bits/sec  0.009 ms  278644/1163363 (24%)  


IIUC, sender (desktop system) sends datagrams as fast as possible.
Receiver (tango board) drops around 24% of all datagrams.
I think this invalidates the theory that exhausting RX descriptors
wedges RX DMA.

Regards.