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

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Date:   Wed, 2 Aug 2017 18:39:08 +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 18:10, Måns Rullgård wrote:

> Mason writes:
> 
>> On 02/08/2017 17:56, Måns Rullgård wrote:
>>
>>> What does the tango5 do if you flood it with packets faster than the
>>> kernel can keep up with?  That would make it hit the end of the rx
>>> chain, which is apparently what makes it miserable with the current dma
>>> stop code.
>>
>> The simplest way to test this would be sending tiny packets
>> as fast as possible, right? So ping -f on a GigE link should
>> fit the bill?
> 
> ping -f is limited to 100 packets per second.  Use something like iperf
> in UDP mode instead.

ping -f can go 100 times faster than 100 pps:

# ping -f -q -c 150000 -s 300 172.27.64.45
PING 172.27.64.45 (172.27.64.45) 300(328) bytes of data.

--- 172.27.64.45 ping statistics ---
150000 packets transmitted, 150000 received, 0% packet loss, time 15035ms
rtt min/avg/max/mdev = 0.065/0.084/0.537/0.014 ms, ipg/ewma 0.100/0.087 ms


150,000 packets in 15 seconds = 10,000 pps

(172.27.64.45 is the tango5 board)

Ergo, dealing with 10,000 packets per second does not hose RX.

Regards.