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

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Message-ID: <yw1xfud9hqee.fsf@mansr.com>
Date:   Wed, 02 Aug 2017 17:43:05 +0100
From:   Måns Rullgård <mans@...sr.com>
To:     Mason <slash.tmp@...e.fr>
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

Mason <slash.tmp@...e.fr> writes:

> 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.

ping -f goes as fast as the other end replies or 100 per second,
whichever is higher, so says the man page.

-- 
Måns Rullgård