netdev - Re: Synopsys Ethernet QoS

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 13 Dec 2016 13:31:16 +0100
From:   Niklas Cassel <niklas.cassel@...s.com>
To:     Joao Pinto <Joao.Pinto@...opsys.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
CC:     David Miller <davem@...emloft.net>,
        Giuseppe CAVALLARO <peppe.cavallaro@...com>, <larper@...s.com>,
        <rabinv@...s.com>, netdev <netdev@...r.kernel.org>,
        <CARLOS.PALMINHA@...opsys.com>, <Jie.Deng1@...opsys.com>,
        Stephen Warren <swarren@...dia.com>, <pavel@....cz>
Subject: Re: Synopsys Ethernet QoS



On 12/13/2016 12:49 PM, Joao Pinto wrote:
> Hi Niklas,
>
> Às 4:25 PM de 12/12/2016, Niklas Cassel escreveu:
>>
>> On 12/12/2016 11:19 AM, Joao Pinto wrote:
>>> Hi,
>>>
>>> Às 1:44 AM de 12/10/2016, Florian Fainelli escreveu:
>>>> Le 12/09/16 à 16:16, Andy Shevchenko a écrit :
>>>>> On Sat, Dec 10, 2016 at 12:52 AM, Florian Fainelli <f.fainelli@...il.com> wrote:
> (snip...)
>
>
>>> @Rabin Vincent: Hi Rabin. Since Axis is more familiar with the synopsys/*qos*
>>> driver would it be possible for you to make an initial analysis of what has to
>>> be merged into Stmmac? This way the development would speed-up.
>> I can answer that question.
>>
>> I've sent out 12 patches to the stmmac driver
>> (all patches are included in the current net-next tree),
>> with these patches the stmmac driver works properly on Axis hardware
>> (we use Synopsys GMAC 4.10a synthesized with multiple TX queues).
>> stmmac's DT binding has also been extended with properties that
>> existed in DWC EQoS's DT binding, such as no-pbl-x8, txpbl, rxpbl.
>>
>> Since we have no problem updating the DTB together with the kernel,
>> we will simply move to using the start using the stmmac driver,
>> with stmmac's DT binding.
>>
>> However, I've noticed that NVIDIA has extended the DWC EQoS DT binding,
>> I don't how easy it would be for them to switch to stmmac's DT binding.
>> (Adding Stephen Warren to CC.)
>>
>> The reset sequence that Lars Persson was worried about is not an issue
>> with the stmmac driver.
> Great! So you saying that stmmac works great with AXIS hardware and no need to
> merge specific code from AXIS' *qos* driver?

Yes. From Axis point of view, we are done.
stmmac works and we will move to that driver + DT binding.

However, it seems like Stephen Warren will NAK if you try to remove
synopsys/dwc_eth_qos.c before
Documentation/devicetree/bindings/net/stmmac.txt
is compatible with
Documentation/devicetree/bindings/net/snps,dwc-qos-ethernet.txt

You might want to sync with him. I have no idea, but perhaps they are
only using a subset of all the available properties. Perhaps,
only implementing what they are using might be enough, I don't know.
I couldn't find their DTS in arch/arm/dts.
I guess you might want to know David Miller's opinion,
since he's the one who decides in the end.

>>
>>
>>
>> There are some performance problems with the stmmac driver though:
>>
>> When running iperf3 with 3 streams:
>> iperf3 -c 192.168.0.90 -P 3 -t 30
>> iperf3 -c 192.168.0.90 -P 3 -t 30 -R
>>
>> I get really bad fairness between the streams.
>>
>> This appears to be an issue with how TX IRQ coalescing is implemented in stmmac.
>> Disabling TX IRQ coalescing in the stmmac driver makes the problem go away.
>> We have a local patch that implements TX IRQ coalescing in the dwceqos driver,
>> and we don't see the same problem.
>>
>> Also netperf TCP_RR and UDP_RR gives really bad results compared to the
>> dwceqos driver (without IRQ coalescing).
>> 2000 transactions/sec vs 9000 transactions/sec.
>> Turning TX IRQ coalescing off and RX interrupt watchdog off in stmmac
>> gives the same performance. I guess it's a trade off, low CPU usage
>> vs low latency, so I don't know how important TCP_RR/UDP_RR really is.
>>
>> The best thing would be to get a good working TX IRQ coalesce
>> implementation with HR timers in stmmac.
>> Perhaps it should also be investigated if the RX interrupt watchdog
>> timeout should have a lower default value.
>>
>>
>>
>>> Thanks to all.
>>>
>>> Joao