linux-kernel - Re: [PATCH 0/9] staging: octeon: multi rx group (queue) support

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Date:   Wed, 31 Aug 2016 09:10:02 -0700
From:   David Daney <ddaney@...iumnetworks.com>
To:     Aaro Koskinen <aaro.koskinen@....fi>
CC:     Ed Swierk <eswierk@...portsystems.com>,
        driverdev-devel <devel@...verdev.osuosl.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/9] staging: octeon: multi rx group (queue) support

On 08/31/2016 08:06 AM, Aaro Koskinen wrote:
> Hi,
>
> On Tue, Aug 30, 2016 at 06:12:17PM -0700, Ed Swierk wrote:
>> On Tue, Aug 30, 2016 at 11:47 AM, Aaro Koskinen <aaro.koskinen@....fi> wrote:
>>> This series implements multiple RX group support that should improve
>>> the networking performance on multi-core OCTEONs. Basically we register
>>> IRQ and NAPI for each group, and ask the HW to select the group for
>>> the incoming packets based on hash.
>>>
>>> Tested on EdgeRouter Lite with a simple forwarding test using two flows
>>> and 16 RX groups distributed between two cores - the routing throughput
>>> is roughly doubled.
>>
>> I applied the series to my 4.4.19 tree, which involved backporting a
>> bunch of other patches from master, most of them trivial.
>>
>> When I test it on a Cavium Octeon 2 (CN6880) board, I get an immediate
>> crash (bus error) in the netif_receive_skb() call from cvm_oct_poll().
>> Replacing the rx_group argument to cvm_oct_poll() with int group, and
>> dereferencing rx_group->group in the caller (cvm_oct_napi_poll())
>> instead makes the crash disappear. Apparently there's some race in
>> dereferencing rx_group from within cvm_oct_poll().
>>
>> With this workaround in place, I can send and receive on XAUI
>> interfaces, but don't see any performance improvement. I'm guessing I
>> need to set receive_group_order > 0. But any value between 1 and 4
>> seems to break rx altogether. When I ping another host I see both
>> request and response on the wire, and the interface counters increase,
>> but the response doesn't make it back to ping.
>
> This happens only on CN68XX, and I found the root cause.
>
> I will send a new series later today.

Thanks,

cn68xx does have a slightly different SSO and interrupt implementation, 
so it will probably need some special case code to handle both styles of 
hardware.

David.

>
> A.
>