Intel 82574L (em)

[Sean Bruno]

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On 02/10/15 18:49, Sepherosa Ziehau wrote:
> On Sat, Jan 31, 2015 at 5:11 AM, Sean Bruno
> <sbruno at ignoranthack.me> wrote:
>> 
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>> 
>> http://www.intel.com/content/dam/doc/datasheet/82574l-gbe-controller-datasheet.pdf
>>
>>
>> 
According to 7.1.11, this device does indeed have 2 queues for stuff and
>> or things.  So, basic RSS would be possible in something like an
>> Atom box.
>> 
>> I note that the em(4) driver intentionally disables this on 
>> initialization.  I'm up for some science on my new shiny, soon to
>> be router box. Any reason not to default to 1 queue and allow
>> loader.conf to raise it to 2?
> 
> You could actually enable 2 RX rings w/o MSI-X on 82574; you still
> get the benefit of hardware calculated RSS hash at least.  And as
> far as I have tested, 2 RX rings work for 82574L, but 2 TX rings
> don't work (gave me TX watchdog timeout).  And you could also use 2
> RX rings on 82571/82572/82573 and i217/i218; 2 TX rings work on
> 82571 at least (you need to setup TX context for each TX descriptor
> though).
> 
> Best Regards, sephe
> 
> 


I'm interested in doing this a bit as I now have 5 em(4) interfaces on
my soon to be router box.

I tried modifying the driver to allow num_queues to be raised and I
compiled with EM_MULTIQUEUE set, and all I got for my trouble was
kernel panics.

I'm not sure if the code even works.

sean
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