[Intel-wired-lan] [PATCH] igb: Enable RSS for i211 adapter

Fujinaka, Todd todd.fujinaka at intel.com
Fri Dec 18 14:33:51 UTC 2015


I don’t understand “most defective a bug”. It is a bug.

Most people don’t care too much about using two queues on a controller with only one PCIe lane at 2.5GT/s because the PCIe bus is the bottleneck in this case. In our testing we found that two queues makes little difference in performance and that’s why in our older single-lane 2.5GT/s cards.

We understand that there are more uses for more queues than performance, so we will be fixing this.

Todd Fujinaka
Software Application Engineer
Networking Division (ND)
Intel Corporation
todd.fujinaka at intel.com
(503) 712-4565

From: Tal Abudi [mailto:talabudi at gmail.com]
Sent: Friday, December 18, 2015 1:49 AM
To: Fujinaka, Todd
Cc: Alex Duyck; intel-wired-lan at lists.osuosl.org; alexander.duyck at gmail.com
Subject: Re: [Intel-wired-lan] [PATCH] igb: Enable RSS for i211 adapter

The I211 supports only 2 queues according to the datasheet.
Is there a real difference between E1000_MRQC_ENABLE_RSS_4Q and E1000_MRQC_ENABLE_RSS_8Q ?
The number of the rss is set inside the adapter and the netdevice's dev.
And we can see in igb_init_queue_configuration() that max_rss_queues = IGB_MAX_RX_QUEUES_I211 (2).

I tested 5.3.2 with this patch on a 2 core system and packets distributed evenly among queues.

This is most defective a bug, right ?

On Thu, Dec 17, 2015 at 8:52 PM, Fujinaka, Todd <todd.fujinaka at intel.com<mailto:todd.fujinaka at intel.com>> wrote:
As I was composing this email, I noticed the same thing. I'll double-check to make sure the comment is actually necessary.

Thanks Alex!

Todd Fujinaka
Software Application Engineer
Networking Division (ND)
Intel Corporation
todd.fujinaka at intel.com<mailto:todd.fujinaka at intel.com>
(503) 712-4565<tel:%28503%29%20712-4565>


-----Original Message-----
From: Alex Duyck [mailto:aduyck at mirantis.com<mailto:aduyck at mirantis.com>]
Sent: Thursday, December 17, 2015 10:43 AM
To: Fujinaka, Todd
Cc: intel-wired-lan at lists.osuosl.org<mailto:intel-wired-lan at lists.osuosl.org>; alexander.duyck at gmail.com<mailto:alexander.duyck at gmail.com>; Tal Abudi
Subject: Re: [Intel-wired-lan] [PATCH] igb: Enable RSS for i211 adapter

On Thu, Dec 17, 2015 at 10:37 AM, Fujinaka, Todd <todd.fujinaka at intel.com<mailto:todd.fujinaka at intel.com>> wrote:
> I've spent too much time looking into this. I think this was added when someone looked for the register value and it was the same as E1000_MRQC_ENABLE_RSS_8Q and disabled i211 because it doesn't have 8 queues.
>
> I've been asked if you could spin this to add a comment that the two values are the same (E1000_MRQC_ENABLE_RSS_8Q and E1000_MRQC_ENABLE_RSS_4Q).

That would be even more confusing since the value that is being used is RSS_4Q so I am not sure where the 8Q comes into play.  I guess at some point it was renamed?  Feel free to modify the code however you want.  I was just going through and trying to figure out the issue that had been reported and I noticed it wasn't getting enabled.  It's fine with me if you drop me as author if you guys rewrite the patch and add a comment.  You could probably just add a Suggested-by credit to the patch you generate.

- Alex



--
Best regards,
Tal Abudi
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