netdev - Re: [PATCH net V1 1/3] net/mlx4_en: Don't use irq_affinity_notifier to track changes in IRQ affinity map

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Date:	Tue, 1 Jul 2014 12:14:29 +0300
From:	Amir Vadai <amirv@...lanox.com>
To:	David Miller <davem@...emloft.net>, <amirv.mellanox@...il.com>
CC:	<eric.dumazet@...il.com>, <netdev@...r.kernel.org>,
	<ogerlitz@...lanox.com>, <yevgenyp@...lanox.com>,
	<tglx@...utronix.de>, <ben@...adent.org.uk>, <amira@...lanox.com>,
	<yuvala@...lanox.com>
Subject: Re: [PATCH net V1 1/3] net/mlx4_en: Don't use irq_affinity_notifier
 to track changes in IRQ affinity map

On 07/01/2014 06:33 AM, David Miller wrote:
> From: Amir Vadai <amirv.mellanox@...il.com>
> Date: Mon, 30 Jun 2014 11:34:22 +0300
>
>> On 6/30/2014 9:41 AM, Eric Dumazet wrote:
>>> You might want to drain whole queue instead of limiting to a 'budget',
>>> otherwise, a cpu might be stuck servicing (soft)irq for the TX
>>> completion, even if irq affinities say otherwise.
>>>
>>
>> TX completions are very quick compared to the skb preparation and
>> sending. Which is not the case for RX completions. Because of that, it
>> is very easy to reproduce the problem in RX flows, but we never had any
>> report of that problem in the TX flow.
>> I prefer not to spend time on the TX, since we plan to send a patch soon
>> to use the same NAPI for both TX and RX.
>
> It is always advised to completely ignore the budget for TX work, this is
> what we tell every driver author when discussion NAPI implementations.
>
> Please make your driver conform to this, thanks.
>

Ok.

Please continue the process on this V1 of the patchset. The fix to TX 
poll is not related to this patch - this patch is fixing a regression 
that broke aRFS in mlx4_en.

I will send a separate fix to purge all packets on TX work later on this 
week.

Thanks,
Amir
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