netdev - Re: [PATCH net-next 0/9] ionic: Add support for Event Queues

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Message-Id: <20200217.140344.810813375227195875.davem@davemloft.net>
Date:   Mon, 17 Feb 2020 14:03:44 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     snelson@...sando.io
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/9] ionic: Add support for Event Queues

From: Shannon Nelson <snelson@...sando.io>
Date: Sun, 16 Feb 2020 22:55:22 -0800

> On 2/16/20 8:11 PM, David Miller wrote:
>> From: Shannon Nelson <snelson@...sando.io>
>> Date: Sun, 16 Feb 2020 15:11:49 -0800
>>
>>> This patchset adds a new EventQueue feature that can be used
>>> for multiplexing the interrupts if we find that we can't get
>>> enough from the system to support our configuration.  We can
>>> create a small number of EQs that use interrupts, and have
>>> the TxRx queue pairs subscribe to event messages that come
>>> through the EQs, selecting an EQ with (TxIndex % numEqs).
>> How is a user going to be able to figure out how to direct
>> traffic to specific cpus using multiqueue settings if you're
>> going to have the mapping go through this custom muxing
>> afterwards?
> 
> When using the EQ feature, the TxRx are assigned to the EventQueues in
> a straight round-robin, so the layout is predictable.  I suppose we
> could have a way to print out the TxRx -> EQ -> Irq mappings, but I'm
> not sure where we would put such a thing.

No user is going to know this and it's completely inconsistent with how
other multiqueue networking devices behave.