linux-kernel - Re: Affinity managed interrupts vs non-managed interrupts

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Message-ID: <20180911092254.GB10330@lst.de>
Date:   Tue, 11 Sep 2018 11:22:54 +0200
From:   Christoph Hellwig <hch@....de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Kashyap Desai <kashyap.desai@...adcom.com>,
        Ming Lei <tom.leiming@...il.com>,
        Sumit Saxena <sumit.saxena@...adcom.com>,
        Ming Lei <ming.lei@...hat.com>, Christoph Hellwig <hch@....de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Shivasharan Srikanteshwara 
        <shivasharan.srikanteshwara@...adcom.com>,
        linux-block <linux-block@...r.kernel.org>
Subject: Re: Affinity managed interrupts vs non-managed interrupts

On Sat, Sep 01, 2018 at 12:48:46AM +0200, Thomas Gleixner wrote:
> > We want some changes in current API which can allow us to  pass flags
> > (like *local numa affinity*) and cpu-msix mapping are from local numa node
> > + effective cpu are spread across local numa node.
> 
> What you really want is to split the vector space for your device into two
> blocks. One for the regular per cpu queues and the other (16 or how many
> ever) which are managed separately, i.e. spread out evenly. That needs some
> extensions to the core allocation/management code, but that shouldn't be a
> huge problem.

Note that there are some other uses cases for multiple sets of affinity
managed irqs.  Various network devices insist on having separate TX vs
RX interrupts for example.