linux-kernel - Re: [PATCH v1 0/2] genirq: support multiple IRQ notifier.

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Date:	Fri, 25 Mar 2016 12:32:43 -0700
From:	Christoph Hellwig <hch@...radead.org>
To:	Weongyo Jeong <weongyo.linux@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
	linux-scsi@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Mike Marciniszyn <infinipath@...el.com>,
	"James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>
Subject: Re: [PATCH v1 0/2] genirq: support multiple IRQ notifier.

On Fri, Mar 25, 2016 at 08:51:51AM -0700, Weongyo Jeong wrote:
> Each irq_desc only supports one IRQ affinity notifier at current
> implementation so when we try to register another notifier, it silently
> unregister previous entry and register new one.
> 
> However the problem is that if CONFIG_RFS_ACCEL is set, at current
> implementation no way to set additional IRQ affinity notifier for
> some NIC cards RFS enabled because it already used for RFS.
> With this patch we can register multiple IRQ affinity notifiers.

The whole concept of these irq affinity notifiers seems wrong to me.

If a device supports MSI-X it should simply request per-cpu or per-node
vectors and we should prevent affinity changes for them.