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

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Date:	Mon, 28 Mar 2016 11:19:58 -0700
From:	Weongyo Jeong <weongyo.linux@...il.com>
To:	Christoph Hellwig <hch@...radead.org>
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 12:32:43PM -0700, Christoph Hellwig wrote:
> 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.

This could be a silly question.  Are you meaning that we should remove
feature of IRQ affinity notifiers and device writer should explicitly set
CPU affinity with masking when it requests IRQ?

And then some CPU affinity of IRQ are still changable via
/proc/irq/<n>/smp_affinity and some aren't for device drivers, right?

Regards,
Weongyo Jeong