linux-kernel - Re: [PATCH 2/2] nvme-pci: allow unmanaged interrupts

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Date: Tue, 21 May 2024 10:38:25 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Ming Lei <ming.lei@...hat.com>, Christoph Hellwig <hch@....de>
Cc: Keith Busch <kbusch@...nel.org>, Keith Busch <kbusch@...a.com>,
 linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org, Frederic
 Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH 2/2] nvme-pci: allow unmanaged interrupts

On Tue, May 21 2024 at 10:31, Ming Lei wrote:

> On Mon, May 20, 2024 at 05:37:42PM +0200, Christoph Hellwig wrote:
>> On Sun, May 12, 2024 at 08:35:55AM +0200, Thomas Gleixner wrote:
>> > That's expected as you pin the I/O operation on the isolated CPUs which
>> > in turn makes them use the per CPU queue.
>> > 
>> > The isolated CPUs are only excluded for device management interrupts,
>> > but not for the affinity spread of the queues.
>> 
>> We'll probably need a version of isolcpus that also excludes the
>> interrupt spread given that users are asking for it.  And I'd much
>> prefer that over adding radom module options to every driver to disable
>> managed interrupts.
>
> BTW, isolcpus has been marked as deprecated, and it can't be adjust
> runtime.

Which is far from reality as cpusets do not allow to do what isolcpus
does today.

Also runtime adjusting managed interrupts needs way more thoughts.

Thanks

        tglx