From: Hannes Reinecke <hare@suse.de>
To: Christoph Hellwig <hch@lst.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
Linux Kernel Mailinglist <linux-kernel@vger.kernel.org>,
Hannes Reinecke <hare@suse.com>
Subject: Re: [RFC PATCH] pci: add pci_irq_get_affinity_vector()
Date: Tue, 8 Nov 2016 16:08:51 +0100 [thread overview]
Message-ID: <40d6e3d4-7e63-0d23-3e5c-a877cebd539a@suse.de> (raw)
In-Reply-To: <20161108145652.GA12817@lst.de>
On 11/08/2016 03:56 PM, Christoph Hellwig wrote:
> On Tue, Nov 08, 2016 at 08:47:21AM +0100, Hannes Reinecke wrote:
>> Add a reverse-mapping function to return the interrupt vector for
>> any CPU if interrupt affinity is enabled.
>
> What's the use case of it?
>
> Also as-is this won't work due to the non-affinity vectors that
> have the affinity set to all cpus. It will get even worse if we have
> to support things like virtio_net that have multiple interrupts per
> CPU due to the send and receive virtqueues.
>
The use-case here is that one needs to feed the MSI-X index into the
driver command structure. While we can extract that number trivially
with scsi-mq, but for scsi-sq we don't have such means.
So if we start assigning interrupt affinity per default we need to
figure out the msi-x index from a given SCSI command.
Currently most of these drivers keep an internal CPU map which I'd love
to get rid of.
Hence this patch.
And before you complain: Yes, this patch is wrong; it returns the vector
and not the index (which is what I'm after).
I found that on my test machine :-(
The main impetus of this RFC is to figure out if such a function would
have a chance of getting upstream, or if I have to continue use cpumaps
in the drivers.
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@suse.de +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
next prev parent reply other threads:[~2016-11-08 15:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-08 7:47 [RFC PATCH] pci: add pci_irq_get_affinity_vector() Hannes Reinecke
2016-11-08 14:48 ` Thomas Gleixner
2016-11-08 14:56 ` Christoph Hellwig
2016-11-08 15:08 ` Hannes Reinecke [this message]
2016-11-08 15:11 ` Christoph Hellwig
2016-11-08 15:20 ` Hannes Reinecke
2016-11-08 15:25 ` Christoph Hellwig
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