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From: Ming Lei <ming.lei@redhat.com>
To: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>,
	John Garry <john.garry@huawei.com>, Jens Axboe <axboe@kernel.dk>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-scsi@vger.kernel.org, Sagi Grimberg <sagi@grimberg.me>,
	Daniel Wagner <dwagner@suse.de>, Wen Xiong <wenxiong@us.ibm.com>,
	Keith Busch <kbusch@kernel.org>,
	Damien Le Moal <damien.lemoal@wdc.com>
Subject: Re: [PATCH V2 3/6] scsi: add flag of .use_managed_irq to 'struct Scsi_Host'
Date: Wed, 7 Jul 2021 18:53:02 +0800	[thread overview]
Message-ID: <YOWHjn7S4Otbs93U@T590> (raw)
In-Reply-To: <fb71bccf-0d92-68ed-ad42-cac23fede5a8@suse.de>

On Tue, Jul 06, 2021 at 12:32:27PM +0200, Hannes Reinecke wrote:
> On 7/6/21 9:41 AM, Ming Lei wrote:
> > On Tue, Jul 06, 2021 at 07:37:19AM +0200, Christoph Hellwig wrote:
> > > On Mon, Jul 05, 2021 at 05:55:49PM +0800, Ming Lei wrote:
> > > > The thing is that blk_mq_pci_map_queues() is allowed to be called for
> > > > non-managed irqs. Also some managed irq consumers don't use blk_mq_pci_map_queues().
> > > > 
> > > > So this way just provides hint about managed irq uses, but we really
> > > > need to get this flag set if driver uses managed irq.
> > > 
> > > blk_mq_pci_map_queues is absolutely intended to only be used by
> > > managed irqs.  I wonder if we can enforce that somehow?
> > 
> > It may break some scsi drivers.
> > 
> > And blk_mq_pci_map_queues() just calls pci_irq_get_affinity() to
> > retrieve the irq's affinity, and the irq can be one non-managed irq,
> > which affinity is set via either irq_set_affinity_hint() from kernel
> > or /proc/irq/.
> > 
> But that's static, right? IE blk_mq_pci_map_queues() will be called once
> during module init; so what happens if the user changes the mapping later
> on? How will that be transferred to the driver?

Yeah, that may not work well enough, but still works since non-managed
irq supports migration.

And there are several SCSI drivers which provide module parameter to
enable/disable managed irq, meantime blk_mq_pci_map_queues() is always
called for mapping queues.


Thanks,
Ming


WARNING: multiple messages have this Message-ID (diff)
From: Ming Lei <ming.lei@redhat.com>
To: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>,
	John Garry <john.garry@huawei.com>, Jens Axboe <axboe@kernel.dk>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-scsi@vger.kernel.org, Sagi Grimberg <sagi@grimberg.me>,
	Daniel Wagner <dwagner@suse.de>, Wen Xiong <wenxiong@us.ibm.com>,
	Keith Busch <kbusch@kernel.org>,
	Damien Le Moal <damien.lemoal@wdc.com>
Subject: Re: [PATCH V2 3/6] scsi: add flag of .use_managed_irq to 'struct Scsi_Host'
Date: Wed, 7 Jul 2021 18:53:02 +0800	[thread overview]
Message-ID: <YOWHjn7S4Otbs93U@T590> (raw)
In-Reply-To: <fb71bccf-0d92-68ed-ad42-cac23fede5a8@suse.de>

On Tue, Jul 06, 2021 at 12:32:27PM +0200, Hannes Reinecke wrote:
> On 7/6/21 9:41 AM, Ming Lei wrote:
> > On Tue, Jul 06, 2021 at 07:37:19AM +0200, Christoph Hellwig wrote:
> > > On Mon, Jul 05, 2021 at 05:55:49PM +0800, Ming Lei wrote:
> > > > The thing is that blk_mq_pci_map_queues() is allowed to be called for
> > > > non-managed irqs. Also some managed irq consumers don't use blk_mq_pci_map_queues().
> > > > 
> > > > So this way just provides hint about managed irq uses, but we really
> > > > need to get this flag set if driver uses managed irq.
> > > 
> > > blk_mq_pci_map_queues is absolutely intended to only be used by
> > > managed irqs.  I wonder if we can enforce that somehow?
> > 
> > It may break some scsi drivers.
> > 
> > And blk_mq_pci_map_queues() just calls pci_irq_get_affinity() to
> > retrieve the irq's affinity, and the irq can be one non-managed irq,
> > which affinity is set via either irq_set_affinity_hint() from kernel
> > or /proc/irq/.
> > 
> But that's static, right? IE blk_mq_pci_map_queues() will be called once
> during module init; so what happens if the user changes the mapping later
> on? How will that be transferred to the driver?

Yeah, that may not work well enough, but still works since non-managed
irq supports migration.

And there are several SCSI drivers which provide module parameter to
enable/disable managed irq, meantime blk_mq_pci_map_queues() is always
called for mapping queues.


Thanks,
Ming


_______________________________________________
Linux-nvme mailing list
Linux-nvme@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-nvme

  reply	other threads:[~2021-07-07 10:53 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-02 15:05 [PATCH V2 0/6] blk-mq: fix blk_mq_alloc_request_hctx Ming Lei
2021-07-02 15:05 ` Ming Lei
2021-07-02 15:05 ` [PATCH V2 1/6] blk-mq: prepare for not deactivating hctx if managed irq isn't used Ming Lei
2021-07-02 15:05   ` Ming Lei
2021-07-02 15:05 ` [PATCH V2 2/6] nvme: pci: pass BLK_MQ_F_MANAGED_IRQ to blk-mq Ming Lei
2021-07-02 15:05   ` Ming Lei
2021-07-02 15:05 ` [PATCH V2 3/6] scsi: add flag of .use_managed_irq to 'struct Scsi_Host' Ming Lei
2021-07-02 15:05   ` Ming Lei
2021-07-05  9:25   ` John Garry
2021-07-05  9:25     ` John Garry
2021-07-05  9:55     ` Ming Lei
2021-07-05  9:55       ` Ming Lei
2021-07-06  5:37       ` Christoph Hellwig
2021-07-06  5:37         ` Christoph Hellwig
2021-07-06  7:41         ` Ming Lei
2021-07-06  7:41           ` Ming Lei
2021-07-06 10:32           ` Hannes Reinecke
2021-07-06 10:32             ` Hannes Reinecke
2021-07-07 10:53             ` Ming Lei [this message]
2021-07-07 10:53               ` Ming Lei
2021-07-02 15:05 ` [PATCH V2 4/6] scsi: set shost->use_managed_irq if driver uses managed irq Ming Lei
2021-07-02 15:05   ` Ming Lei
2021-07-05  7:35   ` John Garry
2021-07-05  7:35     ` John Garry
2021-07-06  5:38   ` Christoph Hellwig
2021-07-06  5:38     ` Christoph Hellwig
2021-07-02 15:05 ` [PATCH V2 5/6] virtio: add one field into virtio_device for recording if device " Ming Lei
2021-07-02 15:05   ` Ming Lei
2021-07-02 15:05   ` Ming Lei
2021-07-02 15:55   ` Michael S. Tsirkin
2021-07-02 15:55     ` Michael S. Tsirkin
2021-07-02 15:55     ` Michael S. Tsirkin
2021-07-05  2:48     ` Ming Lei
2021-07-05  2:48       ` Ming Lei
2021-07-05  2:48       ` Ming Lei
2021-07-05  3:59   ` Jason Wang
2021-07-05  3:59     ` Jason Wang
2021-07-05  3:59     ` Jason Wang
2021-07-06  5:42   ` Christoph Hellwig
2021-07-06  5:42     ` Christoph Hellwig
2021-07-06  5:42     ` Christoph Hellwig
2021-07-06  7:53     ` Ming Lei
2021-07-06  7:53       ` Ming Lei
2021-07-06  7:53       ` Ming Lei
2021-07-07  9:06     ` Thomas Gleixner
2021-07-07  9:06       ` Thomas Gleixner
2021-07-07  9:06       ` Thomas Gleixner
2021-07-07  9:42       ` Ming Lei
2021-07-07  9:42         ` Ming Lei
2021-07-07  9:42         ` Ming Lei
2021-07-07 14:05         ` Christoph Hellwig
2021-07-07 14:05           ` Christoph Hellwig
2021-07-07 14:05           ` Christoph Hellwig
2021-07-08  6:34           ` Ming Lei
2021-07-08  6:34             ` Ming Lei
2021-07-08  6:34             ` Ming Lei
2021-07-02 15:05 ` [PATCH V2 6/6] blk-mq: don't deactivate hctx if managed irq isn't used Ming Lei
2021-07-02 15:05   ` Ming Lei

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