Messages in this thread | | | Subject | Re: [PATCH RFC v2 02/24] scsi: allocate separate queue for reserved commands | From | John Garry <> | Date | Tue, 10 Mar 2020 21:08:56 +0000 |
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On 10/03/2020 18:32, Christoph Hellwig wrote: > On Wed, Mar 11, 2020 at 12:25:28AM +0800, John Garry wrote: >> From: Hannes Reinecke <hare@suse.com> >> >> Allocate a separate 'reserved_cmd_q' for sending reserved commands. > > Why? Reserved command specifically are not in any way tied to queues. > . >
So the v1 series used a combination of the sdev queue and the per-host reserved_cmd_q. Back then you questioned using the sdev queue for virtio scsi, and the unconfirmed conclusion was to use a common per-host q. This is the best link I can find now:
https://www.mail-archive.com/linux-scsi@vger.kernel.org/msg83177.html
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>> My implementation actually allows for per-device reserved tags (eg for >> virtio). But some drivers require to use internal commands prior to any >> device setup, so they have to use a separate reserved command queue just to >> be able to allocate tags. > > Why would virtio-scsi need per-device reserved commands? It currently uses > a global mempool to allocate the reset commands. > Oh, I'm perfectly fine with dropping the per-device reserved commands, and use the host-wide queue in general. It turns out most of the drivers use it that way already. Will be doing so for the next iteration.
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Cheers
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