Messages in this thread | | | Date | Tue, 22 Oct 2013 10:55:02 -0600 (MDT) | From | Keith Busch <> | Subject | Re: [PATCH 3/3] NVMe: Convert to blk-mq |
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On Fri, 18 Oct 2013, Matias Bjørling wrote: > On 10/18/2013 05:13 PM, Keith Busch wrote: >> On Fri, 18 Oct 2013, Matias Bjorling wrote: >>> The nvme driver implements itself as a bio-based driver. This primarily >>> because of high lock congestion for high-performance nvm devices. To >>> remove the congestion within the traditional block layer, a multi-queue >>> block layer is being implemented.
>>> - result = nvme_map_bio(nvmeq, iod, bio, dma_dir, psegs); >>> - if (result <= 0) >>> + if (nvme_map_rq(nvmeq, iod, rq, dma_dir)) >>> goto free_cmdid; >>> - length = result; >>> >>> - cmnd->rw.command_id = cmdid; >>> + length = blk_rq_bytes(rq); >>> + >>> + cmnd->rw.command_id = rq->tag; >> >> The command ids have to be unique on a submission queue. Since each >> namespace's blk-mq has its own 'tags' used as command ids here but share >> submission queues, what's stopping the tags for commands sent to namespace >> 1 from clashing with tags for namespace 2? >> >> I think this would work better if one blk-mq was created per device >> rather than namespace. It would fix the tag problem above and save a >> lot of memory potentially wasted on millions of requests allocated that >> can't be used. > > You're right. I didn't see the connection. In v3 I'll push struct > request_queue to nvme_dev and map the queues appropriately. It will also fix > the command id issues.
Just anticipating a possible issue with the suggestion. Will this separate the logical block size from the request_queue? Each namespace can have a different format, so the block size and request_queue can't be tied together like it currently is for this to work. | |