Den 22-10-2013 18:55, Keith Busch skrev:
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.
If only a couple of different logical sizes are to be expected (1-4), we
can keep a list of already initialized request queues, and use the one
that match an already initialized?
Axboe, do you know of a better solution?
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