On Wed, Jun 3, 2015 at 8:03 PM, Nick Fisk <n...@fisk.me.uk> wrote:
>
> Hi All,
>
>
>
> Am I correct in thinking that in latest kernels, now that krbd is supported
> via blk-mq, the maximum queue depth is now 128 and cannot be adjusted
>
>
>
> http://xo4t.mj.am/link/xo4t/jw0u7zr/1/VnVTVD2KMuL7gZiTD1iRXQ/aHR0cHM6Ly9naXRodWIuY29tL3RvcnZhbGRzL2xpbnV4L2Jsb2IvbWFzdGVyL2RyaXZlcnMvYmxvY2svcmJkLmM
>
> 3753: rbd_dev->tag_set.queue_depth = BLKDEV_MAX_RQ;
>
>
>
> blkdev.h
>
> 42: #define BLKDEV_MAX_RQ 128
>
>
>
> This potentially seems a bit low for some use cases if it can’t be adjusted.
Yeah, the default 128 is the same as before but it can't be adjusted
now (or rather it can be, through /sys/block/rbd0/queue/nr_requests,
but not upwards). Given that we only have one queue and that the
conversion to blk-mq was done mostly for maintenance reasons we should
probably look into allowing users to bump it, but it would be great if we
could see some numbers first.
Thanks,
Ilya
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