Re: [PATCH v8 8/8] nbd: add pre_defined_connections module parameter for pre-created devices

在 2026/8/5 20:29, Yang Erkun 写道:

> blk_mq_update_nr_hw_queues() in nbd_start_device() may cause a queue
> freeze.  The previous commit addressed this for newly created nbd
> devices by setting the expected nr_hw_queues in nbd_dev_add().  However,
> when reusing an old inactive nbd device, the queue freeze can still
> occur if the old nbd->tag_set->nr_hw_queues does not match the new
> socket connection count.  Inactive nbd devices can originate from two
> sources: loading the nbd module with nbds_max, which sets the default
> nr_hw_queues to 1, and the netlink method, which sets nr_hw_queues
> according to the expected number of socket connections.  For the first
> case, add a module parameter so the default nr_hw_queues can be
> changed.  Users who know their expected number of connections can then
> prevent queue freezes on pre-created devices via nbds_max.
>
> Before this patchset:
> real    0m2.195s
> user    0m0.005s
> sys     0m0.022s
>
> After this patchset:
> real    0m0.090s
> user    0m0.004s
> sys     0m0.018s
>
> Signed-off-by: Yang Erkun<[email protected]>
> ---
>   drivers/block/nbd.c | 16 +++++++++++++++-
>   1 file changed, 15 insertions(+), 1 deletion(-)
Reviewed-by: Yu Kuai <[email protected]>

-- 
Thanks,
Kuai