Re: nbd: please don't spawn 16 threads when nbd is not even in use

[Yu Kuai <yukuai1@huaweicloud.com>]

Hi,

在 2022/11/24 6:01, Pavel Machek 写道:
> Hi!
>
> > > I see this... and it looks like there are 16 workqueues before nbd is
> > > even used. Surely there are better ways to do that?
> >
> > Yes, it would be nice to create a pool of workers that only spawns up
> > threads when actual parallel requests are made.  Are you willing to
> > help write the patch?
>
> I was thinking more "only spawn a workqueue when nbd is opened" or so.
>
> I have 16 of them, and I'm not using nbd. Workqueue per open device is
> okay, current situation... not so much.

You can take a look at this commit:

e2daec488c57 ("nbd: Fix hungtask when nbd_config_put")

Allocation of recv_workq is moved from start device to alloc device to
fix hungtask. You might need to be careful if you want to move this.

Thanks,
Kuai
>        	       	    	  	  	    	     		Pavel