Re: [PATCH] char_dev: replace cdev_map with an xarray

[Greg KH]

On Mon, Jan 11, 2021 at 05:35:00PM +0000, Matthew Wilcox wrote:
> On Mon, Jan 11, 2021 at 06:05:13PM +0100, Christoph Hellwig wrote:
> > None of the complicated overlapping regions bits of the kobj_map are
> > required for the character device lookup, so just a trivial xarray
> > instead.
> 
> Thanks for doing this.  We could make it more efficient for chardevs
> that occupy 64 or more consecutive/aligned devices -- is it worth doing?

efficient in what way?  Space or faster lookup?

THis shouldn't be on a "fast" lookup path, so I doubt that's worth
optimizing for.  Space, maybe, for systems with thousands of scsi
devices, but usually they just stick to the block device, not a char
device from what I remember.

thanks,

greg k-h