Re: [Qemu-devel] [PATCH 12/12] nbd: split requests

[Paolo Bonzini]

On 09/09/2011 04:52 PM, Nicholas Thomas wrote:
> > >  +/* qemu-nbd has a limit of slightly less than 1M per request.  For safety,
> > >  + * transfer at most 512K per request. */
> > >  +#define NBD_MAX_SECTORS 1024
>
> As far as I'm aware, the limit of 1MiB - header size is common to all
> NBD servers. I'm not aware of anything at all that'll fail on a 768K
> request but succeed in the exact same circumstances on a 512K request.
> Again, this is a performance consideration - each request is relatively
> slow, so you don't want them to be unnecessarily small.

Yes, it should probably be bumped to 1536 or 2040 (to keep requests 
4k-aligned).  I wasn't sure about the limit.  I've never seen requests 
that big anyway.

Paolo