Re: [Qemu-devel] [Nbd] [PATCH 3/1] doc: Propose Structured Replies extension

[Wouter Verhelst <w@uter.be>]

On Tue, Mar 29, 2016 at 12:07:59PM -0600, Eric Blake wrote:
> On 03/29/2016 12:03 PM, Wouter Verhelst wrote:
> > On Tue, Mar 29, 2016 at 11:45:45AM -0600, Eric Blake wrote:
> >> Supporting DF merely transfers the burden of collection between server
> >> and client.  I suspect that there are cases where the server does NOT
> >> want to support DF (because it would require the server to allocate
> >> memory to collect the data before sending a single structured read
> >> reply),
> > 
> > There are other ways to handle that; e.g., the server could have a
> > "request too large for non-fragmented read" error message. The spec
> > should give a minimum size that the server MUST support (which should be
> > reasonably large), and should state that a server MAY reply to any
> > request with DF set for a block larger than that minimum, with that
> > error.
> 
> How does 64k sound?

Dunno. It might make sense for this number to be based upon some
"standard" minimum request size in things like ATA or SCSI if such a
number exists there, but I don't know enough about either standard to
answer that question myself.

If such a number doesn't exist (or nobody who knows speaks up soon
enough), 64k is certainly good enough, I suppose.

-- 
< ron> I mean, the main *practical* problem with C++, is there's like a dozen
       people in the world who think they really understand all of its rules,
       and pretty much all of them are just lying to themselves too.
 -- #debian-devel, OFTC, 2016-02-12