Re: request->ioprio

[Fernando Luis Vázquez Cao]

On Thu, 2008-08-14 at 12:16 +1000, Rusty Russell wrote:
> On Wednesday 13 August 2008 17:06:03 Fernando Luis VÃzquez Cao wrote:
> > Besides, I guess that accessing the io context information (such as
> > ioprio) of a request through elevator-specific private structures is not
> > something we want virtio_blk (or future users) to do.
> 
> The only semantic I assumed was "higher is better".  The server (ie. host) can 
> really only use the information to schedule between I/Os for that particular 
> guest anyway.
> 
> But it sounds like I should be passing "0" in there unconditionally until the 
> kernel semantics are sorted out and I can do something more intelligent?  I 
> haven't checked, but I assume that's actually what's happening at the moment 
> (the field is zero)?
Yes, with the current implementation the field is always zero, but
things might change. Instead of passing 0 unconditionally I think we
could use a function that extracts/calculates the ioprio of requests.
The patch I sent you yesterday is the first step in that direction. Is
this a valid approach for you?

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