Re: [Qemu-devel] [RFC PATCH RDMA support v1: 10/13] introduce new command migrate_check_for_zero

[Paolo Bonzini]

Il 11/04/2013 18:02, Michael R. Hines ha scritto:
> Alright, so here's a slightly different management decision
> which tries to accomplish all the requests,
> tell me if you like it:
> 
> 1. QEMU starts up
> 2. *if and only if* chunk registration is disabled
>     and *if and only* RDMA is enabled
>             then, is_dup_page() is skipped
>     Otherwise,
>             everything is same as before, no change in code path
>             and no zero page capability needs to be exposed to management
> 
> In this case there would be *no* capability for zero pages,
> but we would still be able to detect the motivation of the
> user indirectly through the chunk registration capability
> by implying that since the capability was disabled then the
> user is trying to optimize metrics for total migration time.
> 
> On the other hand, if the chunk registration capability is
> enabled, then there is no change in the code path we because
> zero page checking is mandatory to take of chunk registration
> in the first place.
> 
> How does that sound? No zero page capability, but allow for
> disabling only if chunk registration is disabled?

It makes sense, but I prefer to keep the code simple for this first
iteration.  Let's move zero page detection off the table for now.

Paolo