Re: [Qemu-devel] [PATCH v4 2/6] add basic backup support to block driver

[Dietmar Maurer]

> > Adding and IO queue and implement a scheduler is likely not what we want to
> do.
> 
> The starting point for something smarter than just no policy or rate-limiting 
> is
> BlockDriverState->tracked_requests.  block.c keeps track of active requests
> using this list.
> 
> The simplest policy using bs->tracked_requests is to only submit block job I/O
> requests when the list is empty.
> 
> Want to try this approach?  (The drawback is that the guest can starve the 
> block
> job by submitting I/O all the time.)

Already tried that, but the 1000ns delay behaves better (again, just a feeling, 
because
I found no way to measure that behaviour).