Re: [Qemu-devel] [PATCH v2 11/12] mirror: support more than one in-flight AIO operation

[Paolo Bonzini]

Il 21/01/2013 13:35, Kevin Wolf ha scritto:
> I'm wondering if a whole bitmap is really appropriate when you have at
> most 16 parallel requests in flight. Other places in qemu (like
> copy-on-read or qcow2 cluster allocation) use lists of in-flight
> requests instead.
> 
> I'm not requesting a change here, just wondering what the reasons are
> and whether this, or the other places, or none of both should be changed
> long term.

The reason is simply that the code is reasoning in bitmaps a lot
(cow_bitmap and of course the dirty bitmap), so it was a natural pick
and the memory usage is not important.  It is simpler and more efficient
than a linear scan.

I have the required information already in the MirrorOp struct indeed,
but I didn't need those in a list.

Paolo