On Wed, 28 Apr 2010 12:47:49 -0500 Anthony Liguori <anth...@codemonkey.ws> wrote:
> On 04/28/2010 12:04 PM, Luiz Capitulino wrote: > > On Wed, 28 Apr 2010 11:01:12 -0500 > > Anthony Liguori<anth...@codemonkey.ws> wrote: > > > > > >> On 04/28/2010 10:56 AM, Kevin Wolf wrote: > >> > >>> This adds the wr_highest_sector blockstat which implements what is > >>> generally > >>> known as the high watermark. It is the highest offset of a sector written > >>> to > >>> the respective BlockDriverState since it has been opened. > >>> > >>> The query-blockstat QMP command is extended to add this value to the > >>> result, > >>> and also to add the statistics of the underlying protocol in a new > >>> "parent" > >>> field. Note that to get the "high watermark" of a qcow2 image, you need > >>> to look > >>> into the wr_highest_sector field of the parent (which can be a file, a > >>> host_device, ...). The wr_highest_sector of the qcow2 BlockDriverState > >>> itself > >>> is the highest offset on the _virtual_ disk that the guest has written to. > >>> > >>> Signed-off-by: Kevin Wolf<kw...@redhat.com> > >>> > >>> > >> I see, you did print out stats for each layer. > >> > >> I don't think we should take 2/2. I don't mind QMP having more features > >> than the user monitor. > >> > > I don't either, but Kevin has said to me that this information is also > > good > > for the user Monitor. > > > > The real question here is whether or not we're going to stop supporting > > stability for the user Monitor and if so, when we'll break it. > > > > An arguable reasonable policy would be to try to maintain stability for > > existing commands. In this specific case, 'info blockstats' is used by > > libvirt afaik. So breaking it would mean that older libvirt versions won't > > be able to talk to newer qemu (taking libvirt just as real known example). > > > > I think we should try our best to maintain compatibility. In this case, > this change would break any non-QMP version of libvirt so it would be > pretty painful for users. That's why I'm inclined to not take. > > It would be reasonable to add a new info command for the user monitor if > the functionality is desirable. Seems a good solution to me too.