Re: [Qemu-devel] a suggestion to extend the query block stats commands for multi-disk case

[Dou Liyang]

Hi Paolo,Stefan,

At 12/05/2016 07:57 PM, Paolo Bonzini wrote:
> On 05/12/2016 12:53, Stefan Hajnoczi wrote:
> > Adding the BlockBackend *query_blk parameter is a reasonable short-term
> > workaround.  I wonder if the polling stats APIs need to be rethought in
> > the longer term.
> >
> > Regarding the low-level details of block statistics inside QEMU, we can
> > probably collect statistics without requiring the AioContext lock.  This
> > means guest I/O processing does not need to be interrupted.  There
> > should be some RCU-style scheme that can be used to extract the stats.
>
> The question is also what level of consistency you want.  Perhaps as
> long as you can access it atomically (so no tearing of values) you don't
> need a lock at all, blk_ref/unref is enough.

Yes, that is what I want to express. When I use the command frequently,
I may want to sacrifice consistency, in exchange for performance.


Thanks,

  Liyang.