Re: [Qemu-devel] [RFC] block-queue: Delay and batch metadata writes

[Avi Kivity]

 On 09/20/2010 05:08 PM, Kevin Wolf wrote:
> >
> >  Let's expand it a bit more:
> >
> >  1. Update refcount table
> >  2. bdrv_flush
> >  3. Update L2 entry
> >  4. Write data to disk
> >  5. Report write complete
> >
> >  I'm struggling to understand how a thread helps out.
>
> This sequence becomes:
>
> 1. Update refcount table
> 2. Write data to disk
> 3. Report write complete
>
> And only later:
>
> 4. Update L2 entry
> 5. bdrv_flush (possibly merged with other flushes)

The L2 update needs to happen after we're sure the refcount update is 
stable, so need a bdrv_flush between them.

Still, the basic idea looks sound.  You can do many refcount updates, 
flush, many L2 updates, flush.

--
error compiling committee.c: too many arguments to function