Re: [Qemu-devel] qcow2 performance plan

[Avi Kivity]

 On 09/14/2010 06:16 PM, Anthony Liguori wrote:
> Right, it should only freeze if the L2 table needs to be allocated, 
> not if it only needs to be updated.  IOW,
>
> diff --git a/block/qed.c b/block/qed.c
> index 4c4e7a2..0357c03 100644
> --- a/block/qed.c
> +++ b/block/qed.c
> @@ -948,7 +948,7 @@ static void qed_aio_write_data(void *opaque, int ret,
>      }
>
>      /* Freeze this request if another allocating write is in progress */
> -    if (need_alloc) {
> +    if (ret == QED_CLUSTER_L1) {
>          if (acb != QSIMPLEQ_FIRST(&s->allocating_write_reqs)) {
>              QSIMPLEQ_INSERT_TAIL(&s->allocating_write_reqs, acb, next);
>          }
>
> It's being a bit more conservative than it needs to be.

Yes, I hit this too.  So without this patch, it does serialize all 
allocating writes?

If multiple requests need to update pointers in L2, will those updates 
generate one write per request, or just two writes (one write from the 
first request, another from all those that serialized after it)?

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