Re: [Qemu-devel] [RFC V1 12/14] qcow2: Add qcow2_dedup_update_metrics to compute dedup RAM usage.

[Eric Blake]

On 01/16/2013 09:25 AM, Benoît Canet wrote:
> ---
>  block/qcow2-dedup.c |   13 +++++++++++++
>  block/qcow2.h       |    1 +
>  2 files changed, 14 insertions(+)
> 
> diff --git a/block/qcow2-dedup.c b/block/qcow2-dedup.c
> index db23b71..4305746 100644
> --- a/block/qcow2-dedup.c
> +++ b/block/qcow2-dedup.c
> @@ -1311,3 +1311,16 @@ void qcow2_dedup_close(BlockDriverState *bs)
>  {
>      qcow2_dedup_free(bs);
>  }
> +
> +#define GTREE_NODE_SIZE sizeof(int) * 5

Improperly parenthesized.  Also, this feels like a magic number, is
there an actual sizeof(struct) you could use instead of hand-computing
how much is used per node?

> +
> +void qcow2_dedup_update_metrics(BlockDriverState *bs)
> +{
> +    BDRVQcowState *s = bs->opaque;
> +
> +    uint64_t nb_hashs = s->dedup_metrics.ram_hash_creations -
> +                        s->dedup_metrics.ram_hash_deletions;
> +
> +    s->dedup_metrics.ram_usage = nb_hashs * GTREE_NODE_SIZE * 2;

But you got lucky that order of operations didn't care about the missing
() here.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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