Re: [Qemu-devel] [PATCH v3 13/38] block: Remove wr_highest_sector from BlockAcctStats

[Eric Blake <eblake@redhat.com>]

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On 06/03/2015 01:43 PM, Max Reitz wrote:
> BlockAcctStats contains statistics about the data transferred from and
> to the device; wr_highest_sector does not fit in with the rest.
> 
> Furthermore, those statistics are supposed to be specific for a certain
> device and not necessarily for a BDS (see the comment above
> bdrv_get_stats()); on the other hand, wr_highest_sector may be a rather
> important information to know for each BDS. When BlockAcctStats is
> finally removed from the BDS, we will want to keep wr_highest_sector in
> the BDS.

See also Berto's thread on I/O accounting overhaul:
https://lists.gnu.org/archive/html/qemu-devel/2015-06/msg00994.html

I think eventually we want stats at both BDS and BB levels.  But for
now, you are must moving things around to where they make sense, so I
can live with it as incremental improvement.

> 
> Finally, wr_highest_sector is renamed to wr_highest_offset and given the
> appropriate meaning. Externally, it is represented as an offset so there
> is no point in doing something different internally. Its definition is
> changed to match that in qapi/block-core.json which is "the offset after
> the greatest byte written to". Doing so should not cause any harm since
> if external programs tried to calculate the volume usage by
> (wr_highest_offset + 512) / volume_size, after this patch they will just
> assume the volume to be full slightly earlier than before.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/accounting.c         | 8 --------
>  block/io.c                 | 4 +++-
>  block/qapi.c               | 4 ++--
>  include/block/accounting.h | 3 ---
>  include/block/block_int.h  | 3 +++
>  qmp-commands.hx            | 4 ++--
>  6 files changed, 10 insertions(+), 16 deletions(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

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


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