Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Stefan Hajnoczi <stefanha@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1892 bytes --]

On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
> 
> Here is new parameter qiov_offset for io path, to avoid
> a lot of places with same pattern of creating local_qiov or hd_qiov
> variables.
> 
> These series also includes my
> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
> with some changes [described in 01 and 03 emails]
> 
> Vladimir Sementsov-Ogievskiy (12):
>   util/iov: introduce qemu_iovec_init_extended
>   util/iov: improve qemu_iovec_is_zero
>   block/io: refactor padding
>   block: define .*_part io handlers in BlockDriver
>   block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>   block/io: bdrv_co_do_copy_on_readv: lazy allocation
>   block/io: bdrv_aligned_preadv: use and support qiov_offset
>   block/io: bdrv_aligned_pwritev: use and support qiov_offset
>   block/io: introduce bdrv_co_p{read,write}v_part
>   block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>   block/qcow2: implement .bdrv_co_preadv_part
>   block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
> 
>  block/qcow2.h             |   1 +
>  include/block/block_int.h |  21 ++
>  include/qemu/iov.h        |  10 +-
>  block/backup.c            |   2 +-
>  block/io.c                | 532 ++++++++++++++++++++++----------------
>  block/qcow2-cluster.c     |  14 +-
>  block/qcow2.c             | 131 +++++-----
>  qemu-img.c                |   4 +-
>  util/iov.c                | 153 +++++++++--
>  9 files changed, 559 insertions(+), 309 deletions(-)
> 
> -- 
> 2.18.0
> 
> 

I don't see a significant advantage after taking into account more
complex code (e.g. additional block driver interfaces) and the risk of
introducing new bugs.  A measurable performance improvement would make
this refactoring more attractive.  Still:

Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]