Re: [PATCH v3] virtio: increase virtqueue size for virtio-scsi and virtio-blk

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Fri, Feb 14, 2020 at 10:46:48AM +0300, Denis Plotnikov wrote:
> The goal is to reduce the amount of requests issued by a guest on
> 1M reads/writes. This rises the performance up to 4% on that kind of
> disk access pattern.
> 
> The maximum chunk size to be used for the guest disk accessing is
> limited with seg_max parameter, which represents the max amount of
> pices in the scatter-geather list in one guest disk request.
> 
> Since seg_max is virqueue_size dependent, increasing the virtqueue
> size increases seg_max, which, in turn, increases the maximum size
> of data to be read/write from a guest disk.
> 
> More details in the original problem statment:
> https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg03721.html
> 
> Suggested-by: Denis V. Lunev <den@openvz.org>
> Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
> 
> ---
> 
> v3:
>   * typos fixed
> 
> v2:
>   * seg_max default value changing removed
> ---
>  hw/block/virtio-blk.c | 2 +-
>  hw/core/machine.c     | 2 ++
>  hw/scsi/virtio-scsi.c | 2 +-
>  3 files changed, 4 insertions(+), 2 deletions(-)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

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