On 22/08/2015 00:53, Paolo Bonzini wrote:
> VIRTIO_BLK_F_CONFIG_WCE is important in order to achieve good performance
> (up to 2x, though more realistically +30-40%) in latency-bound workloads.
> However, it was removed by mistake together with VIRTIO_BLK_F_FLUSH.
>
> It will be restored in the next revision of the virtio 1.0 standard, so
> do the same in Linux.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> drivers/block/virtio_blk.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index d4d05f064d39..ea2c17c66dfb 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -478,8 +478,7 @@ static int virtblk_get_cache_mode(struct virtio_device *vdev)
> struct virtio_blk_config, wce,
> &writeback);
> if (err)
> - writeback = virtio_has_feature(vdev, VIRTIO_BLK_F_WCE) ||
> - virtio_has_feature(vdev, VIRTIO_F_VERSION_1);
> + writeback = virtio_has_feature(vdev, VIRTIO_BLK_F_WCE);
>
> return writeback;
> }
> @@ -840,7 +839,7 @@ static unsigned int features_legacy[] = {
> static unsigned int features[] = {
> VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_GEOMETRY,
> VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
> - VIRTIO_BLK_F_TOPOLOGY,
> + VIRTIO_BLK_F_WCE, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
> VIRTIO_BLK_F_MQ,
> };
>
>
Ping?
Paolo
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