Re: [Qemu-block] [PATCH] vpc: unlock Coroutine lock to make IO submit Concurrently

[Paolo Bonzini]

On 15/03/19 15:04, Zhengui li wrote:
> Concurrent IO becomes serial IO because of the qemu Coroutine lock,
> which reduce IO performance severely.
> 
> So unlock Coroutine lock before bdrv_co_pwritev and
> bdrv_co_preadv to fix it.
> 
> Signed-off-by: Zhengui li <address@hidden>
> ---
>  block/vpc.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/block/vpc.c b/block/vpc.c
> index 52ab717..1133855 100644
> --- a/block/vpc.c
> +++ b/block/vpc.c
> @@ -639,8 +639,10 @@ vpc_co_preadv(BlockDriverState *bs, uint64_t offset, 
> uint64_t bytes,
>              qemu_iovec_reset(&local_qiov);
>              qemu_iovec_concat(&local_qiov, qiov, bytes_done, n_bytes);
>  
> +            qemu_co_mutex_unlock(&s->lock);
>              ret = bdrv_co_preadv(bs->file, image_offset, n_bytes,
>                                   &local_qiov, 0);
> +            qemu_co_mutex_lock(&s->lock);
>              if (ret < 0) {
>                  goto fail;
>              }
> @@ -697,8 +699,10 @@ vpc_co_pwritev(BlockDriverState *bs, uint64_t offset, 
> uint64_t bytes,
>          qemu_iovec_reset(&local_qiov);
>          qemu_iovec_concat(&local_qiov, qiov, bytes_done, n_bytes);
>  
> +        qemu_co_mutex_unlock(&s->lock);
>          ret = bdrv_co_pwritev(bs->file, image_offset, n_bytes,
>                                &local_qiov, 0);
> +        qemu_co_mutex_lock(&s->lock);
>          if (ret < 0) {
>              goto fail;
>          }
> 

This should be okay, because vpc.c is somewhat simple-minded and it
doesn't recycle unused blocks in the middle of the file.

Reviewed-by: Paolo Bonzini <address@hidden>

Paolo