Re: [Qemu-devel] [RFC v5] RBD: Add support readv,writev for rbd

[Tiger Hu]

Tianqing,

Do we have any performance data for this patch? Thanks.

Tiger
> 在 2017年2月16日，下午5:address@hidden 写道：
> 
> From: tianqing <address@hidden>
> 
> Rbd can do readv and writev directly, so wo do not need to transform
> iov to buf or vice versa any more.
> 
> Signed-off-by: tianqing <address@hidden>
> ---
> block/rbd.c | 49 ++++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 42 insertions(+), 7 deletions(-)
> 
> diff --git a/block/rbd.c b/block/rbd.c
> index a57b3e3..75ae1d6 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -47,7 +47,7 @@
>  */
> 
> /* rbd_aio_discard added in 0.1.2 */
> -#if LIBRBD_VERSION_CODE >= LIBRBD_VERSION(0, 1, 2)
> +#if LIBRBD_VERSION_CODE >= LIBRBD_VERSION(12, 0, 0)
> #define LIBRBD_SUPPORTS_DISCARD
> #else
> #undef LIBRBD_SUPPORTS_DISCARD
> @@ -73,7 +73,12 @@ typedef struct RBDAIOCB {
>     BlockAIOCB common;
>     int64_t ret;
>     QEMUIOVector *qiov;
> +/* Note:
> + * The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h.
> + */
> +#ifndef LIBRBD_SUPPORTS_IOVEC
>     char *bounce;
> +#endif
>     RBDAIOCmd cmd;
>     int error;
>     struct BDRVRBDState *s;
> @@ -83,7 +88,9 @@ typedef struct RADOSCB {
>     RBDAIOCB *acb;
>     struct BDRVRBDState *s;
>     int64_t size;
> +#ifndef LIBRBD_SUPPORTS_IOVEC
>     char *buf;
> +#endif
>     int64_t ret;
> } RADOSCB;
> 
> @@ -426,11 +433,21 @@ static void qemu_rbd_complete_aio(RADOSCB *rcb)
>         }
>     } else {
>         if (r < 0) {
> +#ifndef LIBRBD_SUPPORTS_IOVEC
>             memset(rcb->buf, 0, rcb->size);
> +#else
> +            iov_memset(acb->qiov->iov, acb->qiov->niov, 0, 0, 
> acb->qiov->size);
> +#endif
>             acb->ret = r;
>             acb->error = 1;
>         } else if (r < rcb->size) {
> +#ifndef LIBRBD_SUPPORTS_IOVEC
>             memset(rcb->buf + r, 0, rcb->size - r);
> +#else
> +            iov_memset(acb->qiov->iov, acb->qiov->niov,
> +                       r, 0, acb->qiov->size - r);
> +#endif
> +
>             if (!acb->error) {
>                 acb->ret = rcb->size;
>             }
> @@ -441,10 +458,12 @@ static void qemu_rbd_complete_aio(RADOSCB *rcb)
> 
>     g_free(rcb);
> 
> +#ifndef LIBRBD_SUPPORTS_IOVEC
>     if (acb->cmd == RBD_AIO_READ) {
>         qemu_iovec_from_buf(acb->qiov, 0, acb->bounce, acb->qiov->size);
>     }
>     qemu_vfree(acb->bounce);
> +#endif
>     acb->common.cb(acb->common.opaque, (acb->ret > 0 ? 0 : acb->ret));
> 
>     qemu_aio_unref(acb);
> @@ -655,8 +674,10 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
>     RBDAIOCB *acb;
>     RADOSCB *rcb = NULL;
>     rbd_completion_t c;
> -    char *buf;
>     int r;
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> +    char *buf = NULL;
> +#endif
> 
>     BDRVRBDState *s = bs->opaque;
> 
> @@ -664,6 +685,8 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
>     acb->cmd = cmd;
>     acb->qiov = qiov;
>     assert(!qiov || qiov->size == size);
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> +
>     if (cmd == RBD_AIO_DISCARD || cmd == RBD_AIO_FLUSH) {
>         acb->bounce = NULL;
>     } else {
> @@ -672,19 +695,21 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
>             goto failed;
>         }
>     }
> -    acb->ret = 0;
> -    acb->error = 0;
> -    acb->s = s;
> -
>     if (cmd == RBD_AIO_WRITE) {
>         qemu_iovec_to_buf(acb->qiov, 0, acb->bounce, qiov->size);
>     }
> -
>     buf = acb->bounce;
> +#endif
> +    acb->ret = 0;
> +    acb->error = 0;
> +    acb->s = s;
> 
>     rcb = g_new(RADOSCB, 1);
> +
>     rcb->acb = acb;
> +#ifndef LIBRBD_SUPPORTS_IOVEC
>     rcb->buf = buf;
> +#endif
>     rcb->s = acb->s;
>     rcb->size = size;
>     r = rbd_aio_create_completion(rcb, (rbd_callback_t) rbd_finish_aiocb, &c);
> @@ -694,10 +719,18 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
> 
>     switch (cmd) {
>     case RBD_AIO_WRITE:
> +#ifndef LIBRBD_SUPPORTS_IOVEC
>         r = rbd_aio_write(s->image, off, size, buf, c);
> +#else
> +        r = rbd_aio_writev(s->image, qiov->iov, qiov->niov, off, c);
> +#endif
>         break;
>     case RBD_AIO_READ:
> +#ifndef LIBRBD_SUPPORTS_IOVEC
>         r = rbd_aio_read(s->image, off, size, buf, c);
> +#else
> +        r = rbd_aio_readv(s->image, qiov->iov, qiov->niov, off, c);
> +#endif
>         break;
>     case RBD_AIO_DISCARD:
>         r = rbd_aio_discard_wrapper(s->image, off, size, c);
> @@ -719,7 +752,9 @@ failed_completion:
>     rbd_aio_release(c);
> failed:
>     g_free(rcb);
> +#ifndef LIBRBD_SUPPORTS_IOVEC
>     qemu_vfree(acb->bounce);
> +#endif
>     qemu_aio_unref(acb);
>     return NULL;
> }
> -- 
> 2.10.2
> 
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