Re: [Qemu-devel] [PATCH 02/10] virtio: move allocation to virtqueue_pop/vring_pop

[Cornelia Huck]

On Sun, 31 Jan 2016 11:28:58 +0100
Paolo Bonzini <address@hidden> wrote:

> The return code of virtqueue_pop/vring_pop is unused except to check for
> errors or 0.  We can thus easily move allocation inside the functions
> and just return a pointer to the VirtQueueElement.
> 
> The advantage is that we will be able to allocate only the space that
> is needed for the actual size of the s/g list instead of the full
> VIRTQUEUE_MAX_SIZE items.  Currently VirtQueueElement takes about 48K
> of memory, and this kind of allocation puts a lot of stress on malloc.
> By cutting the size by two or three orders of magnitude, malloc can
> use much more efficient algorithms.
> 
> The patch is pretty large, but changes to each device are testable
> more or less independently.  Splitting it would mostly add churn.
> 
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>         v1->v2: add assertions on sz [Conny]
> 
>  hw/9pfs/9p.c                        |  2 +-
>  hw/9pfs/virtio-9p-device.c          | 17 ++++----
>  hw/9pfs/virtio-9p.h                 |  2 +-
>  hw/block/dataplane/virtio-blk.c     | 11 +++--
>  hw/block/virtio-blk.c               | 15 +++----
>  hw/char/virtio-serial-bus.c         | 80 
> +++++++++++++++++++++++--------------
>  hw/display/virtio-gpu.c             | 25 +++++++-----
>  hw/input/virtio-input.c             | 24 +++++++----
>  hw/net/virtio-net.c                 | 69 ++++++++++++++++++++------------
>  hw/scsi/virtio-scsi-dataplane.c     | 15 +++----
>  hw/scsi/virtio-scsi.c               | 18 ++++-----
>  hw/virtio/dataplane/vring.c         | 18 +++++----
>  hw/virtio/virtio-balloon.c          | 22 ++++++----
>  hw/virtio/virtio-rng.c              | 10 +++--
>  hw/virtio/virtio.c                  | 12 ++++--
>  include/hw/virtio/dataplane/vring.h |  2 +-
>  include/hw/virtio/virtio-balloon.h  |  2 +-
>  include/hw/virtio/virtio-blk.h      |  3 +-
>  include/hw/virtio/virtio-net.h      |  2 +-
>  include/hw/virtio/virtio-scsi.h     |  2 +-
>  include/hw/virtio/virtio-serial.h   |  2 +-
>  include/hw/virtio/virtio.h          |  2 +-
>  22 files changed, 212 insertions(+), 143 deletions(-)

Reviewed-by: Cornelia Huck <address@hidden>