Re: [Qemu-devel] [PATCH] net: reduce the unnecessary memory allocation of multiqueue

[Anthony Liguori]

Jason Wang <address@hidden> writes:

> Edivaldo reports a problem that the array of NetClientState in NICState is too
> large - MAX_QUEUE_NUM(1024) which will wastes memory even if multiqueue is not
> used.
>
> Instead of static arrays, solving this issue by allocating the queues on 
> demand
> for both the NetClientState array in NICState and VirtIONetQueue array in
> VirtIONet.
>
> Tested by myself, with single virtio-net-pci device. The memory allocation is
> almost the same as when multiqueue is not merged.
>
> Cc: Edivaldo de Araujo Pereira <address@hidden>
> Cc: address@hidden
> Signed-off-by: Jason Wang <address@hidden>
> ---
>  hw/virtio-net.c   |    6 ++++--
>  include/net/net.h |    2 +-
>  net/net.c         |   19 +++++++++----------
>  3 files changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index 573c669..70ab641 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -44,7 +44,7 @@ typedef struct VirtIONet
>      VirtIODevice vdev;
>      uint8_t mac[ETH_ALEN];
>      uint16_t status;
> -    VirtIONetQueue vqs[MAX_QUEUE_NUM];
> +    VirtIONetQueue *vqs;
>      VirtQueue *ctrl_vq;
>      NICState *nic;
>      uint32_t tx_timeout;
> @@ -1326,8 +1326,9 @@ VirtIODevice *virtio_net_init(DeviceState *dev, NICConf 
> *conf,
>      n->vdev.set_status = virtio_net_set_status;
>      n->vdev.guest_notifier_mask = virtio_net_guest_notifier_mask;
>      n->vdev.guest_notifier_pending = virtio_net_guest_notifier_pending;
> +    n->max_queues = MAX(conf->queues, 1);

I think you mean MIN here.

> +    n->vqs = g_malloc0(sizeof(VirtIONetQueue) * n->max_queues);
>      n->vqs[0].rx_vq = virtio_add_queue(&n->vdev, 256, virtio_net_handle_rx);
> -    n->max_queues = conf->queues;
>      n->curr_queues = 1;
>      n->vqs[0].n = n;
>      n->tx_timeout = net->txtimer;
> @@ -1397,6 +1398,7 @@ void virtio_net_exit(VirtIODevice *vdev)
>  
>      g_free(n->mac_table.macs);
>      g_free(n->vlans);
> +    g_free(n->vqs);
>  
>      for (i = 0; i < n->max_queues; i++) {
>          VirtIONetQueue *q = &n->vqs[i];
> diff --git a/include/net/net.h b/include/net/net.h
> index 43a045e..cb049a1 100644
> --- a/include/net/net.h
> +++ b/include/net/net.h
> @@ -72,7 +72,7 @@ struct NetClientState {
>  };
>  
>  typedef struct NICState {
> -    NetClientState ncs[MAX_QUEUE_NUM];
> +    NetClientState *ncs;
>      NICConf *conf;
>      void *opaque;
>      bool peer_deleted;
> diff --git a/net/net.c b/net/net.c
> index be03a8d..6262ed0 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -235,23 +235,20 @@ NICState *qemu_new_nic(NetClientInfo *info,
>                         const char *name,
>                         void *opaque)
>  {
> -    NetClientState *nc;
>      NetClientState **peers = conf->peers.ncs;
>      NICState *nic;
> -    int i;
> +    int i, queues = MAX(1, conf->queues);

And here.  This patch is what had created problems for me.

Regards,

Anthony Liguori

>  
>      assert(info->type == NET_CLIENT_OPTIONS_KIND_NIC);
>      assert(info->size >= sizeof(NICState));
>  
> -    nc = qemu_new_net_client(info, peers[0], model, name);
> -    nc->queue_index = 0;
> -
> -    nic = qemu_get_nic(nc);
> +    nic = g_malloc0(info->size + sizeof(NetClientState) * queues);
> +    nic->ncs = (void *)nic + info->size;
>      nic->conf = conf;
>      nic->opaque = opaque;
>  
> -    for (i = 1; i < conf->queues; i++) {
> -        qemu_net_client_setup(&nic->ncs[i], info, peers[i], model, nc->name,
> +    for (i = 0; i < queues; i++) {
> +        qemu_net_client_setup(&nic->ncs[i], info, peers[i], model, name,
>                                NULL);
>          nic->ncs[i].queue_index = i;
>      }
> @@ -261,7 +258,7 @@ NICState *qemu_new_nic(NetClientInfo *info,
>  
>  NetClientState *qemu_get_subqueue(NICState *nic, int queue_index)
>  {
> -    return &nic->ncs[queue_index];
> +    return nic->ncs + queue_index;
>  }
>  
>  NetClientState *qemu_get_queue(NICState *nic)
> @@ -273,7 +270,7 @@ NICState *qemu_get_nic(NetClientState *nc)
>  {
>      NetClientState *nc0 = nc - nc->queue_index;
>  
> -    return DO_UPCAST(NICState, ncs[0], nc0);
> +    return (NICState *)((void *)nc0 - nc->info->size);
>  }
>  
>  void *qemu_get_nic_opaque(NetClientState *nc)
> @@ -368,6 +365,8 @@ void qemu_del_nic(NICState *nic)
>          qemu_cleanup_net_client(nc);
>          qemu_free_net_client(nc);
>      }
> +
> +    g_free(nic);
>  }
>  
>  void qemu_foreach_nic(qemu_nic_foreach func, void *opaque)
> -- 
> 1.7.1