On Wed, 12 Aug 2009 12:49:51 pm Rusty Russell wrote: > On Tue, 11 Aug 2009 04:22:53 pm Avi Kivity wrote: > > On 08/11/2009 09:32 AM, Pierre Ossman wrote: > > > I doesn't get out of it though, or at least the virtio net driver > > > wedges itself. > > There's a fixme to retry when this happens, but this is the first report > I've received. I'll check it out.
Subject: virtio: net refill on out-of-memory If we run out of memory, use keventd to fill the buffer. There's a report of this happening: "Page allocation failures in guest", Message-ID: <[email protected]> Signed-off-by: Rusty Russell <[email protected]> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -71,6 +71,9 @@ struct virtnet_info struct sk_buff_head recv; struct sk_buff_head send; + /* Work struct for refilling if we run low on memory. */ + struct work_struct refill; + /* Chain pages by the private ptr. */ struct page *pages; }; @@ -274,19 +277,22 @@ drop: dev_kfree_skb(skb); } -static void try_fill_recv_maxbufs(struct virtnet_info *vi) +static bool try_fill_recv_maxbufs(struct virtnet_info *vi, gfp_t gfp) { struct sk_buff *skb; struct scatterlist sg[2+MAX_SKB_FRAGS]; int num, err, i; + bool oom = false; sg_init_table(sg, 2+MAX_SKB_FRAGS); for (;;) { struct virtio_net_hdr *hdr; skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN + NET_IP_ALIGN); - if (unlikely(!skb)) + if (unlikely(!skb)) { + oom = true; break; + } skb_reserve(skb, NET_IP_ALIGN); skb_put(skb, MAX_PACKET_LEN); @@ -297,7 +303,7 @@ static void try_fill_recv_maxbufs(struct if (vi->big_packets) { for (i = 0; i < MAX_SKB_FRAGS; i++) { skb_frag_t *f = &skb_shinfo(skb)->frags[i]; - f->page = get_a_page(vi, GFP_ATOMIC); + f->page = get_a_page(vi, gfp); if (!f->page) break; @@ -326,31 +332,35 @@ static void try_fill_recv_maxbufs(struct if (unlikely(vi->num > vi->max)) vi->max = vi->num; vi->rvq->vq_ops->kick(vi->rvq); + return !oom; } -static void try_fill_recv(struct virtnet_info *vi) +/* Returns false if we couldn't fill entirely (OOM). */ +static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp) { struct sk_buff *skb; struct scatterlist sg[1]; int err; + bool oom = false; - if (!vi->mergeable_rx_bufs) { - try_fill_recv_maxbufs(vi); - return; - } + if (!vi->mergeable_rx_bufs) + return try_fill_recv_maxbufs(vi, gfp); for (;;) { skb_frag_t *f; skb = netdev_alloc_skb(vi->dev, GOOD_COPY_LEN + NET_IP_ALIGN); - if (unlikely(!skb)) + if (unlikely(!skb)) { + oom = true; break; + } skb_reserve(skb, NET_IP_ALIGN); f = &skb_shinfo(skb)->frags[0]; - f->page = get_a_page(vi, GFP_ATOMIC); + f->page = get_a_page(vi, gfp); if (!f->page) { + oom = true; kfree_skb(skb); break; } @@ -374,6 +384,7 @@ static void try_fill_recv(struct virtnet if (unlikely(vi->num > vi->max)) vi->max = vi->num; vi->rvq->vq_ops->kick(vi->rvq); + return !oom; } static void skb_recv_done(struct virtqueue *rvq) @@ -386,6 +397,26 @@ static void skb_recv_done(struct virtque } } +static void refill_work(struct work_struct *work) +{ + struct virtnet_info *vi; + bool still_empty; + + vi = container_of(work, struct virtnet_info, refill); + napi_disable(&vi->napi); + try_fill_recv(vi, GFP_KERNEL); + still_empty = (vi->num == 0); + napi_enable(&vi->napi); + + /* In theory, this can happen: if we don't get any buffers in + * we will *never* try to fill again. Sleeping in keventd if + * bad, but that is worse. */ + if (still_empty) { + msleep(100); + schedule_work(&vi->refill); + } +} + static int virtnet_poll(struct napi_struct *napi, int budget) { struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi); @@ -401,10 +432,10 @@ again: received++; } - /* FIXME: If we oom and completely run out of inbufs, we need - * to start a timer trying to fill more. */ - if (vi->num < vi->max / 2) - try_fill_recv(vi); + if (vi->num < vi->max / 2) { + if (!try_fill_recv(vi, GFP_ATOMIC)) + schedule_work(&vi->refill); + } /* Out of packets? */ if (received < budget) { @@ -894,6 +925,7 @@ static int virtnet_probe(struct virtio_d vi->vdev = vdev; vdev->priv = vi; vi->pages = NULL; + INIT_WORK(&vi->refill, refill_work); /* If they give us a callback when all buffers are done, we don't need * the timer. */ @@ -942,7 +974,7 @@ static int virtnet_probe(struct virtio_d } /* Last of all, set up some receive buffers. */ - try_fill_recv(vi); + try_fill_recv(vi, GFP_KERNEL); /* If we didn't even get one input buffer, we're useless. */ if (vi->num == 0) { @@ -959,6 +991,7 @@ static int virtnet_probe(struct virtio_d unregister: unregister_netdev(dev); + cancel_work_sync(&vi->refill); free_vqs: vdev->config->del_vqs(vdev); free: @@ -987,6 +1020,7 @@ static void virtnet_remove(struct virtio BUG_ON(vi->num != 0); unregister_netdev(vi->dev); + cancel_work_sync(&vi->refill); vdev->config->del_vqs(vi->vdev); -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
