Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757331Ab0FUCoB (ORCPT ); Sun, 20 Jun 2010 22:44:01 -0400 Received: from ozlabs.org ([203.10.76.45]:59714 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755962Ab0FUCn4 (ORCPT ); Sun, 20 Jun 2010 22:43:56 -0400 From: Rusty Russell To: "Michael S. Tsirkin" Subject: Re: [PATCH for-2.6.35] virtio_net: fix oom handling on tx Date: Mon, 21 Jun 2010 12:13:49 +0930 User-Agent: KMail/1.13.2 (Linux/2.6.32-22-generic; KDE/4.4.2; i686; ; ) Cc: Stephen Hemminger , Sridhar Samudrala , virtualization@lists.linux-foundation.org, Jiri Pirko , Shirley Ma , netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20100610152041.GA3480@redhat.com> <20100610104653.1aed2ecc@nehalam> <20100610190343.GC4044@redhat.com> In-Reply-To: <20100610190343.GC4044@redhat.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201006211213.49600.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2963 Lines: 89 On Fri, 11 Jun 2010 04:33:43 am Michael S. Tsirkin wrote: > > > > @@ -572,12 +571,14 @@ again: > > > > > > > > /* This can happen with OOM and indirect buffers. */ > > > > if (unlikely(capacity < 0)) { > > > > - netif_stop_queue(dev); > > > > - dev_warn(&dev->dev, "Unexpected full queue\n"); > > > > - if (unlikely(!virtqueue_enable_cb(vi->svq))) { > > > > - virtqueue_disable_cb(vi->svq); > > > > - netif_start_queue(dev); > > > > - goto again; > > > > + if (net_ratelimit()) { > > > > + if (likely(capacity == -ENOMEM)) > > > > + dev_warn(&dev->dev, > > > > + "TX queue failure: out of memory\n"); > > > > + else > > > > + dev_warn(&dev->dev, > > > > + "Unexpected TX queue failure: %d\n", > > > > + capacity); ... > > Well, I only keep the existing behaviour around. Actually, it *does* change behavior, as the comment indicates. So let's fix the whole thing. AFAICT wth TX_BUSY we'll get called again RSN, and that's not really useful for OOM. This is what I have: Subject: virtio_net: fix oom handling on tx Date: Thu, 10 Jun 2010 18:20:41 +0300 From: "Michael S. Tsirkin" virtio net will never try to overflow the TX ring, so the only reason add_buf may fail is out of memory. Thus, we can not stop the device until some request completes - there's no guarantee anything at all is outstanding. Make the error message clearer as well: error here does not indicate queue full. Signed-off-by: Michael S. Tsirkin Signed-off-by: Rusty Russell (...and avoid TX_BUSY) Cc: stable@kernel.org --- drivers/net/virtio_net.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) 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 @@ -562,7 +562,6 @@ static netdev_tx_t start_xmit(struct sk_ struct virtnet_info *vi = netdev_priv(dev); int capacity; -again: /* Free up any pending old buffers before queueing new ones. */ free_old_xmit_skbs(vi); @@ -571,14 +570,17 @@ again: /* This can happen with OOM and indirect buffers. */ if (unlikely(capacity < 0)) { - netif_stop_queue(dev); - dev_warn(&dev->dev, "Unexpected full queue\n"); - if (unlikely(!virtqueue_enable_cb(vi->svq))) { - virtqueue_disable_cb(vi->svq); - netif_start_queue(dev); - goto again; + if (net_ratelimit()) { + if (likely(capacity == -ENOMEM)) + dev_warn(&dev->dev, + "TX queue failure: out of memory\n"); + else + dev_warn(&dev->dev, + "Unexpected TX queue failure: %d\n", + capacity); } - return NETDEV_TX_BUSY; + kfree_skb(skb); + return NETDEV_TX_OK; } virtqueue_kick(vi->svq); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/