From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shirley Ma Subject: Re: Network performance with small packets - continued Date: Wed, 09 Mar 2011 07:45:43 -0800 Message-ID: <1299685543.25664.97.camel@localhost.localdomain> References: <201103071631.41964.tahm@linux.vnet.ibm.com> <20110309071558.GA25757@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Rusty Russell , Krishna Kumar2 , David Miller , kvm@vger.kernel.org, netdev@vger.kernel.org, steved@us.ibm.com, Tom Lendacky To: "Michael S. Tsirkin" Return-path: Received: from e3.ny.us.ibm.com ([32.97.182.143]:52764 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757010Ab1CIPpv (ORCPT ); Wed, 9 Mar 2011 10:45:51 -0500 In-Reply-To: <20110309071558.GA25757@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2011-03-09 at 09:15 +0200, Michael S. Tsirkin wrote: > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 82dba5a..ebe3337 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -514,11 +514,11 @@ static unsigned int free_old_xmit_skbs(struct > virtnet_info *vi) > struct sk_buff *skb; > unsigned int len, tot_sgs = 0; > > - while ((skb = virtqueue_get_buf(vi->svq, &len)) != NULL) { > + if ((skb = virtqueue_get_buf(vi->svq, &len)) != NULL) { > pr_debug("Sent skb %p\n", skb); > vi->dev->stats.tx_bytes += skb->len; > vi->dev->stats.tx_packets++; > - tot_sgs += skb_vnet_hdr(skb)->num_sg; > + tot_sgs = 2+MAX_SKB_FRAGS; > dev_kfree_skb_any(skb); > } > return tot_sgs; Return value should be different based on indirect or direct buffers here? > @@ -576,9 +576,6 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, > struct net_device *dev) > struct virtnet_info *vi = netdev_priv(dev); > int capacity; > > - /* Free up any pending old buffers before queueing new ones. > */ > - free_old_xmit_skbs(vi); > - > /* Try to transmit */ > capacity = xmit_skb(vi, skb); > > @@ -605,6 +602,10 @@ static netdev_tx_t start_xmit(struct sk_buff > *skb, struct net_device *dev) > skb_orphan(skb); > nf_reset(skb); > > + /* Free up any old buffers so we can queue new ones. */ > + if (capacity < 2+MAX_SKB_FRAGS) > + capacity += free_old_xmit_skbs(vi); > + > /* Apparently nice girls don't return TX_BUSY; stop the queue > * before it gets out of hand. Naturally, this wastes > entries. */ > if (capacity < 2+MAX_SKB_FRAGS) { I tried a similar patch before, it didn't help much on TCP stream performance. But I didn't try multiple stream TCP_RR. Shirley