Re: [PATCH] macvtap: Fix macvtap_get_queue to use rxhash first
From: jasowang <jasowang@redhat.com>
Date: 2011-11-24 09:36:40
Also in:
virtualization
On 11/24/2011 04:17 PM, Krishna Kumar wrote:
quoted hunk ↗ jump to hunk
It was reported that the macvtap device selects a different vhost (when used with multiqueue feature) for incoming packets of a single connection. Use packet hash first. Patch tested on MQ virtio_net. Signed-off-by: Krishna Kumar<redacted> --- drivers/net/macvtap.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff -ruNp org/drivers/net/macvtap.c new/drivers/net/macvtap.c--- org/drivers/net/macvtap.c 2011-10-22 08:38:01.000000000 +0530 +++ new/drivers/net/macvtap.c 2011-11-16 18:34:51.000000000 +0530@@ -175,6 +175,14 @@ static struct macvtap_queue *macvtap_get if (!numvtaps) goto out; + /* Check if we can use flow to select a queue */ + rxq = skb_get_rxhash(skb); + if (rxq) { + tap = rcu_dereference(vlan->taps[rxq % numvtaps]); + if (tap) + goto out; + } + if (likely(skb_rx_queue_recorded(skb))) { rxq = skb_get_rx_queue(skb);
Looks reasonable and we can improve this further by implementing smarter queue selection with the co-operation of guest. I think one initiate of this is to let the packets of a flow to be handled by the same guest cpu/vhost thread. This can be done by using accelerate rfs in virtio-net driver and 'tell' the macvtap/tap which queue should a packet go. I've started working on prototype of this, it should solves the issue of packet steering in guest. One more thought on this is, If a nic (such as ixgbe) with flow director or similar technology is used, it can make sure the packet belongs to a flow to be handled by host cpu. If we can make use of this feature, more cache locality would be gained.
quoted hunk ↗ jump to hunk
@@ -186,14 +194,6 @@ static struct macvtap_queue *macvtap_get goto out; } - /* Check if we can use flow to select a queue */ - rxq = skb_get_rxhash(skb); - if (rxq) { - tap = rcu_dereference(vlan->taps[rxq % numvtaps]); - if (tap) - goto out; - } - /* Everything failed - find first available queue */ for (rxq = 0; rxq< MAX_MACVTAP_QUEUES; rxq++) { tap = rcu_dereference(vlan->taps[rxq]); --To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html