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]);
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