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netdev-dpdk: Reset RSS hash on transmit

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When using DPDK rings (dpdkr port type), packet buffers get shared
to consumers of the rings (e.g. Virtual Machines). The packet buffers
also include the RSS hash. This is a hash of a number of fields
in the packet and is used in order to do a fast lookup in the EMC.

However, if a consumer of the packet modifies the packet without
regenerating the RSS hash, the EMC will use the same hash for lookup
even though the packet may belong to a different flow. This would
cause unnecessary collisions in the EMC reducing performance in the
presence of multiple flows.

To avoid receiving an incorrect RSS hash on reception from a DPDK
ring, the RSS hash needs to be reset on transmission. This will reduce
performance of the forwarding path as the RSS hash will need to
calculated for every packet received from an dpdkr but will behave
correctly in the presence of a large number of flows that get
modified by the consumer of a DPDK ring

Signed-off-by: Mark D. Gray <mark.d.gray@intel.com>
Acked-by: Daniele Di Proietto <diproiettod@vmware.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
This commit is contained in:
Mark D. Gray
2015-04-13 06:36:56 -07:00
committed by Pravin B Shelar
parent 5e65e080ad
commit 1b99bb0552
1 changed files with 22 additions and 12 deletions
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34
lib/netdev-dpdk.c
View File

@@ -558,11 +558,11 @@ netdev_dpdk_init(struct netdev *netdev_, unsigned int port_no,
netdev_->n_rxq = NR_QUEUE;
if (type == DPDK_DEV_ETH) {
netdev_dpdk_alloc_txq(netdev, NR_QUEUE);
err = dpdk_eth_dev_init(netdev);
if (err) {
goto unlock;
}
netdev_dpdk_alloc_txq(netdev, NR_QUEUE);
err = dpdk_eth_dev_init(netdev);
if (err) {
goto unlock;
}
}
list_push_back(&dpdk_list, &netdev->list_node);
@@ -906,10 +906,10 @@ __netdev_dpdk_vhost_send(struct netdev *netdev, struct dp_packet **pkts,
int tx_pkts, i;
if (OVS_UNLIKELY(!is_vhost_running(virtio_dev))) {
ovs_mutex_lock(&vhost_dev->mutex);
vhost_dev->stats.tx_dropped+= cnt;
ovs_mutex_unlock(&vhost_dev->mutex);
goto out;
ovs_mutex_lock(&vhost_dev->mutex);
vhost_dev->stats.tx_dropped+= cnt;
ovs_mutex_unlock(&vhost_dev->mutex);
goto out;
}
/* There is vHost TX single queue, So we need to lock it for TX. */
@@ -923,9 +923,9 @@ __netdev_dpdk_vhost_send(struct netdev *netdev, struct dp_packet **pkts,
out:
if (may_steal) {
for (i = 0; i < cnt; i++) {
dp_packet_delete(pkts[i]);
}
for (i = 0; i < cnt; i++) {
dp_packet_delete(pkts[i]);
}
}
}
@@ -1064,6 +1064,7 @@ netdev_dpdk_send__(struct netdev_dpdk *dev, int qid,
for (i = 0; i < cnt; i++) {
int size = dp_packet_size(pkts[i]);
if (OVS_UNLIKELY(size > dev->max_packet_len)) {
if (next_tx_idx != i) {
dpdk_queue_pkts(dev, qid,
@@ -1745,6 +1746,15 @@ netdev_dpdk_ring_send(struct netdev *netdev, int qid OVS_UNUSED,
struct dp_packet **pkts, int cnt, bool may_steal)
{
struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
unsigned i;
/* When using 'dpdkr' and sending to a DPDK ring, we want to ensure that the
* rss hash field is clear. This is because the same mbuf may be modified by
* the consumer of the ring and return into the datapath without recalculating
* the RSS hash. */
for (i = 0; i < cnt; i++) {
dp_packet_set_rss_hash(pkts[i], 0);
}
/* DPDK Rings have a single TX queue, Therefore needs locking. */
rte_spinlock_lock(&dev->txq_lock);