[ovs-dev] [PATCH v3 1/4] dpif-netdev: Skip EMC lookup/insert for recirc packets
antonio.fischetti at intel.com
antonio.fischetti at intel.com
Fri Aug 11 15:52:43 UTC 2017
When OVS is configured as a firewall, with thousands of active
concurrent connections, the EMC gets quicly saturated and may
come under heavy thrashing for the reason that original and
recirculated packets keep overwriting the existing active EMC
entries due to its limited size (8k).
This thrashing causes the EMC to be less efficient than the dcpls
in terms of lookups and insertions.
This patch allows to use the EMC efficiently by allowing only
the 'original' packets to hit EMC. All recirculated packets are
sent to the classifier directly.
An empirical threshold EMC_RECIRCT_NO_INSERT_THRESHOLD - of 50% -
for EMC occupancy is set to trigger this logic. By doing so when
EMC utilization exceeds EMC_RECIRCT_NO_INSERT_THRESHOLD:
- EMC Insertions are allowed just for original packets.
EMC insertion and look up are skipped for recirculated packets.
- Recirculated packets are sent to the classifier.
This patch is based on patch
"dpif-netdev: add EMC entry count and %full figure to pmd-stats-show" at:
https://mail.openvswitch.org/pipermail/ovs-dev/2017-January/327570.html
CC: Jan Scheurich <jan.scheurich at ericsson.com>
Signed-off-by: Antonio Fischetti <antonio.fischetti at intel.com>
Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy at intel.com>
Co-authored-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy at intel.com>
---
Connection Tracker testbench set up with
table=0, priority=1 actions=drop
table=0, priority=10,arp actions=NORMAL
table=0, priority=100,ct_state=-trk,ip actions=ct(table=1)
table=1, ct_state=+new+trk,ip,in_port=1 actions=ct(commit),output:2
table=1, ct_state=+est+trk,ip,in_port=1 actions=output:2
table=1, ct_state=+new+trk,ip,in_port=2 actions=drop
table=1, ct_state=+est+trk,ip,in_port=2 actions=output:1
2 PMDs, 3 Tx queues.
I measured packet Rx rate (regardless of packet loss). Bidirectional
test with 64B UDP packets.
Each row is a test with a different number of traffic streams. The traffic
generator is set so that each stream establishes one UDP connection.
Mpps columns reports the Rx rates on the 2 sides.
I set up the generator to loop on the dest IP addr on one side,
and loop instead on the source IP addr on the other side.
For example to generate 10 different flows, I was sending to phy port #1
UDP, IPsrc:10.10.10.10, IPdest: 20.20.20.[20-29], PortSrc: 63, PortDest: 63
Instead to phy port #2 (source and dest IPs are now swapped):
UDP, IPsrc: 20.20.20.[20-29], IPdest: 10.10.10.10, PortSrc: 63, PortDest: 63
I saw the following performance improvement.
Original OvS-DPDK means at Commit ID:
6b1babacc3ca0488e07596bf822fe356c9bab646
+----------------------+-----------------------+
| Original OvS-DPDK | Original OvS-DPDK |
| | + this patch |
---------+------------+---------+------------+----------+
Traffic | Rx | EMC | Rx | EMC |
Streams | [Mpps] | entries | [Mpps] | entries |
---------+------------+---------+------------+----------+
100 | 2.43, 2.49 | 200 | 2.55, 2.57 | 201 |
1,000 | 2.01, 2.02 | 2007 | 2.12, 2.12 | 2006 |
2,000 | 1.93, 1.95 | 3868 | 1.98, 1.96 | 3884 |
3,000 | 1.87, 1.91 | 5086 | 1.97, 1.97 | 4757 |
4,000 | 1.83, 1.82 | 6173 | 1.94, 1.93 | 5280 |
10,000 | 1.67, 1.69 | 7826 | 1.82, 1.81 | 7090 |
30,000 | 1.57, 1.59 | 8192 | 1.66, 1.67 | 8192 |
---------+------------+---------+------------+----------+
This test setup implies 1 recirculation on each received packet.
We didn't check this patch in a test scenario where more than 1
recirculation is occurring per packet.
---
lib/dpif-netdev.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 61 insertions(+), 4 deletions(-)
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index bea1c3f..8f6b96b 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -4663,6 +4663,9 @@ dp_netdev_queue_batches(struct dp_packet *pkt,
packet_batch_per_flow_update(batch, pkt, mf);
}
+/* Threshold to skip EMC for recirculated packets. */
+#define EMC_RECIRCT_NO_INSERT_THRESHOLD 0xFFFFF000
+
/* Try to process all ('cnt') the 'packets' using only the exact match cache
* 'pmd->flow_cache'. If a flow is not found for a packet 'packets[i]', the
* miniflow is copied into 'keys' and the packet pointer is moved at the
@@ -4714,8 +4717,36 @@ emc_processing(struct dp_netdev_pmd_thread *pmd,
key->len = 0; /* Not computed yet. */
key->hash = dpif_netdev_packet_get_rss_hash(packet, &key->mf);
- /* If EMC is disabled skip emc_lookup */
- flow = (cur_min == 0) ? NULL: emc_lookup(flow_cache, key);
+ /*
+ * EMC lookup is skipped when one or both of the following
+ * two cases occurs:
+ *
+ * - EMC is disabled. This is detected from cur_min.
+ *
+ * - The EMC occupancy exceeds EMC_RECIRCT_NO_INSERT_THRESHOLD and
+ * the packet to be classified is being recirculated. When this
+ * happens also EMC insertions are skipped for recirculated
+ * packets. So that EMC is used just to store entries which
+ * are hit from the 'original' packets. This way the EMC
+ * thrashing is mitigated with a benefit on performance.
+ */
+ if (OVS_LIKELY(cur_min)) {
+ if (!md_is_valid) {
+ flow = emc_lookup(flow_cache, key);
+ } else {
+ /* Recirculated packet. */
+ if (flow_cache->n_entries & EMC_RECIRCT_NO_INSERT_THRESHOLD) {
+ /* EMC occupancy is over the threshold. We skip EMC
+ * lookup for recirculated packets. */
+ flow = NULL;
+ } else {
+ flow = emc_lookup(flow_cache, key);
+ }
+ }
+ } else {
+ flow = NULL;
+ }
+
if (OVS_LIKELY(flow)) {
dp_netdev_queue_batches(packet, flow, &key->mf, batches,
n_batches);
@@ -4800,7 +4831,20 @@ handle_packet_upcall(struct dp_netdev_pmd_thread *pmd,
add_actions->size);
}
ovs_mutex_unlock(&pmd->flow_mutex);
- emc_probabilistic_insert(pmd, key, netdev_flow);
+ /* EMC insertion can be skipped by a probabilistic criteria or
+ * - in case of recirculated packets - depending on the number of
+ * EMC entries. */
+ if (!packet->md.recirc_id) {
+ emc_probabilistic_insert(pmd, key, netdev_flow);
+ } else {
+ /* Recirculated packets. When EMC occupancy goes over
+ * a threshold we avoid inserting new entries. */
+ if (!(pmd->flow_cache.n_entries &
+ EMC_RECIRCT_NO_INSERT_THRESHOLD)) {
+ /* Still under the threshold. */
+ emc_probabilistic_insert(pmd, key, netdev_flow);
+ }
+ }
}
}
@@ -4893,7 +4937,20 @@ fast_path_processing(struct dp_netdev_pmd_thread *pmd,
flow = dp_netdev_flow_cast(rules[i]);
- emc_probabilistic_insert(pmd, &keys[i], flow);
+ /* EMC insertion can be skipped by a probabilistic criteria or
+ * - in case of recirculated packets - depending on the number of
+ * EMC entries. */
+ if (!packet->md.recirc_id) {
+ emc_probabilistic_insert(pmd, &keys[i], flow);
+ } else {
+ /* Recirculated packets. When EMC occupancy goes over
+ * a threshold we avoid inserting new entries. */
+ if (!(pmd->flow_cache.n_entries &
+ EMC_RECIRCT_NO_INSERT_THRESHOLD)) {
+ /* Still under the threshold. */
+ emc_probabilistic_insert(pmd, &keys[i], flow);
+ }
+ }
dp_netdev_queue_batches(packet, flow, &keys[i].mf, batches, n_batches);
}
--
2.4.11
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