diff mbox series

[ovs-dev,RFC,16/26] dpif-netdev: Quiesce offload thread periodically

Message ID 2eb0e7ba586aff40e1a98f42459dc3d6ae08cb7c.1607177117.git.grive@u256.net
State RFC
Headers show
Series [ovs-dev,RFC,01/26] netdev: Add flow API de-init function | expand

Commit Message

Gaetan Rivet Dec. 5, 2020, 2:22 p.m. UTC 
After each processed offload, the offload thread currently quiesce and
will sync with RCU. This synchronization can be lengthy and make the
thread unnecessary slow.

Instead attempt to quiesce every 10 ms at most or any time the queue is
empty.

Signed-off-by: Gaetan Rivet <grive@u256.net>
---
 lib/dpif-netdev.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 1bbe6d98f..6a3413b2e 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -2735,15 +2735,20 @@  err_free:
     return -1;
 }
 
+#define DP_NETDEV_OFFLOAD_QUIESCE_INTERVAL_US (10 * 1000) /* 10 ms */
+
 static void *
 dp_netdev_flow_offload_main(void *data OVS_UNUSED)
 {
     struct dp_offload_thread_item *offload;
     struct ovs_list *list;
     long long int latency_us;
+    long long int next_rcu;
+    long long int now;
     const char *op;
     int ret;
 
+    next_rcu = time_usec() + DP_NETDEV_OFFLOAD_QUIESCE_INTERVAL_US;
     for (;;) {
         ovs_mutex_lock(&dp_offload_thread.mutex);
         if (ovs_list_is_empty(&dp_offload_thread.list)) {
@@ -2751,6 +2756,7 @@  dp_netdev_flow_offload_main(void *data OVS_UNUSED)
             ovs_mutex_cond_wait(&dp_offload_thread.cond,
                                 &dp_offload_thread.mutex);
             ovsrcu_quiesce_end();
+            next_rcu = time_usec() + DP_NETDEV_OFFLOAD_QUIESCE_INTERVAL_US;
         }
         list = ovs_list_pop_front(&dp_offload_thread.list);
         dp_offload_thread.enqueued_item--;
@@ -2774,14 +2780,22 @@  dp_netdev_flow_offload_main(void *data OVS_UNUSED)
             OVS_NOT_REACHED();
         }
 
-        latency_us = time_usec() - offload->timestamp;
+        now = time_usec();
+
+        latency_us = now - offload->timestamp;
         mov_avg_ema_update(&dp_offload_thread.ema, latency_us);
 
         VLOG_DBG("%s to %s netdev flow "UUID_FMT,
                  ret == 0 ? "succeed" : "failed", op,
                  UUID_ARGS((struct uuid *) &offload->flow->mega_ufid));
         dp_netdev_free_flow_offload(offload);
-        ovsrcu_quiesce();
+
+        /* Do RCU synchronization at fixed interval. */
+        if (now > next_rcu) {
+            if (!ovsrcu_try_quiesce()) {
+                next_rcu += DP_NETDEV_OFFLOAD_QUIESCE_INTERVAL_US;
+            }
+        }
     }
 
     return NULL;