OPC UA Client and high CPU|OPC UA Standard|Forum|OPC Foundation

Hi people,

We are currently running tests with our OPC UA client application that talks to remotes PLCs that contains roughly 3000 tags. In our client app, all 3000 monitored are distributed over 4 subscriptions and their values moves a lot and we expect some CPU activity. But we read actually like 75-80% constant CPU usage on the Client PC (in fact it take all remaining system CPU that rise in the task manager at 100) and we try to figure out what is going wrong. The sampling interval is at 1000 ms (for subscription and monitored items) but has we increase the subscription sampling to 10000 ms, then we can see the CPU drop to 1% and peak at 30-35% every 9-10 seconds. The value updates seems also inconsistent, probably due to the CPU usage.

I have no clue at all what can cause this behavior. At one subscription with 1000 tags, the CPU is at 4-5% and it works a bit better. And most important, if I subscribe all 3000 tags but I skip the notification += event on all monitored items, then I notice the same High CPU behavior.

configurations (items):

MonitoredItem monitoredItem = new MonitoredItem(subscription.DefaultItem)
{
StartNodeId = nodeId,
AttributeId = Attributes.Value,
DisplayName = (string)nodeId.Identifier,
MonitoringMode = MonitoringMode.Reporting,
SamplingInterval = 1000,
QueueSize = 1,
DiscardOldest = true
};
monitoredItem.Handle = new ItemInfo(tag);  // our custom object linked to

// add the callback notification event
monitoredItem.Notification += MonitoredItemEvents;

configurations (subscription):

subscription = new Subscription(m_session.DefaultSubscription)
{
PublishingEnabled = true,
PublishingInterval = 1000,
MaxMessageCount = 1000,
MaxNotificationsPerPublish = 1000
};
subscription.KeepAliveCount = 10;
subscription.LifetimeCount = 10;
subscription.Priority = 0;

m_session.AddSubscription(subscription);
subscription.Create();

configurations (xml config file):

<TransportQuotas>
<OperationTimeout>600000</OperationTimeout>
<MaxStringLength>1048576</MaxStringLength>
<MaxByteStringLength>1048576</MaxByteStringLength>
<MaxArrayLength>65535</MaxArrayLength>
<MaxMessageSize>4194304</MaxMessageSize>
<MaxBufferSize>65535</MaxBufferSize>
<ChannelLifetime>300000</ChannelLifetime>
<SecurityTokenLifetime>3600000</SecurityTokenLifetime>
</TransportQuotas>

<ClientConfiguration>
<DefaultSessionTimeout>60000</DefaultSessionTimeout>
<WellKnownDiscoveryUrls>
<ua:String>opc.tcp://{0}:4840</ua:String>
<ua:String>http://{0}:52601/UADiscovery</ua:String>
<ua:String>http://{0}/UADiscovery/Default.svc</ua:String>
</WellKnownDiscoveryUrls>
<DiscoveryServers></DiscoveryServers>
<EndpointCacheFilePath>Endpoints.xml</EndpointCacheFilePath>
<MinSubscriptionLifetime>10000</MinSubscriptionLifetime>
</ClientConfiguration>

So if you have any information regarding this subject, it would be very helpful.

Thank you,