# Akka - low CPU usage (could my code go faster?) **URL:** \ **Category:** Akka Libraries\ **Tags:** scala, configuration\ **Created:** [September 4, 2020, 6:43am UTC](https://discuss.akka.io/t/akka-low-cpu-usage-could-my-code-go-faster/7112 "2020-09-04T06:43:50Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![jst](https://avatars.discourse-cdn.com/v4/letter/j/edb3f5/32.png) [@jst](https://discuss.akka.io/u/jst)\ **Post date:** [September 4, 2020, 6:43am UTC](https://discuss.akka.io/t/akka-low-cpu-usage-could-my-code-go-faster/7112/1 "2020-09-04T06:43:50Z")
Hi guys, I’ve got the following problem. I’ve got a network of ~100 Actors, all running locally. The code is more or less: There is one Actor “network” and 100 “nodes” `network` sends `step` to all the nodes upon receiving `step` node sends `data` to it’s neighbours upon receiving `data` node does some calculation on it, and adds the sender to `seen` set. If all the neighbours are seen it sends `ready` to network upon receiving `ready` network adds node to `seen`. If all are seen new `step` is sent. My problem: while the code runs and with debug enabled I can see a lot of messages is being sent, the JVM process utilizes between 0.5 and 1% of my CPU. Memory should not be a problem as well as the JVM consumes 700-900MB of Ram and Xmxx is set to 4G. There are no disk writes. What is my bottleneck? Why won’t my code use more CPU to run faster? I’m new to Akka but my suspicion is that the dispatcher might tick not frequently enough? Could that be a thing? ---
**Author:** ![raboof](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.akka.io/raboof/32/2913_2.png) [@raboof](https://discuss.akka.io/u/raboof)\ **Post date:** [September 4, 2020, 12:34pm UTC](https://discuss.akka.io/t/akka-low-cpu-usage-could-my-code-go-faster/7112/2 "2020-09-04T12:34:11Z")
> [@jst](#): > > my suspicion is that the dispatcher might tick not frequently enough? Could that be a thing? Not really: the dispatcher threads should immediately continue processing further work when there is any available. Are you doing any blocking calls as part of the actor message processing? Perhaps you can share the project somewhere? ---
**Author:** ![jst](https://avatars.discourse-cdn.com/v4/letter/j/edb3f5/32.png) [@jst](https://discuss.akka.io/u/jst)\ **Post date:** [September 4, 2020, 12:39pm UTC](https://discuss.akka.io/t/akka-low-cpu-usage-could-my-code-go-faster/7112/3 "2020-09-04T12:39:13Z")
It can be viewed on [my repo](https://github.com/jstawik/WUST-DNA/) - beware though, as I’m new to Akka this is probably as hot garbage as it gets 🙂 I’m currently running `ACDemo` class from [Simulator.scala](https://github.com/jstawik/WUST-DNA/blob/master/src/main/scala/Simulator.scala) which is my entry point ---
**Author:** ![raboof](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.akka.io/raboof/32/2913_2.png) [@raboof](https://discuss.akka.io/u/raboof)\ **Post date:** [September 4, 2020, 1:37pm UTC](https://discuss.akka.io/t/akka-low-cpu-usage-could-my-code-go-faster/7112/4 "2020-09-04T13:37:28Z")
One thing that could be problematic is the `Await.result` in `Network.scala`: that could lead to trouble later, since it blocks the dispatcher and may lead to dispatcher exhaustion. That might not be so easy to refactor. An important question here is: do these nodes really need to be actors, or could they be ‘regular’ objects inside the Network actor? To determine that I guess the question is if there’s ever another actor than the network that’s talking to the nodes - for example do they ever directly talk to each other? When you run into this, you’d expect taking a `jstack` stack trace of your application would show a bunch of dispatcher threads in the `Await.result` function, though, and I don’t think I see that, so there might be something else going on first. Without diving into the code further I don’t think I see what is causing the lack of progress here, though. ---
**Author:** ![jst](https://avatars.discourse-cdn.com/v4/letter/j/edb3f5/32.png) [@jst](https://discuss.akka.io/u/jst)\ **Post date:** [September 4, 2020, 1:42pm UTC](https://discuss.akka.io/t/akka-low-cpu-usage-could-my-code-go-faster/7112/5 "2020-09-04T13:42:50Z")
Good lead - I was refactoring `Await`s out earlier, must have left this one in by accident. Will work on it soon. The Actors do talk to each other - when receiving `step` from network they send data to each other an process it. Will try getting rid of `Await` and report back ---
**Author:** ![jst](https://avatars.discourse-cdn.com/v4/letter/j/edb3f5/32.png) [@jst](https://discuss.akka.io/u/jst)\ **Post date:** [September 4, 2020, 7:40pm UTC](https://discuss.akka.io/t/akka-low-cpu-usage-could-my-code-go-faster/7112/6 "2020-09-04T19:40:28Z")
Reporting back 🙂 I did pushed the `Await` to a part of code that’s within a `Future[Unit]` that is called at the very end of my program and is called in “fire and forget” fashion, but I still don’t get CPU usages higher than 1%. Any other ideas? Suggestions as how I could try to find the bottleneck? (I’m assuming one exists, because if CPU is running almost IDLE it means something else must be stopping the execution) ~~One thing I was able to find in Java Mission Control: the Peak Live Thread Count is 54, but most of the time 13-14 threads are being used, and I can’t figure out when did the peak happen (see attached screen shot). My machine is a 8core/16threads one.~~ ![jmc_L5U3jHdjEo](https://us1.discourse-cdn.com/flex020/uploads/discuss_lightbend/original/2X/8/814ff87369e4329ca48eeeb8a3107c0584f70296.png) The peak occurs at the beginning. I did some profiling with JVisualVM and it’s apparent for me that the threads are mainly waiting: ![java_oyLXGubQXj](https://us1.discourse-cdn.com/flex020/uploads/discuss_lightbend/original/2X/6/6de91f32b75ad2766af2d7c5d5d6e6d615f37090.png) I need to figure out why they are waiting though - the code executed shouldn’t be blocking - the logic is entirely driven by firing messages - an actor receives a message, computes, fires a message. The only thing I can think of is the synchronization being done by checking if all reported - there will be moments, where a lot of nodes in the network will be done and have sent all reported, but those won’t receive any messages then, so shouldn’t affect the threads, right?