mono-sgen using way too much CPU (even when not in use)


Having Rider open for any period of time results in multiple mono-sgen instances spawning and eating up the majority of my CPU.  The attached screenshot is me not touching rider for a good 10 minutes and it just chews threw CPU in the background.  This happens on both my home and work computers running macOS 10.12 with the latest RC.  If I close Rider it successfully cleans up the processes but they come back quickly after reopening.



It seems I spoke too soon.  When closing Rider it sometimes cleans up all of the mono-sgen processes.



Thanks for the feedback! This bug is already fixed in RTM which will be released very soon.
Plese find more information here:



It was is still there :(


It's definitely still there

JetBrains Rider 2018.2.3
Build #RD-182.4231.496, built on September 13, 2018
JRE: 1.8.0_152-release-1248-b8 x86_64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
macOS 10.13.6


Could you please check the latest EAP build? Is it better? We've fixed several performance issues in Rider 2018.3.


Yes, with the latest EAP on Ubuntu 18.04 this issue still exists, doesn't clean up, and way too much CPU/Memory usage.


Josh Taylor

Could you please collect a thread dump on Rider 2018.3. EAP when CPU/memory usage runs high (Help -> Create Backend Thread Dump)? Please attach it to a new support request.


This is still a problem in 2019.1 EAP FYI


Anders Rørvik, 

Are there any repro steps that cause the high CPU usage? Could you possibly collect a Backend Thread Dump as described in my previous message?


I have the same issue as Anders Rørvik, though intermittently. Will try to get a thread dump. Version:

JetBrains Rider 2019.1 EAP
Build #RD-191.6733.764, built on April 19, 2019
Rider EAP User
Expiration date: May 19, 2019
JRE: 1.8.0_202-release-1483-b49 amd64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Linux 5.0.0-13-generic


I have the same issue.

JetBrains Rider 2019.1
Build #RD-191.6733.943, built on April 29, 2019
JRE: 1.8.0_202-release-1483-b49 x86_64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
macOS 10.14.4

Steps to reproduce:

  • Open solution (Solution with 2 .net core 2.2 console projects)
  • Select a project and click "Advanced Build Actions > Rebuild Selected Projects with Diagnostics" 

I'm running into same issue. Was happening with Rider 2019.1.1
Was hoping 2019.1.2 would fix it but it hasn't.


JetBrains Rider 2019.1.2
Build #RD-191.7141.355, built on June 5, 2019
JRE: 1.8.0_202-release-1483-b58 x86_64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
macOS 10.14.4


My laptop gets very warm (and fans get loud) which is very unusual for my macbook.

Please advise. 


Same issue as @Kresimir described. Same version, same OSx... My macbook pro just burning after CODING, and when I Play Unity scene that become unusable at all - lagging like a hell. Now I seriously start to think about migrating to another IDE. After year of Rider subscription general feeling is disappointing. 

For everyone who experiences the same problem, update mono framework. I have removed it completely (follow instruction on official website) and install latest available. Now mono-sgen activity takes up to 10% even with enabled  Wide analysys.


Hi everyone! 

As Romans said, please, try to update both Rider and mono to the latest version.

If this won't help, we need a thread dump on Rider 2019.2 when CPU/memory usage runs high (Help -> Create Backend Thread Dump). Please attach it to a new support request.

Thank you all! 


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