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My IIS server running on Azure VM is having occasionally high cpu usage. It happens only on Thursdays, Fridays or Saturdays between 11 AM - 2 PM. CPU usage is 100% and cannot do anything on VM. I can only force shutdown. Even force shutdown takes more than 15 minutes to stop vm in that state. I cannot reproduce the issue.

I have over 300 applications on my IIS 10 on Windows 2022 DataCenter. The inbound calls are quite low. Getting max like 20-30 requests per second. I have more than enough ram. Daily usage doesnt surpass 60% of my RAM. Daily use of cpu doesnt surpass 30%. Note that on same vm I also have MSSQL server. When high cpu happens then I can clearly see that its IIS fault. Whenever I stop it, everything runs normal. I had occasions where I restarted once or twice vm and everything was working normal again for some reason. I observed that on the day of high cpu usage even if only 2-3 clients are using server I see that moving mouse or moving windows in vm through RDP is sluggish. On normal day it works pretty fast. Maybe its some kind of hint related to networking?

What I tried so far to fix issue:

  1. Optimize code - I havent found any memory leaks or flaw using profiling tools
  2. Disable firewall and antivirus - it didn't do much
  3. Buy more RAM and more CPU - still no help
  4. Limit IIS apps to only 3 apps by renaming folder of other IIS apps that I want to block so that my clients wont access app - it somehow helped cpu usage was lower around 30-40% but still the vm that I accessed by RDP was running slow. By slow I mean moving mouse was lagging and moving windows around was sluggish.
  5. Track high cpu usage by Azure app insights and new relic - no help they both show that there was no high cpu usage. Although they tracked that there was a downtime during malfunction.
  6. Ask Azure support for help - they have run diagnostics and according to them everything works fine they didnt found any issues
  7. Buy better and faster disks - no help

Is there anything more that I can do to track what is the actual problem with my high cpu usage?

user2279379
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0 Answers0