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What causes sustained high CPU usage?

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Lee MacMillan

Senior Member
I have been on 388.1 since 12/9/2022. I rebooted on 2/9/2023 when the RAM usage was 852MB which was 62 days uptime. Today all 4 cores were running at 50-100% CPU when I wasn't doing anything and cores 2-4 were mostly stuck at 100%. The CPU temp was 77C when it's normally about 68-70C. I had 2 Chrome tabs open and Outlook was open. Normally CPU runs <5% on all cores. I have a very simple system, 2 wired clients and 18 or so wireless clients, most of which are idle at any given time. I rebooted and things returned to normal and RAM usage was 536MB immediately after the reboot. This has happened once before about a year ago when I was running 386.4.

So is this just one of those things that's impossible to diagnose? Would the CPU load have dropped on its own eventually? I watched it for a couple minutes before deciding to reboot. I normally open the GUI about once a week so it was just by chance that I noticed the high CPU usage. Aside from these 2 events (that I'm aware of) the router runs flawlessly. I have been using Merlin almost immediately when I got it 2 years ago.
Could be almost anything. Next time it happens SSH into the router and run top. It will show you what is using the CPU.
I must say, I'd be curious to know what you find.
I just checked my router and the CPU cores are all <5%.

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