Server lag spikes at 80% -- rcu: INFO: rcu_preempt self-detected stall on CPU


New Member
Feb 13, 2024
Hello all, I just got a (new*) dell poweredge r630 for a virtualization station and was looking for a good software to run on it. I heard about how great Proxmox is and the great community behind it so I gave it a try. I installed it.

Specs (not the most impressive I know, and older hardware but I thought it would be modest enough)
Dell poweredge r630
3x960GB SSD's (RAID0)
Raid Controller - PERC H730p Mini Mono 12GB
2xIntel Xeon E5-2696 v3 (36 cores total, 72 threads)
Network Card - Broadcom BCM57800-T 2 X10GB
10GBPS Upload / Download

So far I love the rich features and UI and everything was going smoothly. But I noticed on some of my one VM during install VNC would just completely stop and lag out. Thought nothing of it. My use case for the proxmox server is all my little projects and to run a few game servers. So far I only have one VM set up.

VM Settings:
Memory: 64GB
Processors - 1 socket, 65 [host]
Machine - q35
SCSI Controller - VirtlO SCSI single

So I set up an Enshrouded to start, and its been a mess. I'll get extreme lag spikes where I'll do stuff, then everything jumps back in time 10-15 seconds. Weird. I wanted to make sure this isn't a single game related issue so I tried Palworld & minecraft instead, same thing. Extremely unstable and random lag spikes. I'm kinda scratching my head.
I installed ESXI 7 on this same setup and the issues disappeared. But I'd really like to keep using proxmox.

I'm very ignorant on where to begin my troubleshooting so I figure I'd ask here and see if there is anything I can do.

I booted up the VM and played for around 10 minutes and had multiple spikes of lag, and here's the VM graphs. Nothing outwardly jumped out at me.

Something I notice is the whole server sits at around 8% but every minute or so it spikes to 85% CPU usage , and this is when the lag starts.

Thanks for your time.

Edit: got some error codes on my console for my VM

rcu: INFO: rcu_preempt self-detected stall on CPU

rcu: 0...!: (150 GPs behind idle=cff4/0/0x1 softirq=248/248 fqs=0

rcu: rcu_preempt kthread starved for 5505 jiffies! g3041 f0x0 RCU_GP_WAIT_FQS(5 -> state 0x0 ->cpu=9

rcui: RCU grace-period kthread stack dump:

rcu: Stack dump where RCU GP kthread last ran:
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