this post was submitted on 03 Mar 2026
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qemu/kvm memory question (programming.dev)
submitted 3 days ago by transporter_ii@programming.dev to c/linux4noobs@programming.dev
6 comments fedilink hide all child comments
 

Moved to Mint months back. I had to install Win10 in a kvm for a couple of things impossible on Linux. I allocated 16 gig of ram to the kvm. I can't really find anything on how that works, exactly. According to Stacer, I have a consistent 16 gig of ram being used, but that's between a running Win10 kvm and all of my other running Linux programs. I've never seen my system memory use move higher or lower than 16 gig of ram when the vm is running. Again, that's the kvm + normal Linux programs.

If I allocated 16 gig of ram to the kvm, shouldn't my memory usage be over 16 gig or ram with other Linux programs running?

About once a week, maybe two weeks, I open a new tab on a browser and it hangs my system. Nothing works but the mouse pointer.

I initially thought of a memory leak with Firefox, but it will also do it opening a new tab in Chrome.

The last time it hung up, I think I noticed the virtual machine manager icon was missing from the menu bar. I'm waiting for it to hang up again to verify this.

Anyone have any thoughts on this?

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[–] refalo@programming.dev 1 points 3 days ago* (last edited 3 days ago) (1 children)

If I allocated 16 gig of ram to the kvm, shouldn’t my memory usage be over 16 gig or ram with other Linux programs running?

Normally yes, in my experience.

I open a new tab on a browser and it hangs my system

Hangs the host or the VM guest?

If it's the host, does it ever happen when the VM isn't running?

If it's the guest, are you sure the VM itself isn't just paused? One thing I have noticed is that the VM will pause when either I run out of disk space, or (if using -snapshot) run out of RAM (because it's using RAM as an always-expanding disk image).

[–] transporter_ii@programming.dev 1 points 3 days ago (1 children)

I have a pc that's only a few months old, wiped, and with a pretty much default install of LM. I have 32 gig of ram. Unless there is something about Stacer I don't understand, it always shows half of the ram used (when I have the vm running). The graph never moves. I pretty much always have the vm running, because I absolutely have to have Windows with an IIS server on it (work related).

The entire system hangs. The only way I can recover is to reboot. The screen freezes, but the mouse pointer still moves around. I can click on things, but it does nothing. The keyboard does nothing.

I'm pretty bad about keeping a lot of tabs open in a couple of browsers. Almost every time it hangs involves opening a new tab in Firefox or Chromium. Sometimes youtube is involved, but I don't think every single time does.

Like I said, the last time it hung, I just happened to notice that the vm manager icon had disappeared from the menu bar, like it had exited when it hung. I'm going to check for that the next time it hangs.

Luckily, it only hangs about once every week or so. Lately, it has been going almost two weeks. It's really not that big a deal, but it would suck if it was doing it every few days.

Thanks,

[–] refalo@programming.dev 1 points 3 days ago* (last edited 3 days ago) (2 children)

Have you checked dmesg (or historical system boot logs) and also ran memtest86+ to make sure your RAM isn't faulty? Even if it's brand new it can still happen. If you have another system nearby (or even just a phone) you could try to SSH (make sure to enable/start the daemon before it freezes) into the machine and see if it's still responsive.

I had a similar issue where I'd get a full system freeze every few weeks (not even the mouse worked), and that one turned out to be a faulty cpu, it was the infamous Raptor Lake "Vmin shift instability" bug, which I got replaced under warranty and that fixed the issue.

But since your mouse still works, we know your CPU is still functioning.

Have you tried to switch to the console with Ctrl+Alt+F1 (or F2 etc.) when the freeze happens? It could just be a software bug with your graphical environment (either Xorg/wayland or your particular window manager/desktop environment like KDE/Gnome/etc.) since the kernel itself doesn't appear to be locked up if the mouse still works.

[–] transporter_ii@programming.dev 1 points 17 hours ago (1 children)

So, it just froze on me about 10 minutes ago. I can drop to the console. The vm manager icon did not disappear from the menu bar, so I was wrong about that. Everything freezes. I cannot interact with any browser or any app. The mouse pointer did change from a pointer to hand over a link or something at one point, but never changed back. After dropping to the console, I eventually just had to reboot and restart everything. The best way to describe it is, someone replaced my desktop with an image, and the only thing that still works is moving the mouse around.

I'm thinking it's been about a week or so since it did this last. Oh, and I was poking around on a web page when it did it. Web browsers are always involved, but not specifically any one browser.

[–] refalo@programming.dev 1 points 12 hours ago

If you can still switch to the console, then check dmesg and/or journalctl -eb for any issues. But this at least tells you the system itself is not frozen. The kernel still works.

I would try to restart your login manager/desktop environment and see if that brings you back to a working desktop. If so then it sounds like a software bug in your DE. You could try switching to a different one and see if that helps anything. As a last resort you could also try a completely different Linux distro.

[–] transporter_ii@programming.dev 1 points 2 days ago* (last edited 2 days ago)

Have you checked dmesg (or historical system boot logs) and also ran memtest86+ to make sure your RAM isn’t faulty? Even if it’s brand new it can still happen. If you have another system nearby (or even just a phone) you could try to SSH (make sure to enable/start the daemon before it freezes) into the machine and see if it’s still responsive.

I have poked around in logs a little. Nothing has jumped out at me. I'll test the memory and turn SSH on. I used Ubuntu on the desktop for about 8 - 10 years, and then swapped back to Windows ~2018 for work. I used to mess with hardware a lot, but I've fried my brain programming for too many years now.

I do see reports of Linux Mint hanging with nothing but the mouse working, but nothing has jumped out at me as a fix. The reports are going back a while, too. A lot of comments say it is something with the graphics card.

My new pc is a: HP OmniDesk Desktop Computer PC, AMD Ryzen 7 8700G, 32GB DDR5 Memory, 1TB NVMe SSD, Radeon 780M Graphics

Outside of this one issue, it's a beast with Linux on it (I'm not a gamer, though). I bought it right before RAM prices jacked the prices of everything up.