Few GB of RAM missing on fresh install


Active Member
Nov 6, 2018
Just installed Proxmox and memory usage is showing as 1.07% (1.34 GiB of 125.84 GiB). Just wondering why it's not displaying the other 2.16GB as there's 128GB installed?

GiB not GB

Unfortunately, no. RAM is always base-2. It would actually be more complicated to construct memory modules that are not based on 2 due to things like decoding and mapping.

The "memory loss" comes from different sources:
- hardware reservation
- share of memory resources to GPU
- etc.

I've also a 128 GB machine here (similar output than you in PVE GUI) so that I can try to explain how to look at the kernel output on boot:

root@proxmox4 ~ > dmesg | grep "Memory:"
[    0.000000] Memory: 131910836K/134215624K available (12300K kernel code, 2480K rwdata, 4288K rodata, 2420K init, 2416K bss, 2304788K reserved, 0K cma-reserved)

The maximum available 134215624K is almost exactly 128 GiB:

(134215624 + 2104 ) / 1024.0 / 1024.0

The correction factor of 2104 comes probably from further hardware reservations and memory mappings. The lower value was a start value and there are further "freeing" messages logged in my dmesg so that this number increased eventually to:

root@proxmox4 ~ > grep MemTotal /proc/meminfo
MemTotal:       132018096 kB

Which is 125.90 GiB, also similar to your value.
Same here...
any idea/resolution?
The Linux kernel reserves some memory to administer the available memory. This administration takes a few percent of the memory and when you have hundreds of GB's of memory, that means that a few GB is not available.
Also, some memory is reserved per CPU and with more cores today, it also becomes noticeable. I have 16 cores but my BIOS says that 32 is possible, so I can get a little memory back with this possible_cpus=16 kernel parameter.
All in all, there is not much you can do: it takes memory to manage memory.


The Proxmox community has been around for many years and offers help and support for Proxmox VE, Proxmox Backup Server, and Proxmox Mail Gateway.
We think our community is one of the best thanks to people like you!

Get your subscription!

The Proxmox team works very hard to make sure you are running the best software and getting stable updates and security enhancements, as well as quick enterprise support. Tens of thousands of happy customers have a Proxmox subscription. Get yours easily in our online shop.

Buy now!