A lot of the above graphs are from ProxMox. I just started using it yesterday, after having lots of trouble with corruption using VirtualBox. Like others, I noticed that HA is taking up lots of memory, according to Proxmox.
Which add on are you using to display the percentage?
I dont find the memory usage percentage 
in system monitor there isn’t the options to activate it.
Do you mean sensor memory usage for individual addons or system? Im using glances addon for monitoring, and glances integration for sensors. But with built in System monitor integration the sensor for memory usage its there too
memory usage yes, but not the memory usage percentage, the one that I need
I’ve noticed this exact same behavior. I have an automation to inform me if memory breaches a threshold. I’ve had it for a very long time and it has never triggered but in the past month or so it has triggered after updates. Like him noticing that after rebooting the memory normalizes. This is absolutely new behavior. I have no idea what causes it, it seems benign only because we can reboot to clear it but it is certainly concerning
I’m still not fully understanding what this means.
See my example, just upgraded from 6GB to 8GB memory, obvious in this graph
Output TOP command (after allocating 8GB)
HA System monitor (before and after 8 GB)
From an HA system monitor perspective it seemed there is/was enough memory available (even when I ran with 6GB). However, from the top command I see now (with 8GB enabled!) about only 1.6 free.
The HA system monitor appears the exclude the buff/cache as being used, right?
The proxmox graph also shows that the system wants/needs a bit more memory as it now takes more now 8GB is available. (why did it not do that before and still left some to spare?). Any explanations?
Or will it simply allocate more cache if it’s available?
Secondly, 6GB of active usage sounds like a lot. I do have a large system but is this abnormal? What are the big memory consumers in HA?
You can not use the monitoring in Proxmox.
The VM will use memory for cache, which it can release quickly, should it be needed.
In Proxmox it will just be seen as used memory.