.

The current Linux tasks on my Ryzen seem to max out at less than 2GB/task but by the time you count overheads, I would agree 3GB/task is about right.

My measurements indicate that the working set size gets up to 1.4 GBytes in size near the end of processing, but 1.3 GBytes the rest of the time. The virtual apace required is a little more, but I think it unfair to count that as it can be paged out if the OS needs more RAM. But the difference is really not worth quibbling about.

On my Linux machine, they max out at about 1.4 g 2.2% MEM, and those are only very late in their execution.
The hadam4_um_8.52 tasks are the N216 models. My machine is #1511241.

  
RES       SHR    %MEM    %CPU  P     TIME+     COMMAND                                                                                                                    
   1.3g  19892   2.1     99.1  7    926:37.95 /var/lib/boinc/projects/climateprediction.net/hadam4_um_8.52_i68+ 
   1.3g  19864   2.1     98.8  3   3101:16    /var/lib/boinc/projects/climateprediction.net/hadam4_um_8.52_i68+ 
   1.3g  19864   2.1      0.0  2   3502:12    /var/lib/boinc/projects/climateprediction.net/hadam4_um_8.52_i68+ 
   1.3g  19748   2.1     99.4  1   3112:12    /var/lib/boinc/projects/climateprediction.net/hadam4_um_8.52_i68+ 

The one running @ 0.0% CPU is suspended to run what BOINC client thinks is a more important task

---

Virtual machines. If you are considering running a Linux virtual machine for CPDN using Windows 10 with Oracle VirtualBox 6.1 and ubuntu 20.04 VM, after four months ...

Memory. 16GB physical memory is the bare minimum. The usable VM memory will max out at circa 11GB, leaving 5GB for the M$ OS and bloatware. The Win10 i7-3770 16GB memory PC example, with ubuntu VM and four CPDN tasks, was unworkable for heavy office application users (excel/word/pdf) - the screens would regularly go blank. Resource Manager reported all physical memory was in use. With three CPDN tasks and 10.5GB VM memory it was just about workable, slightly better with two tasks. QED: more physical memory needed.

With 32 GB of physical memory this Win10 PC now runs VitrtualBox with the ubuntu VM and four CPDN tasks; plus heavy office applications and three of the very rare Windows CPDN tasks. The ubuntu VM config is 4 cpu (4 of 8 threads) and 20GB virtual memory. Resource manager reports 28GB physical memory in use, 55% cpu load for VirtualBox and 45% cpu for everything else.

I recall 3GB memory per CPDN task is required? If you don't do anything else on a 4 cpu (8 threads) PC, 24GB physical memory may be enough for running Win10 and VirtualBox with an ubuntu VM and 4 CPDN tasks. If you have a newer multi-processer PC then more memory will be needed,

Virtual Disc. The ubuntu VM will need about 10GB of virtual disc per virtual cpu. That's a virtual disc size of 40GB to run the VM and four CPDN tasks. Youtube videos with tutorials for creating an ubuntu VM in VirtualBox wildly understate the virtual disc storage that is required for CPDN. Schoolboy disc size mistakes in Linux can be fixed with Gparted. If you're worried about Total Bytes Written (TBW) on your expensive SSD, then a small (128GB) SSD is very cheap option.

Old machines, are they worth the effort? We created an ubuntu VM with CPDN on an older headless PC with Win10 and VirtualBox (Q9650 quad cpu, 8GB memory, 128GB SSD). Yes, CPDN worked with two tasks, but there's insufficient memory to run more than 2 tasks on a 4-cpu machine. Not much else would run happily either. QED: Don't bother.

12 Jan 2022.Windows update regularly crashes the VM and tasks. To prevent these crashes: Pause updates in Windows Update, advanced options. You get about one month grace from Windows unexepectedly rebooting.

---

Windows Up-Date killed just the last two hadam4h on this computer https://www.cpdn.org/results.php?hostid=1517859. Approx. 8 days before finishing it. Sorry for that!

---