Windows 10 System and Compressed Memory usage

[Calum]

I haven't been able to find much on this from a few Google searched, mostly people complaining that they're seeing this process using lots of CPU or disk.  I'm aware of what it does and why it's useful, but what I'm curious about is why suddenly this process on my system is using almost 10GB of RAM?  Previously, it would be barely noticeable, around 200MB at most.

Now, I'm not complaining because I'm sure it's doing something useful (and one of the things I have wondered about Windows 10 is quite simply why it doesn't utilise more of my RAM), but has anyone else noticed a recent change in behaviour?  I've only noticed this today when I opened task manager for something else, but because I've been mostly using task manager to keep an eye on another program's memory usage I can say fairly confidently that this has started within the last week or less - it may even be since the April updates which were installed this week.

Would be interesting to know how much RAM others are seeing this process consuming, and whether this has changed recently.

[BC_Programmer]

On my AMD build (4GB RAM Total) it is sitting at around 50MB.

On my old build (8GB), which I just powered on for this purpose (the AMD system was asleep), I don't even see a "System and compressed memory" Item. I'm not sure if it might not show up for a while; however this system is running on the "fast" insider track and is using a more recent build than the AMD system. From what I've found it seems to be triggered by a "MemoryDiagnostic" Task in task scheduler. With a little digging I found that the task handler itself is implemented in "MemoryDiagnostic.dll". I started one of the tasks and now the System process has been using one of the cores at 100% for about 10 minutes, so it certainly interacts with the System process. My understanding of how this works is that the scheduled task "kicks off" the construction of the compression store, which as you've likely discovered lives in the System Process. as a result, it also changes the title of the system process to "System and Compressed Memory".

This does increase Memory usage of the system process, of course- but this doesn't mean that added memory usage can always be blamed on the compressed pages.

I did notice there were two tasks, one that seemed to "diagnose" Process memory, and one that dealt with the system memory as a whole. The full diagnostic one doesn't have any triggers defined (or maybe it's a custom trigger) so it's unclear when it runs, but maybe RAM usage spiked because the trigger finally hit.

Another consideration is that it's nothing like SuperFetch- it compresses data that would have otherwise been paged to disk, which means that you'd need many applications open to the point where you'd start seeing swapping before it would start "paging" data by compressing it in a separate area of memory. So maybe you've not typically had enough applications open for that to happen, or when you have, you've not been watching Task Manager quite so closely (since presumably with that many programs open you've got more important things to do).

Isn't that a great thing about Windows? It's no fun working with computers when you actually have usable documentation, after all. /s

[Calum]

Interesting stuff BC, thankyou!

Another consideration is that it's nothing like SuperFetch- it compresses data that would have otherwise been paged to disk, which means that you'd need many applications open to the point where you'd start seeing swapping before it would start "paging" data by compressing it in a separate area of memory. So maybe you've not typically had enough applications open for that to happen, or when you have, you've not been watching Task Manager quite so closely (since presumably with that many programs open you've got more important things to do).

Isn't that a great thing about Windows? It's no fun working with computers when you actually have usable documentation, after all. /s

That's what I don't quite understand - at various times whilst having task manager open I've had a few VMs open allocating 4GB of RAM to each, I've had Firefox eating 2GB of RAM, and I've played various games, at no point have I seen this spike in compressed memory usage, until earlier today.  I saw it had dropped to around 6GB earlier, just checked again now and it's way back down at more usual levels, currently 370MB.
It's not like I was running short on RAM, I mean right now I've got 28 threads of a BOINC project running which are using between 3-800MB of RAM each, Firefox is using 1GB, plus everything else, and I'm at 21GB used out of 32GB...higher total usage than earlier, when 10GB was being used by this system process but my total usage was 16GB, so surely now would be when I'd expect to see more compressed memory, not less?

I don't know, my experiences don't seem to match up with a lot of what I've been reading, and I only have this system running Windows 10 available to me so nothing else to test on unless I spin up some VMs.

As I said, I'm not worried about this as such, just curious to find out what triggered this earlier.  I'll probably try and keep a closer eye on it and see if I can make it happen again, perhaps I'll get some logging set up and see what I can find out.

[Calum]

Huh, and this morning after playing a game, it's at nearly 14GB of compressed memory.
18.5GB "in use", 12.9GB "standby" and 1.1GB "not in use".