I wasn't going to reply to this, but...
Firstly, please reply to Asyn's request - all valuable (and important) info.
Now my 2 cents:
Aswidsagenta.exe is the Avast Behaviour Shield process. Your Task Manager screenshot also shows
thinkorswim.exe using over twice as much memory as aswidsagenta.exe. This suggests a lot of activity and resource use, causing aswidsagenta.exe to have to work harder.
As for
I tend to keep my computer on for days (sometimes even weeks) at a time
it may be time to Read The Fine Manual for M$ operating systems.
NTFS is a journaling file system (
https://en.wikipedia.org/wiki/Journaling_file_system) and
NEEDS to be rebooted regularly (at least weekly - ideally daily, IMHO). Why...?
caches fill up
page swapping occurs more regularly
databases used by Windoze (there are hundreds of them) need to be consolidated or compacted
background updates (to the OS or user-installed software) need to update files that are in use by the OS
the Journal needs to be flushed to disk and its memory reclaimed
etc., etc.
At a minimum in this case, please reboot (NOT restart or just logout) and re-evaluate the memory usage. By all means report back
Rant over! But the advice to reboot is not just an IT Guy's get-out: it will keep your OS (and its resource use) in better shape, as well as improving interaction between processes running on the machine.