Windows 10 task manager is super slow

I'm running a fairly high end computer at around 30% load. For some reason, task manager is very slow. I'm getting black artifacts, the tabs aren't always loading and sometimes it just freezes. Everything else seems to work just fine. For some reason, it's running with normal priority, rather than above normal, and I cannot change it. Maybe this changed with Windows 10?

What can I do about this, other than reinstalling Windows? Is it enough to suspect something messing with task manager, like a rootkit trying to stay hidden?

EDIT: apparently I have a few thousand cmd and conhost running with no parent process. Smallest processid is 224, which is before login. There are also 470k handles open. This will require some digging.

Solution 1:

The huge number of processes was caused by Crashplan crashing due to running out of memory. It tried to restart itself once a minute, but it immediately crashed again, spawning new copies of these processes after each restart.

The memory was capped by the java process at 1GB, but I needed about 3GB of heap. For some reason, they seem to store the entire index of all backed up files in memory. The hotfix was to allow it to use 4gigs of memory; java mx 4096.

The slowness/artifacts of the task manager was probably because I was running thousands of processes; apparently they didn't test that use-case. I guess that they're redrawing the screen based on a wall-clock timer, and that didn't finish drawing the screen before having to start drawing the next one.