I tried this on openSUSE, but I think it has this issues on all Linux distros... but I could be wrong.
For what it's worth, I've seen similar symptoms a couple of times on my test boxes. In my case, there was heavy IO utilization on a relatively slow storage medium and Steam was not the only thing thrashing the hard drive.
I've been seeing this issue every time I start up steam when it is updating all my games and on every shutdown, it also doesn't just slow down/freeze steam it causes slowdowns in KDE Plasma 5 for me.
Most of the Steam install is on a hyper fast NVMe drive so I/O shouldn't be an issue, I do have an additional steamapps on a magnetic drive, but that one isn't exactly super slow either.
While I don't think Steam should be able to generate enough I/O to slow down my system if it behaved correctly I do still agree that it might be I/O causing the slowdowns since I'm seeing spikes in my Proc graph which usually indicated I/O heavy tasks.
It is also worth mentioning that Steam never caused those slowdowns half a year ago on the same system and I'm seeing them both on my desktop and my laptop, both of them have Steam installed onto NVMe. I also have completely reinstalled this machine since this issue started and it manifested in exactly the same way on the fresh install. So I have a feeling Steam is misbehaving in some way and blasting some I/O heavy syscalls in a loop at high frequency where it would be perfectly fine to make the same syscall much less frequently.
You need to lower your dirty ratio cache settings. Modern machines with large amounts of ram have these default (percentage) values set way too high.
For example, lower values:
sysctl -w vm.dirty_background_bytes=64000000
sysctl -w vm.dirty_bytes=512000000
Will solve the lockup problem. Add these to the appropriate config files to make permanent.
Nothing extracted yet.
Your system information
Please describe your issue in as much detail as possible:
Describe what you downloads work with buttery smooth steam client and what did happen. Client stops responding at times for up to 30 seconds or longer. Maybe you need to set the -niceness for backgrounds downloads, extractions...
Steps for reproducing this issue: