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#1 2019-07-24 09:23:27

epinephrine
Member
From: Frankfurt
Registered: 2012-10-18
Posts: 84

[SOLVED][T480] Bad system performance with external monitor(s)

I experience strange performance problems with my Lenovo T480: The more external monitors I connect, the slower and less responsive the whole system becomes, badly. It is not just one application, but everything becomes super slow and laggy.
To counter-check, I started up a Manjaro Live system with the same monitors connected (via USB-C, each) and it doesn't experience this behavior at all. The live system stays snappy. Connecting one monitor via HDMI doesn't make any difference.

Some examples:
- I sit in a Uni with 1Gbit/s networking connection.
   - Directly plugging the networking cable into the onboard card, no external monitors attached, I see 900 Mbit/s down- and upload (checked with speedtest.net).
   - One 4K monitor attached (via USB-C), I already see  a decreased throughput of ~350-400 Mbit/s.
   - Two 4Ks attached, I observe something around 150-200 Mbit/s. The whole system is generally very laggy. CPU usage of firefox goes to 280% in htop. But at the same time the CPU clocks at 3GHz.

- Accessing a self-hosted Gitlab on the local network, everything loads super fast without any monitor attached. With one monitor it already loads slightly slower and with two it takes 30 seconds just to load a merge request page, together with some comments and changes. It is definitely not the Gitlab server as I can confirm from my co-workers browsers. There is also no difference in using Firefox or a clean Brave browser (Chromium engine).

- Also my vim gets very laggy and slow the more monitors I connect. I currently code in Go with a language server running in the background, and autocompletion and live-linting barely works when two monitors are connected. Without them, it works like a charm.

System Setup (following some advice from https://wiki.archlinux.org/index.php/Le … nkPad_T480):
- throttled lenovo_fix.service is running to counter throttling issue.
- The NVIDIA card is completely disabled. the nouveau module is blacklisted and I load bbswitch with options bbswitch load_state=0 unload_state=0. I also disabled bbswitch and let nouveau load, which didn't make a difference.
  - no other module configurations in /etc/{modprobe.d,modules-load.d}
- I use i3 and start it directly form the command line with startx. I don't have any special Xorg configuration.
- I use the vanilla kernel with command line

initrd=\intel-ucode.img initrd=\initramfs-linux.img root=LABEL=root rootflags=subvol=/root,ssd,relatime rw rd.driver.blacklist=nouveau nouveau.modeset=0

I really don't know what is going on and where to look. Any help is greatly appreciated!

Last edited by epinephrine (2019-07-26 18:05:09)

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#2 2019-07-24 10:42:03

kokoko3k
Member
Registered: 2008-11-14
Posts: 1,882

Re: [SOLVED][T480] Bad system performance with external monitor(s)

Long shot...
You could try to disable compositor vsync or maybe remove xorg tearfree option if enabled or swirch from intel to modesettings driver.

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#3 2019-07-24 11:58:31

epinephrine
Member
From: Frankfurt
Registered: 2012-10-18
Posts: 84

Re: [SOLVED][T480] Bad system performance with external monitor(s)

Thanks! But all those things are on by default in the Manjaro Live system no? Why does Manjaro live just work out of the box?
I think it must be something "deeper" wink

- disable compositor vsync: how do I do that?
- xorg tearfree: will try, although that shouldn't have such a crazy performance impact, I think.
- modesettings driver: will try, will also check if that one is actually used in Manjaro Live.

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#4 2019-07-24 13:34:37

kokoko3k
Member
Registered: 2008-11-14
Posts: 1,882

Re: [SOLVED][T480] Bad system performance with external monitor(s)

I've no idea what manjaro uses by default.

disable compositor vsync: it depends on your compositor, if any.
xorg tearfree: neither more monitors should have a performance impact on your network bandwidth; but more monitors means more vblanks to sync on, so i'd try.

Last edited by kokoko3k (2019-07-24 13:36:55)

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#5 2019-07-24 18:37:57

epinephrine
Member
From: Frankfurt
Registered: 2012-10-18
Posts: 84

Re: [SOLVED][T480] Bad system performance with external monitor(s)

It actually was my compositor, compton! I just started it with compton -b and didn't suspect it to horribly slow down the whole system. I work without a compositor now, also works fine. Although I see the missing compositor in apps like vim. I guess I need to figure out a working compton configuration, or do you have any other recommendations?
I also found this related reddit thread.

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#6 2019-07-24 20:34:58

kokoko3k
Member
Registered: 2008-11-14
Posts: 1,882

Re: [SOLVED][T480] Bad system performance with external monitor(s)

"disable compositor's vsync"

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