High CPU usage - slow/lag/skip problem

[Christopher Barry]

On Wed, 10 Aug 2016 19:16:57 -0400
Zurd <zurd33 at gmail.com> wrote:

>Hi, me again, I'm bumping this. I realized I have a big post but I
>wanted to put as much information as possible. All I want to know is
>how to minimize the xrandr calls so that there's less EDID information
>in Xorg.0.log.
>
>My system is not slow yet but it should happen soon. My Xorg log is at
>23M in just 6h12m. I don't think this is normal.
>
>
>On Sun, Aug 7, 2016 at 10:54 PM, Zurd <zurd33 at gmail.com> wrote:
>
>> Hi all! I have a problem where Xorg is taking around 30% CPU usage
>> and it create a slow/lag problem for a fraction of a second about
>> every second. There's no crash but it's quite annoying. Sometimes a
>> click is not registered.
>>
>> It can happen 5 minutes after I boot or after 5 hours. I haven't
>> been able to know why, it's random. It looks like the same problem
>> as this:
>> https://lists.freedesktop.org/archives/xorg/2011-September/053299.html
>>
>> He sums it up quite well by saying:
>> "I can notice the lag in response time. Video playback also becomes
>> impossibly slow at this point."
>>
>> I started a thread on the linux mint forums with a lot of my hardware
>> information:
>> https://forums.linuxmint.com/viewtopic.php?f=47&t=226421
>>
>> Problem started with a new clean install of Linux Mint 18 and I
>> haven't been able to solve it. So I went back with Linux Mint 17.2
>> that I had before and that there was no issue but now the problem is
>> also there. I now have a good theory on why I have a high cpu usage
>> of Xorg and it's because of my ultra widescreen monitor. When I
>> installed Linux Mint 17.2, I had a regular widescreen monitor and
>> Xorg was configured with it. Then I switched to my new ultra
>> widescreen and everything was well. Until I decided to completely
>> format and install the new Linux Mint 18.
>>
>> My monitor is an LG 29UM58-P, resolution is 2560x1080.
>>
>> So now I'm wondering if the problem is about EDID:
>> https://wiki.ubuntu.com/X/Troubleshooting/HighCPU
>> "An example we saw is where a daemon process does polling on X
>> calls, such as to watch for if a monitor is present. These xrandr
>> calls can be expensive because they do a probe and analysis of the
>> monitor's firmware. So as a result the daemon drives X's CPU
>> utilization through the roof (and causes a bunch of EDID stuff to
>> fill up the Xorg.0.log). The solution in these cases is to make the
>> daemon stop doing the expensive polling so frequently (there are
>> cheaper X calls they can use)."
>>
>> This whole paragraph on EDID/polling/xrandr is quite interesting but
>> there's no information on how to troubleshoot or solve that problem
>> which is why I'm posting here. Anyone can shed some lights?

Based on the above, could it be possible that a utility daemon, e.g.
something that's part of the distro itself (not part of X, per se), is
the culprit here?

Try using ps to see if you can glean some more info.

(or use 'pstree -paul' for a nice view of processes if you have it
installed [pkg: 'psmisc' in Debian derivatives])

both of the above are terminal programs by the way...

>>
>> I have a feeling it's about EDID because in my log file
>> /var/log/Xorg.0.log, I see a bunch of
>> [   434.373] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> connected
>> [   434.373] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> Internal TMDS
>> [   434.373] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> 340.0 MHz maximum pixel clock
>> [   434.373] (--) NVIDIA(GPU-0):
>> [   434.907] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> connected
>> [   434.907] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> Internal TMDS
>> [   434.907] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> 340.0 MHz maximum pixel clock
>> [   434.907] (--) NVIDIA(GPU-0):
>> [   434.940] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> connected
>> [   434.940] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> Internal TMDS
>> [   434.940] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> 340.0 MHz maximum pixel clock
>> [   434.940] (--) NVIDIA(GPU-0):
>> [   435.474] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> connected
>> [   435.474] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> Internal TMDS
>> [   435.474] (--) NVIDIA(GPU-0): LG Electronics LG ULTRAWIDE (DFP-1):
>> 340.0 MHz maximum pixel clock
>> [   435.474] (--) NVIDIA(GPU-0):
>>
>> If you look at the timestamp, it happens very very often and it keeps
>> filling up the log file. After 23 minutes of uptime, the log file
>> Xorg.0.log is already at 1.5M.
>>
>> Note that I'm using the latest nvidia driver and that this problem
>> doesn't happen with nouveau. If I log out and back in again, the
>> problem goes away but will come back.
>>  



--
Regards,
Christopher Barry