Questions on CPU Freq

[digitaltopo]

Hi Frank, thanks for all your docs on the XPS. I have the same model and have being using linux/ubuntu since I got it around Oct 2015.

I recently upgraded to Xubuntu 16.04 and am running Linux mainline kernel 4.8.4-040804-generic. Performance on the laptop doesn't feel as good as it should. Although it rarely crashes, the speed seems pretty bad for the i7 with 16gigs and nvme ssd. I was wondering if you had any tips on optimizing performance that you could share, or some ideas on how I could figure out what the bottlenecks are. Thanks and please get in touch via github or email at designed@digitaltopo.net.

[fszf]

Thank you. Phrases like "pretty bad" are highly subjective. You'll have to describe it in full detail or screen record it. I don't think this issue is device specific as nobody else is concerned with this. Unfortunately I do not use *buntu so I'm not sure what your system defaults are.

Sorry, I don't think I'm the right person to help although I don't mind trying.

There is no optimization that needs to be done. I recently picked up the 9360(kaby lake) i7 16gig and this flies. Some questions to think about:

1. Does this "slow down" happen in all programs? If yes, have you tried a clean install?
2. Have you looked at htop and iotop to see any abnormal process or disk activity?
3. What is autostarted?
4. Pipe out the dmesg and other logs using ix
5. In htop how is the cpu activity?
6. Have you checked the ubuntu forums for similar issues?

[digitaltopo]

Apologies if my questions seemed pretty general, I can try to be more specific about my general setup.

I notice sluggishness when using several chromium browser windows and tabs which seem to eat up a lot of ram. Usually I'm also doing something in an IDE like visual studio code or sublimetext with a few files open, and running node build tools like gulp or grunt or webpack etc in the background. I also use vagrant and virtualbox. I also have a decent sized 4k external monitor plugged in.

In autostart, I have a couple electron based apps like slack, and dropbox, plus the stock xfce apps for the window manager.

For example as I write this, htop reports I'm using 8 of 15.5 gigs of ram and the cpu cores are all hovering between 5% and 15% usage. I currently have about 6 chromium windows open each with 2-5 tabs open. I'm experiencing some occasional mouse stuttering. When I begin working with apps like inkscape or open office, or have a couple instances of the IDE open, I see a lot more sluggishness. When I watch 4k video, the playback stutters every 5-10 seconds, which is unfortunate given the great screen on the laptop.

I've also noticed that when I resume from suspend, the computer generally feels slower. I've seen some posts about the intel_pstate not coming back to the right place, and CPU frequency getting capped at a low level. PowerTop puts the cores at about 600-800 MHz right now (which I think is an average for a snapshot taken at a certain interval) and lscpu |grep MHz reports the following:

CPU MHz:               499.877
CPU max MHz:           3100.0000
CPU min MHz:           400.0000

I guess that's an instantaneous reading, but I haven't seen stay consistently higher when I'd expect it to be.

I just did a fresh install of the system about a week ago, and I'm also up to date with all Dell drivers and bios, and have run the Linux Intel graphics tool to update video drivers. I have the slightly older version of the xps than you, with the skylake processor and the older intel graphics. I've looked through some of your configs and will try out some of your settings to see if there is a difference.

It's not that the computer is always slow or locked down constantly, but I get the feeling that it should be able to handle much more load given the hardware. I also use a macbook pro at work (which is a couple years older and has different hardware, but) and it seems to be able to handle way more load. I also have a Windows installation on the xps that feels a bit smoother. In linux, startup is generally very fast too.

I guess I was wondering if you had any clear debugging methods I could follow to try to pinpoint any bottlenecks and check all my bases, or if you could outline any steps you took on installing to ensure performance, like SSD settings, kernel settings, or power management settings.

I appreciate your help and time, and please let me know what else I can look for. I've attached my dmesg from today and I'm seeing a few issues popping up in there. dmesg.txt

[fszf]

I'm about to go to bed. Configs are from various devices and aren't always updated. Just a snapshot of when I upload. there really is nothing in configs that would resolve this.

I'll add more response tomorrow.

[fszf]

Try the link you posted and adapt it to ubuntu. Also try the other things I've mentioned. Perhaps create a new user and limit the apps running in background. Try to run in a clean environment without adding more variables. Last test would be to do a clean install of ubuntu.

Once again, this doesn't sound like an optimization issue but more of a bug. Our machine should easily handle the load you described. On a clean arch install without any tweaking/optimization, the xps flies for me in similar workloads.

As I am not there on your hardware, you'll just have to ask yourself the question of 'what did you do?'. For example, did you run any power saving daemon that limits your cpu freq when on battery?