Skylake vs Broadwell-E interactive desktop performance

[Fite]

I built two similar systems. One is a Skylake Core i7 6700K system with an Asus Z170A mb and GTX 960 GPU. The other is a Broadwell-E Core i7 6850K with an Asus X99 Deluxe II and GTX 970 GPU. Both use Mushkin SSDs. Both run Linux (KDE). Neither is overclocked.

These are business PCs for spreadsheets, content creation, etc. Not used for any gaming.

The Skylake system performs fine. The Broadwell-E system suffers lag with interactive desktop applications. For example, resizing windows is very laggy. See screenshots here: http://imgur.com/a/6Asvh. Notice how much lag there is between the mouse cursor position and window edge. Also notice the lag of content redrawing.

The Skylake system has little to none of this GUI lag. The Broadwell system also lags in other ways that are obvious in everyday use -- but no lag shows up on any benchmarks that we have run (at least so far).

Bottom line: in actual use, the Skylake system performs well and the Broadwell-E system is annoying due to lag. We can't pinpoint a reason for this.

I have tested a bunch of hardware and software variations. I have installed Ubuntu, opensuse and Arch Linux. I reinstalled Arch 8 times "to be sure." I swapped video cards between systems. I changed out almost every hardware component of the Broadwell system. At this point no component of the Broadwell-E system remains from the original except the monitor, keyboard and mouse. Through all these changes the Broadwell system remains laggy. (And also no specific issue responsible for the lagginess shows up in benchmarks.)

Any ideas? Has anyone else seen anything similar under Linux?

 

[lakedude]

Some time ago my friend had similar trouble with his magny cours and the trouble was that the software was not compiled to use all the available cores. It needed to be recompiled for the specific CPU it was running on.

Also I believe the 6700 is faster at lightly threaded tasks.

Don't know if this will help but you might check into it.

Also one might be using video acceleration and the other may not or it may be buggered. This actually makes the most sense now that I think about it.

Are you sure you are making use of the aftermarket GPUs? Maybe the 6700 is running onboard video and the 6850 is using just the CPU for all the graphics?

 

[PeckingOrder]

why do you need a i7 6850K in a business PC for spreadsheets?

 

[Fite]

Some time ago my friend had similar trouble with his magny cours and the trouble was that the software was not compiled to use all the available cores. It needed to be recompiled for the specific CPU it was running on.

Also I believe the 6700 is faster at lightly threaded tasks.

Don't know if this will help but you might check into it.

Also one might be using video acceleration and the other may not or it may be buggered. This actually makes the most sense now that I think about it.

Are you sure you are making use of the aftermarket GPUs? Maybe the 6700 is running onboard video and the 6850 is using just the CPU for all the graphics?

Thanks for all the ideas.

I did check that the 6850K is using all cores. (But as you suggest, the tasks where I'm seeing the lag are not dependent on multiple cores.)

Both computers are running the proprietary nvidia driver (latest version) and both are running the same driver settings.

The nvidia settings tools indicates that the GPU is in use on both systems.

 

[lakedude]

Hmm, are you using all 4 memory channels in the 2011 system?
If not try using all 4, if not maybe try taking some out just as a test.

 

[lakedude]

Try running a simple 3d browser based benchmark on both systems to make sure your application is making use of your GPU.

Might be a simple checkbox with GPU acceleration turned off for some reason, or maybe network issues since you seem to only be having trouble while on the internet.

 

[Ken g6]

Sounds like drivers to me. I'd suggest you try installing the official (no-charge, but "non-free") Nvidia drivers.

Edit: Installation instructions:

1. Switch to a virtual terminal. (Ctrl-Alt-F2, say. F7 is usually your GUI.)
2. "sudo service stop" your window manager. I'm never sure what that is for any given Linux; you'll have to look it up.
3. sudo run the drivers binary you downloaded. It should be self-explanatory.
4. "sudo service start" your window manager, which should put you back in your GUI automatically.

 

[Burpo]

https://access.redhat.com/documenta...Linux/6/html-single/Performance_Tuning_Guide/

" And as discussed earlier in Section 1.2.2.1, “Parallel Computing”, many mid-range systems nowadays contain more cores than yesterday's high-performance machines.
Many modern applications are designed for parallel processing, using multiple threads or processes to improve performance. However, few applications can make effective use of more than eight threads..

..some resources (such as I/O and network communications) are shared, and do not grow as fast as CPU count. As such, a system housing multiple applications can experience degraded overall performance when one application hogs too much of a single resource.
To address this, Red Hat Enterprise Linux 6 now supports control groups (cgroups). Cgroups allow administrators to allocate resources to specific tasks as needed.
As a result, both database and web applications deliver good performance, as the system prevents both from excessively consuming system resources. In addition, many aspects of cgroups are self-tuning, allowing the system to respond accordingly to changes in workload."