High processor load on i7 (Skylake) with many threads on .net application

[BBirg]

Hi,

We have a problem with the new Skylake processors when running our application.

The application is developed on c# .net platform and is easily using using 600-800 threads when running. We currently use 3770 processors on our machines and it works well.

Looking for an upgrade we started a test with 6700. This has not gone well at all. We see significantly higher CPU load. The strange thing is that if we turn of hyperthreading the CPU load drops significantly. In one test from 85% to about 45%.

Could this be related to the bug referred here: http://www.pcworld.com/article/3021023/hardware/how-to-test-your-pc-for-the-skylake-bug.html How to test your PC for the Skylake bug | PCWorld ?

Or is this by design and hyperthreading is not suitable for this type of load and we need to move away from CPUs with hyperthreading?

Any advice would be highly appreciated

Kind regards / Birger

[idata]

Hello BirgerK,

If you developed your own application, the best place to get more answers in regard to his behavior is Intel® Developer Zone; this is the place to ask questions (and get answers) related to all aspects of programming on Intel® Architecture. See here for the forum support: https://software.intel.com/en-us/forum https://software.intel.com/en-us/forum.

Regards,

Amy.

[BBirg]

Hi Amy,

Thank you for your response, but I don't understand which forum it is that I should use from the list.

And also, I'm not sure this is a coding problem since this only occurs on the 6700 processor.

Kind regards

Birger

[idata]

How good was the performance at that test? Was it less than 3770?

[BBirg]

Hi Tugrul,

The 3770 is massively better than the 6700 so far.

We have a test scenario that was run on both versions.

- Windows 7, same install except for system drivers

- Exactly the same test setup with load generators

- Exactly the same network

- Exactly the same install of our application

The average CPU load over the one hour scenario was around 15% on the 3770 and the 6700 was over 60%.

We have doen some preliminary tests with hyper threading turned off and the CPU load drops significantly. I will not present any numbers here before we have run the complete scenario.

Kind regards

[idata]

Since you mentioned that you developed your own app, Intel® Developer Zone might be the right place to get more feedback.

How are you checking the CPU load? Through Task Manager?

Have you tried testing a different processor model?

Let me know as soon as you have results ready.

Regards,

Amy.

[BBirg]

Hi Amy,

We have tested this load scenario on different architectures.

- with E5-1620 v3 @3.5GHz (For standard server rooms)

- with i7 4700MQ 2.40GHz (Used on din rail mounted embedded industrial server)

- with i7-6700 3.40 GHz (Our candidate for next gen +55 degree environments)

- with i7-3770 3.40 Ghz (Our old platform for +50 degrees environments)

All currently only tested for this scenario in standard server room temps.

I'll check with the engineer who did the measurement to see how it was performed.

Kind regards / Birger

[BBirg]

Hi,

Regarding the measurements:

We are using the following performance counters from Windows Performance Monitor:

Processor\% Processor Time

Processor\% User Time

Processor\% Interrupt Time

System\Processor Queue Length

Kind regards / Birger

[idata]

So, this is narrowed to the http://ark.intel.com/products/88196/Intel-Core-i7-6700-Processor-8M-Cache-up-to-4_00-GHz Intel® Core™ i7-6700 Processor (8M Cache, up to 4.00 GHz) Specifications. Have you tried testing a different unit of the same model?

Regards,

Amy.

[BBirg]

Yes.

We have now done a test on anohter 6700 machine. It's on a different motherboard than the new server sample. The load is also much higher on this than the original 3770.

We have a second server sample out at a customer site for testing that we will rerun the tests on when it's returned. Hopefully soon.

There is also planned a rerun of the test scenario with HT turned off. I'm not sure when we can fit this test in though.

Kind regards / Birger

[idata]

Keep me posted, were are really interested in your outcome. All information you can provide will help to address this issue, from our end we will need you to test all possible scenarios, motherboards, servers, processors, etc. And, this is based on fact you customized your app, so it's going be difficult to replicate this in our systems.

Regards,

Amy.

[BBirg]

Hi,

Would you be able to replicate in your lab if we send over test lab setup and applications used?

I'd rather not publish all details on this open forum, but we can send over details on motherboiards, bios versions, OS and patch level ++ to you if that's possible.

Kind regards / Birger

[idata]

Yes, I can give it a try, Like you mentioned we would need the app and all the documentation with the steps of how to replicate.

You could try something like this https://www.youtube.com/watch?v=6jNSaSoOM0s How To Password Protect ANY File in Google Drive - YouTube, and then just send the password to me.

The content on the above site is not controlled by Intel. This information is offered for your convenience and should not be viewed as an endorsement by Intel for the merchants or services offered there.

Regards,

Amy.

[idata]

/thread/108389 BirgerK,

I am following up your thread, and waiting for your answer.

Please let us know if you need further assistance.

Regards,

Amy.

[BBirg]

Thank you for following up Amy.

I have had to assign the test facility for some release related activities for some days. We have scheduled a test with the Skylake 6700k after this test is complete. Probably early next week.

How can I securely send you link and password for download of material? I don't see a way to send you a direct message that is not public on the forum.

This will be from my company's secure download service.

Kind regards / Birger

[Amy_C_Intel]

Use this profile for the password; Amy_Intel

Regards,

Amy.

[idata]

Please let me know as soon as you send the information to my profile.

Regards,

Amy.

[CHope1]

Here is a summary of the measured load,

All tests are done using the same load type, software versions and test equipment, the only difference is the machine under test.As seen by the numbers in the image/table below

• The current gen. server has a load of 14% while running on Win7 and 18% on Win 10. Turning off hyper threading lowers the performance
• All machines running on the Skylake CPU has much higher load 63% and 43% even if they should be more powerful CPUs.
• The E5-1620 v3 should also have been a more powerful CPU, but it also is outperformed by the older less powerful 3770 CPU.
• The i74700MQ has as expected a bit higher load than the 3770.

Kind reagrds,

Carl

[idata]

CarlH thank you for your input. Just to confirm; is this related to the same issue that BirgerK reported?

Regards,

Amy.

[CHope1]

Yes, this is related to what he reported.

[idata]

Thank you for your input, let's hope it can help /message/443632?tstart=0 BirgerK.

Regards,

Amy.