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Is this a feature or limitation compared to ordinary single user Windows 7/8? Is there a way to give one user access to say 50, 75% of overall cpu resources for running a software/process?

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3 Answers 3

This very much depends on the process and your processor.

Let's say you have a Quad-Core processor. Windows will represent each core as 25% of the overall capacity of the processor bar it shows in task manager, so a process that is 25% busy all the time may be using 100% of one core and if task manager shows the processor graph at 100% then it's fully using all four cores of our example system. With me so far?

Next under the microsope is the software you're using. Some software is written to perform well in a multi-core environment, some software is less well optimised, and some software will not take advantage of multiple cores at all(*). If your process is pretty much nailed on at 25% all the time, this suggests that it's not multi-processor/core aware (or multi-threaded, if we want to get fancy about it and start giving things their proper name) but it is using the maximum resources that it can see.

If that's the case then all you can do is ask the people who made the software you're looking at what the state of it's support is for multiple processor cores, or look for a hardware platform that runs each core at a faster speed.

(*) Some software won't derive much advantage from multi-core support so this isn't always a bad thing, and even this will be improved on a multi-core system because it can effectively have a core to itself while the system uses the other resources.

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Intel Xeon System we use with 16 cpu cores in the task manager. If we start a cpu heavy numerical simulation, the process never goes over 25%, the software can start also a second or third parallel TCL-based simulation, also only 25% per .exe process for this user. If the software runs on a dual core Windows 7 system than 100% are used. Is there a way to find out if it supports only 2,4,8,16 cores? I didn't see anything mentioned in the software manual about this. –  James Last Mar 9 '13 at 20:04
@JamesLast So have you tested other 'known good' multi-core software to see if this is limited to the app or an issue with the OS or box? Could the app have licence issues where they restrict how it runs in certain circumstances? –  RobM Mar 9 '13 at 21:35
its open source, no license issues. Can you recommend a easy tool to test if settings of windows server restrict the access, just to see how many cores can be used. Is there a easy small to install multi-core software tool to check this, google chrome is multi-threaded, is there a way to make heavy cpu processes inside chrome? –  James Last Mar 9 '13 at 23:04

Yes, there is such way. Please, consult this link (http://technet.microsoft.com/en-us/library/ff384148%28v=ws.10%29.aspx) to adjust maximum CPU usage for a specific user. Now you can have limitations of 25 or less percent causing low usage.

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Sorry but the link you point to discusses how to apply a limit. The OP wants to remove a limit. –  RobM Mar 9 '13 at 19:41
exactly what @RobM said, parallel user are fine, but if only 10% of overall resources are used by the other users, this one should be able to use the 90% free, currently he can use only 25% –  James Last Mar 9 '13 at 19:46
Thanks, I got. I thought you could already installed limitations. Then I fully agree with @RobM answer. –  Meriadoc Brandybuck Mar 9 '13 at 19:48
How many cores do you have? To exclude the influence of unoptimized software you can try launching some program which is fully parallel (for example, the program counting some integral using MPI or OpenMP) and look whether it will also have low performance. If it uses desirable 90 percent, the problem is in your software. Else you'll have to look further. –  Meriadoc Brandybuck Mar 9 '13 at 19:54
Intel Xeon 16 Cores, one process of this simulation software is able to use at least 4 cores, if this the limited by the simulation software or Windows Server is the question. Is there a easy software I can install to test how much CPU a singler user process can take on this Windows server system? –  James Last Mar 9 '13 at 20:08

If you have verified that the CPU Rate Limits setting does not exist for the account running the process, I would suspect a limit in the application.

And yes, it is possible for a single process to use all available processor % and cores.

It's fairly easy for a developer to specify maximum concurrency/threads used by an application. If it is only four threads, the behavior you are observing would be expected. It is not the most sophisticated form to specify a hard-coded value for the number of threads, unless it is some sort of licensing scheme. Some developers would perform a dynamic calculation based on the number of available processors, and perhaps take processor affinity into consideration.

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the software is open-source, are there multi-threading supporting programs that support only 2, 4, 8, ... cores at maximum? So maybe here its 4. Is this technet.microsoft.com/en-us/library/ff384148%28v=ws.10%29.aspx the "procedure" to check CPU rate limits? Is there no interface in Windows server to manage this without hacking around in the registry? What a mess :) –  James Last Mar 9 '13 at 22:53
@JamesLast the thing is of course is that an account shouldn't be rate limited by default. It is a mess but unless you or someone else who administers the box turned rate limiting on for that account then its unlikely to be turned on. If you're confident that its not being applied by GPO or login script then, as rate limiting is a per user setting, there's an obvious test for it here - try a different user. –  RobM Mar 9 '13 at 23:02
@James: what open source application? –  Greg Askew Mar 10 '13 at 0:24

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