C++ Threading maximal CPU for a thread

Question

I am using std::threads and in my setup my other threads (variable amount, currently set to 10) are using so much capacity that my used cpu in task manager goes up to 100% for the application. That makes my main thread laggy, which should be real time (I assume that this is the reason for the lag).

I debugged with Intel Amplifier, but there was no other clue why the main thread should lag. My secondary threads where all really busy.

Is it possible to tell a thread how much CPU it can use maximal? How can I make sure that my other threads don't affect the performance of my main thread?

Thread initialisation:

for (int i = 0; i < numberOfThreads; i++)
{
   std::thread* thread = new std::thread(&MyClass::mWorker, this);
   mThreads.push_back(thread);
}

My System: i5-4590 3.3GHz, 8 GB RAM, Windows 8 64 bit, Ogre3D Graphic Engine

You could set the other threads to have lower priority than the main thread: not directly possible in C++11, but you can use the "native" thread id - see [here](http://stackoverflow.com/questions/18884510/portable-way-of-setting-stdthread-priority-in-c11) for discussion/details. — Tony Delroy, Aug 27 '15 at 10:42
I agree with Tony D. You may also consider to sleep your lower priority threads conditionally. — gpicchiarelli, Aug 27 '15 at 10:46
You could also look for improvements in your current design and implementation. — UmNyobe, Aug 27 '15 at 10:46
Thanks! Thread priority gave me a boost for 50 FPS! @TonyD, Make it an answer and you get the credits ! — Anthea, Aug 27 '15 at 10:50
Can accept Rudolfs' answer - was almost the same time as mine, much the same info (and more - affinity's a good alternative to list), and it's the proper thing to do - post an answer not a comment.... — Tony Delroy, Aug 27 '15 at 13:01
I would also notice that 10 threads on 4 cores is a high number. You are talking 2.5 to 1 ratio of threads to core. You might benefit fron lesser number of threads. — SergeyA, Aug 27 '15 at 13:05

score 8 · Accepted Answer · answered Aug 27 '15 at 10:42

I don't think there are any C++11 means for doing that, but you can use platform thread scheduling features with the native_handle that you can obtain from an std::thread and then either set the priority of the threads (e.g. - prioritize the main thread) or set thread affinity so that the main thread is bound to an exclusive core that is not used by any of the worker threads.

C++ Threading maximal CPU for a thread

1 Answers1