Setting affinity for third party applications that create threads

[dehvidc1]

Hope this is the correct forum to ask this question.

We can use KMP_AFFINITY and associated infrastructure to set affinity for threads spawned by applications we've developed. And we can use numactl to bind a single-process third-party application to a core. What's available to bind threads spawned by a third-party process to a particular core? We can set what's effectively a CPU set using numactl for a third-party application. The threads spawned by a third-party process will stay within this CPU set but appear to move around between cores. I would be grateful for pointers on how we can bind threads spawned by a third-party process to a particular core

Thanks

David

[Vladimir_P_1234567890]

hello David,

you can use affinity API to pin 3rd party threads to cores:

sched_setaffinity() for linux, cpuset_setaffinity() for FreeBSD or SetThreadGroupAffinity() for windows.

--Vladimir

[TimP]

Do you mean there is a requirement not to link against libgomp or libiomp?  taskset may be of use

[dehvidc1]

Thanks for the replies. My problem is how I can set affinity to cores with third-party applications. These are applications for which I don't have the code so I can't compile and link them.

Is there any way to fix a thread to a core for threads spawned by a third-party application for which the source code is unavailable?

Thanks

David

[James_T_Intel]

From outside of a process, you're really only going to be able to control the affinity of the entire process.  Depending on how the application spawns its threads, you *might* be able to bind the process to the desired core, let the application spawn the thread, and then move the main process.  I don't really expect that to work, but it might be worth exploring if you absolutely have to pin the applications threads to individual cores.

[TimP]

If you're looking for an answer which is independent of which OS, MPI and threading model is used in the application, I think you're out of luck.  Your reference to numactl would seem to indicate linux with pthreads, in which case you could set up a separate taskset selection for each MPI process, giving each process a selection of hardware contexts, with an effect similar to what you would get by setting KMP_AFFINITY for each process when libiomp is in use.

I don't see you explaining why you like numactl for a single-process application but not for multiple processes.  I suppose numactl or taskset may be applicable only for MPI_THREAD_FUNNELED model, but you didn't say explicitly that you have something different in mind.

I guess you may not have meant to ask for an equivalent to KMP_AFFINITY which works for any pthreads application.  Standard equivalents to KMP_AFFINITY are OMP_PROC_BIND and OMP_PLACES, but I'm sure you could find applications built not so long ago against libraries not sufficiently up to date to support them.