# Choose thread **URL:** \ **Category:** GNU Radio\ **Created:** [May 22, 2015, 7:23pm UTC](https://www.ruby-forum.com/t/choose-thread/242050 "2015-05-22T19:23:29Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [May 22, 2015, 7:23pm UTC](https://www.ruby-forum.com/t/choose-thread/242050/1 "2015-05-22T19:23:29Z")
Hi, I’ve a question about thread management…I like the fact that scheduler can launch blocks in different threads, but I’d like to execute some blocks inside the same thread(CUDA require to perform all operations from a single thread)…for the moment I’m using GR\_SCHEDULED=STS,but it blocks at all multithreading…Is it possible to set a thread affinity?(I’ve looked [https://gnuradio.org/doc/doxygen/page\_affinity.html](https://gnuradio.org/doc/doxygen/page_affinity.html), but it doesn’t help) Thanks, marco ---
**Author:** ![marco\_Ribero](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@marco\_Ribero](https://www.ruby-forum.com/u/marco_Ribero)\ **Post date:** [May 24, 2015, 7:53pm UTC](https://www.ruby-forum.com/t/choose-thread/242050/2 "2015-05-24T19:53:15Z")
On Fri, May 22, 2015 at 1:22 PM, marco Ribero [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Don’t use the STS scheduler. It is, after all, the Single-Threaded Scheduler. And setting the thread affinity under that condition is a nop. That will only work with the default TPB scheduler. Tom ---
**Author:** ![marco\_Ribero](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@marco\_Ribero](https://www.ruby-forum.com/u/marco_Ribero)\ **Post date:** [May 27, 2015, 3:31pm UTC](https://www.ruby-forum.com/t/choose-thread/242050/3 "2015-05-27T15:31:19Z")
Il giorno dom 24 mag 2015 alle ore 19:52 Tom R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ha scritto: > Don’t use the STS scheduler. It is, after all, the Single-Threaded > Scheduler. And setting the thread affinity under that condition is a nop. > That will only work with the default TPB scheduler. > > Tom > > I need that different blocks run under the same thread(because CUDA > require to make everything inside a single thread..each thread is > associated to a different GPGPU)..so,without the usage of STS > scheduler,is > not possible to run different blocks with same thread? I’d like that other blocks(not related with CUDA) can run in parallel threads.. Thanks, marco ---
**Author:** ![marco\_Ribero](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@marco\_Ribero](https://www.ruby-forum.com/u/marco_Ribero)\ **Post date:** [May 27, 2015, 4:30pm UTC](https://www.ruby-forum.com/t/choose-thread/242050/4 "2015-05-27T16:30:57Z")
Dear Marco, > I need that different blocks run under the same thread(because CUDA > require to make everything inside a single thread..each thread is > associated to a different GPGPU)..so,without the usage of STS > scheduler,is not possible to run different blocks with same thread? > Yes. The Thread-per-Block-scheduler gets its name from the fact that > every block gets its own thread. > You should really use it – using STS will probably kill the performance > you can gain by accelerating stuff on a GPU, because nearly no one uses > single-core CPUs any more, and to my knowledge, only the FFT blocks are > internally multithreaded. > I’m a bit surprised that CUDA requires you to run everything in one > thread – doesn’t using cudaSetDevice in every thread (==in every > block’s work() method on the first call) suffice? > NVidia claims CUDA is thread safe, i.e. worst case your multi-threading > performance is as bad as doing everything in a single thread. > > I’d like that other blocks(not related with CUDA) can run in parallel > threads.. > That’s really awesome because it scales so well 🙂 Best regards, Marcus ---
**Author:** ![marco\_Ribero](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@marco\_Ribero](https://www.ruby-forum.com/u/marco_Ribero)\ **Post date:** [May 27, 2015, 7:27pm UTC](https://www.ruby-forum.com/t/choose-thread/242050/5 "2015-05-27T19:27:27Z")
Il giorno mer 27 mag 2015 alle ore 16:29 Marcus Müller \< [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> ha scritto: > Yes. The Thread-per-Block-scheduler gets its name from the fact that > every block gets its own thread. > You should really use it – using STS will probably kill the performance > you can gain by accelerating stuff on a GPU, because nearly no one uses > single-core CPUs any more, and to my knowledge, only the FFT blocks are > internally multithreaded. I hope to bring on CUDA the more time-consuming blocks..for the moment FIR and IIR filter, and FFT.. > Best regards, > Marcus It’s my fault: I’ve reason, from CUDA 4.0 the same GPU can be shared between different threads/processes..I got formation from older books 🙂 Thank you!! Now I need to change a litte my code..I was not so concerned about this capability because my blocks just launch asynchronously kernels/memcpy and exit.. It seems that with multithread I’m able to reduce “pause time” between execution of kernels of differents blocks from 1-3microseconds to 0.3microseconds..not bad!!(each block waits the previous with streams attached to events). The drawback is that each kernel execution must be bigger,because otherwise its execution wouldn’t hide the bigger overhead due to “reasignment of device” to a different thread. Thanks for your replies, marco