# Does the interactive thread have due performance?

**URL:** <https://discourse.julialang.org/t/does-the-interactive-thread-have-due-performance/137568>\
**Category:** Performance\
**Tags:** multithreading\
**Created:** [June 11, 2026, 1:58pm UTC](https://discourse.julialang.org/t/does-the-interactive-thread-have-due-performance/137568 "2026-06-11T13:58:33Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![WalterMadelim](https://avatars.discourse-cdn.com/v4/letter/w/3e96dc/32.png) [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Post date:** [June 11, 2026, 1:58pm UTC](https://discourse.julialang.org/t/does-the-interactive-thread-have-due-performance/137568/1 "2026-06-11T13:58:33Z")

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I have 2 physical chips on my machine, each having 64 physical cores. So there are 2 \* 2 \* 64 = 256 virtual processors.

```julia-auto
julia> Sys.cpu_summary()
AMD EPYC 7763 64-Core Processor: 
           speed user nice sys idle irq
#1-256 1550 MHz 66788279 s 511 s 944202 s 1757367696 s 0 s 

```

Now I start julia with `julia --threads=255,1`.

I need to run cpu-heavy tasks in all the 255 threads within the default pool (spawning them at the background). But I also expect full performance in that single thread in the interactive pool (I also need to run a cpu-heavy work on the foreground, i.e. where the interactive thread goes).

I wonder if under this setting I can get expected performance on the single interactive thread? If not, how should I remedy? Will starting with `julia --threads=254,2` be a fix?

Thanks.

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**Author:** ![Benny](https://avatars.discourse-cdn.com/v4/letter/b/49beb7/32.png) [@Benny](https://discourse.julialang.org/u/Benny)\
**Post date:** [June 11, 2026, 3:54pm UTC](https://discourse.julialang.org/t/does-the-interactive-thread-have-due-performance/137568/2 "2026-06-11T15:54:51Z")

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Interactive threads aren’t different, just in a separate threadpool from the default threadpool where `@spawn` schedules the typical thread-hogging CPU-bound tasks. If you need interactive or very responsive tasks like the REPL, dynamic plots, or server loops, specifically spawn them on a few interactive threads. If you don’t need them at the moment, you can spawn some CPU-bound tasks on the free interactive threads. If your process doesn’t need interactive or responsive tasks at all, run a `julia --threads 256,0` process, allowing all threads in one pool to freely trade tasks.