# Source code annotation using NVTX in CUDA.jl

**URL:** <https://discourse.julialang.org/t/source-code-annotation-using-nvtx-in-cuda-jl/118730>\
**Category:** GPU\
**Tags:** cuda\
**Created:** [August 28, 2024, 6:08pm UTC](https://discourse.julialang.org/t/source-code-annotation-using-nvtx-in-cuda-jl/118730 "2024-08-28T18:08:19Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Cibin\_Joseph](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cibin_joseph/32/208886_2.png) [@Cibin\_Joseph](https://discourse.julialang.org/u/Cibin_Joseph)\
**Post date:** [August 28, 2024, 6:08pm UTC](https://discourse.julialang.org/t/source-code-annotation-using-nvtx-in-cuda-jl/118730/1 "2024-08-28T18:08:19Z")

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I’ve been able to get source code annotation working with the CUDA.jl source code but not with my own kernels.

For example, the following MWE does not seem to work and complains with `unsupported call to unknown function`.

```julia
using CUDA                   
import NVTX                  
                             
function kernel!(a)           
    tid = threadIdx().x      
    NVTX.@mark "here"        
    a[tid] = 1.0             
    return                   
end                          
                             
function main()              
    n = 512      
    a = CUDA.rand(n)         
                             
    @cuda threads=n kernel!(a)
    return                   
end                          
                             
main()                       
CUDA.@profile main()         

```

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<div class="post-metadata">

**Author:** ![maleadt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/maleadt/32/10097_2.png) [@maleadt](https://discourse.julialang.org/u/maleadt)\
**Post date:** [August 28, 2024, 7:01pm UTC](https://discourse.julialang.org/t/source-code-annotation-using-nvtx-in-cuda-jl/118730/2 "2024-08-28T19:01:17Z")

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NVTX is a CPU library, you cannot use it in kernels.

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<div class="post-metadata">

**Author:** ![Cibin\_Joseph](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cibin_joseph/32/208886_2.png) [@Cibin\_Joseph](https://discourse.julialang.org/u/Cibin_Joseph)\
**Post date:** [August 28, 2024, 7:07pm UTC](https://discourse.julialang.org/t/source-code-annotation-using-nvtx-in-cuda-jl/118730/3 "2024-08-28T19:07:50Z")

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Ah! I knew it was something silly! Thanks!