# Profiling in VSCode returns some red bars with "Flag: GC" - what do they mean?

**URL:** <https://discourse.julialang.org/t/profiling-in-vscode-returns-some-red-bars-with-flag-gc-what-do-they-mean/109570>\
**Category:** General Usage\
**Created:** [February 1, 2024, 1:07pm UTC](https://discourse.julialang.org/t/profiling-in-vscode-returns-some-red-bars-with-flag-gc-what-do-they-mean/109570 "2024-02-01T13:07:05Z")\
**Posts on this page:** 1\
**Showing post:** 12

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**Author:** ![mstewart](https://avatars.discourse-cdn.com/v4/letter/m/b5a626/32.png) [@mstewart](https://discourse.julialang.org/u/mstewart)\
**Post date:** [February 6, 2024, 2:02pm UTC](https://discourse.julialang.org/t/profiling-in-vscode-returns-some-red-bars-with-flag-gc-what-do-they-mean/109570/12 "2024-02-06T14:02:26Z")

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I tried out your `updatexᵢⱼ!` function on some made up vectors. With `@code_warntype` and using Julia 1.10.0, I see the yellow under locals at `@_5` but not at `%6`. Maybe that is some difference across versions in how `@code_warntype` presents the same information? In any event, I think that `Union` is just the result of iteration returning `nothing` at the end of the iteration: [@code\_warntype gives yellow ::Union{Nothing, Tuple{Int64,Int64}} in for loops](https://discourse.julialang.org/t/code-warntype-gives-yellow-union-nothing-tuple-int64-int64-in-for-loops/52814). The yellow on the line that calls `updatexᵢⱼ!` in your image of the code looks like some information provided by VS Code, which I am not using, so I don’t know how that works. I’m not an expert at tracking down allocations, but it all looks harmless to me, and it definitely doesn’t seem to be allocating on my system.

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