StringBuilders magic for very large strings

[giscus[bot]]

StringBuilders magic for very large strings

The StringBuilder class is used to create mutable sequences of characters. Strings are immutable, so if you need to perform multiple operations on a string, it is better to use a StringBuilder instead of a string. This is especially useful when you need to concatenate a large number of strings. But there is more magic to it, especially when we go BIG!

https://steven-giesel.com/blogPost/c0144fea-0ff8-4638-be01-b62b48ef7188

[Patrick-3000]

Very nicely explained! So just that I get it right: the internal implementation of the StringBuilder class is responsible for the fact that StringBuilder instances dont live on the LOH, and this is a good thing because they can now be compacted on the "normal" heap?
What I think I missed: where does the big difference (factor of 2) in memory allocation between StringBuilder() and List() come from?

[linkdotnet]

Basically, yes. The implementation detail that there is no single object that can grow bigger than 85'000 bytes is the reason that StringBuilder doesn't end up on the LOH.

The Large Object Heap can also be compacted, but you have to specifically ask for that:

// Don't just "do" that. That is something you want to benchmark for your scenario
// Game-Engines are potentially benefiting from this
GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce;
GC.Collect();

Regarding the Memory of List and StringBuilder I did update the original blog post (see the last section). I hope that answers your question. If not let me know.

Grüsse
Steven

[Patrick-3000]

Now it is clear for me, thank you very much!