Post History

Can I set a memory limit for the .NET Core garbage collector to collect objects more aggressively?

Can I set a memory limit for the .NET Core garbage collector to collect objects more aggressively?

I have an ASP.NET Core 5 web application that provides functionality that involves file upload + rather large processing (memory consumption mainly). After each processing (with success or not) the memory could be reclaimed.

I have a stress test the endpoint with large files and checked the w3wp.exe process Memory (it runs in IIS) which goes something like this:

- step 1: 400M
- step 2: 800M
- step 3: 1200M
- step 4: 1800M
- step 5: 1300M

So there seems to be no memory leak, but GC kicks in very late. I would like for it to begin the cleanup faster, but I cannot seem to find a way to do this. What I have found/tried:

- **why the delay in collection?** - objects larger than 85KB are considered [large by the GC] (https://docs.microsoft.com/en-us/dotnet/standard/garbage-collection/large-object-heap) and will be collected less frequent than smaller objects
- **forcing the GC collection after each operation** - this can be done using `GC.Collect()`, but it is [not recommended to do so](https://stackoverflow.com/questions/118633/whats-so-wrong-about-using-gc-collect) 
- **Runtime configuration options for garbage collection** - I have checked [GC settings](https://docs.microsoft.com/en-us/dotnet/core/run-time-config/garbage-collector) and applied a limit for `System.GC.HeapHardLimit`, the final configuration looking like this:

```
{
  "runtimeOptions": {
    "tfm": "net5.0",
    "framework": {
      "name": "Microsoft.AspNetCore.App",
      "version": "5.0.0"
    },
    "runtimeOptions": {
      "configProperties": {
        "System.GC.HeapHardLimit": 1000000000
      }
    },
    "configProperties": {
      "System.GC.Server": true,
      "System.Reflection.Metadata.MetadataUpdater.IsSupported": false,
      "System.Runtime.Serialization.EnableUnsafeBinaryFormatterSerialization": false
    }
  }
}
```

The memory still goes beyond 1GB and stays like this until I process more data and it is finally reclaimed.

- **IIS application pool memory limit** - setting the memory limit on the application pool will cause it to be recycled, not forcing the GC to act faster