runtime: Huge memory usage regression in dotnet 7 on linux

Description

A dotnet 7 application consumes much more memory on linux than a dotnet 6 or dotnet 5 application.

After upgrading our application to dotnet 7 we noticed a huge increase in memory consumption in linux, services that used 100 MB were now using twice that amount.

The base issue can be easily reproduced

1. create new console application
2. make sure it does not exit instantly, e.g. by using a while loop like:

while (true)
{
    Console.WriteLine("Hello, World!");
    Thread.Sleep(TimeSpan.FromSeconds(1));
}

1. Verify that in your .csproj file you are targeting dotnet 7:

<TargetFramework>net7.0</TargetFramework>

1. Switch to a Release configuration
2. Start it under linux, e.g. by select WSL in the dropdown to launch it.
3. Verify the used memory, e.g. by running ps aux in your wsl shell and taking a look at the RSS column:

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root      5335  2.5  0.4 273549912 103944 pts/6 Sl+ 17:17   0:00 /usr/bin/dotnet /mnt/c/projects/sources/DotNet7Test/DotNet7Test/bin/Release/net7.0/DotNet7Test.dll

1. Realize in horror that the console process consumes 100+ MB
2. Stop the debugging
3. Target dotnet 6 by updating your csproj file to:

<TargetFramework>net6.0</TargetFramework>

1. Start it under linux, e.g. by select WSL in the dropdown to launch it.
2. Verify the used memory, e.g. by running ps aux in your wsl shell and taking a look at the RSS column:

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root      5383  1.0  0.0 2961956 25504 pts/6   Sl+  17:21   0:00 /usr/bin/dotnet /mnt/c/projects/sources/DotNet7Test/DotNet7Test/bin/Release/net6.0/DotNet7Test.dll

1. Wonder why the same process consumes only 25MB using dotnet 6.

Configuration

Dotnet 7 on Linux x64, see above

Regression?

Yes, this is a major performance regression in dotnet 7 compared to dotnet 5 or 6.

Other information

Notes: The memory consumption on windows on dotnet 7 is reasonable - it’s just a little higher, but not by crazy amounts. The difference between dotnet 5 and dotnet 6 on linux is negliable.

Take care, Martin