Count RAM usage of pipe generated by pipe() and fcntl(F_GETPIPE_SZ)

[oech3]

context: uutils/coreutils#11597

uutils/coreutils uses
https://github.com/uutils/coreutils/blob/0366d3c657ef02ff7c82dcd25926e0485db38ed2/src/uucore/src/lib/features/pipes.rs#L24-L31 to generate 1 MiB pipe used only from the process. However, CodSpeed does not count it as RAM usage since pipe is allocated by Linux kernel itself (not malloc).
I want to count them as RAM usage.

I know it is very rare usecase. But I think something like codspeed_ram_usage!(1024 * 1024); is more generic.

[GuillaumeLagrange]

Hello, indeed that would be interesting to track. We have a few improvements to the memory instrument planned. We'll see if there's a generic way to retrieve this memory allocation through sys call monitoring, else we may just add a declarative way for users to signal ram usage that we fail to detect automatically, although I'd like to avoid this.

[oech3]

fcntl returns pipe size (which might larger than requested size).
In my thought, this is same with requesting to count size of files on /tmp if /tmp is tmpfs.

[oech3]

Same issue for memfd_create?

[oech3]

In context of zero-copy, pipe size is not an actuall RAM usage, but I think we can detect it as page cash's generated by splice call.