[o11c]

On Linux, that's exactly what `memfd` seals are for.

That said, even without seals, it's often possible to guarantee that you only read the memory once; in this case, even if the memory is technically mutating after you start, it doesn't matter since you never see any inconsistent state.

[murderfs]

It is very easy for zero-copy IPC using sealed memfd to be massively slower than just copying, because of the cost associated with doing a TLB shootdown on munmap. In order to see a benefit over just writing into a pipe, you'd likely need to be sending gigantic blobs, mapping them in both the reader and write into an address space that isn't shared with any other threads that are doing anything, and deferring and batching munmapping (and Linux doesn't really provide you an actual way to do this, aside from mapping them all in consecutive pages with MAP_FIXED and munmapping multiple mappings with a single call).

Any realistic high-performance zero copy IPC mechanism needs to avoid changing the page tables like the plague, which means things like memfd seals aren't really useful.

[kragen]

Thanks for the reference! I had been wondering if there was a way to do this on Linux for years. https://lwn.net/Articles/591108/ seems to be the relevant note?