[vlovich123]

Rather than a direct syscall, you could imagine something like rseq where you have a shared userspace / kernel data structure where the userspace code gets aborted and restarted if the page was evicted while being processed. But making this work correctly and actually not have a perf overhead and also be an ergonomic API is super hard. In practice people who care probably are satisfied by direct I/O within io_uring with a custom page cache and a truly optimal implementation where the OS can still manage file pages and evict them but the application still new when it happened isn’t worth it.

[bcrl]

Unfortunately, a lot of the shared state with userland became much more difficult to implement securely when the Meltdown and Spectre (and others) exploits became concerns that had to be mitigated. They makes the OS's job a heck of a lot harder.

Sometimes I feel modern technology is basically a delicately balanced house of cards that falls over when breathed upon or looked at incorrectly.