[cb321]

Yeah.. FlexSC / Soares is my favorite paper from OSDI 2010. The system call batching with "looped" multi-call they mention there relates to the roughly 30 line (not actually looping) assembly language in my other comment here (https://news.ycombinator.com/item?id=39189135) and in a few ways pre-saged io_uring work.

Anyway, a 20-line example of a program written against said interpreter is https://github.com/c-blake/batch/blob/1201eefc92da9121405b79... but that only needs the wdcpy fake syscall not the conditional jump forward (although that could/should be added if the open can succeed but the mmap can fail and you want the close clean-up also included in the batch, etc., etc.).

I believe Cassyopia (also mentioned in Soares) hoped to be able to analyze code in user-space with compiler techniques to automagically generate such programs, but I don't know that the work ever got beyond a HotOS paper (i.e. the kinda hopes & dreams stage) and it was never clear how fancy the anticipated batches being. The Xen/VMware multi-calls Soares2010 also mentions do not seem to have inline copy/jumps, though I'd be pretty surprised if that little kernel module is the only example of it.