On Fri, Apr 08, 2022 at 02:02:23PM -0700, Greg A. Woods wrote:
> Single Level Storage is an awesome concept and removes so many ugly
> hacks from algorithms that otherwise have to process data in files.
> Doing data processing with read and write and pipes is effectively
> working through a straw whereas SLS allows all (reasonably sized) data
> to be presented in entirely complete randomly accessible arrays just by
> attaching a "file" to a segment.  Mmap() is a very poor replacement that
> requires a great deal extra bookkeeping that's next to impossible to
> hide from; and also there's the problem of the consistency semantics
> being different between the I/O based filesystems and direct memory
> mapping of their files, which Mmap() reveals, and which SLS eliminates
> (by simply not having any I/O mechanism for files in the first place!).

To be fair, Multics had it a lot easier, because core memory meant
that every single memory access could be considered "durable storage",
so there was no real need for "fsync(2)" or "msync(2)".