9 Apr
2022
9 Apr
'22
5:34 a.m.
On 4/8/22, Greg A. Woods <woods(a)robohack.ca> 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!).
I think it's useful to have both I/O and memory views for files.
Things like commands that work equally well whether stdout is a disk
file or something like a pipe wouldn't work so well in a system where
disk files can only be accessed through a memory-like interface.
However, I guess the I/O interface could just be implemented with
library functions rather than real I/O syscalls for disk-like files.
Maybe I could try doing something like that in my OS but I'm not
completely sure if it would affect performance because it will be
QNX-like, and reads and writes would probably require the VFS to act
as an intermediary sometimes whereas that wouldn't be the case with
I/O since reads and writes would otherwise map onto kernel message
passing without any intermediary servers.