On Mon, Oct 29, 2018 at 11:34 PM, Alexey Dobriyan <adobri...@gmail.com> wrote: >> I'd much rather move to a model in which userspace *explicitly* tells >> the kernel which fields it wants, with the kernel replying with just >> those particular fields, maybe in their raw binary representations. >> The ASCII-text bag-of-everything files would remain available for >> ad-hoc and non-performance critical use, but programs that cared about >> performance would have an efficient bypass. One concrete approach is >> to let users open up today's proc files and, instead of read(2)ing a >> text blob, use an ioctl to retrieve specified and targeted information >> of the sort that would normally be encoded in the text blob. Because >> callers would open the same file when using either the text or binary >> interfaces, little would have to change, and it'd be easy to implement >> fallbacks when a particular system doesn't support a particular >> fast-path ioctl. > > You've just reinvented systems calls.
I don't know why you say so. There are important benefits that come from using an ioctl on a proc file FD instead of a plain system call. Procfs files have file permissions, auditing, SCM_RIGHTS-ability, PID race immunity, and other things that you wouldn't get from a plain "get this information about this PID" system call.
