3 ms·

The linux sysctl is a wrapper for kernel state represented in the file system, freebsd sysctl is direct to kernel. So that is nice, everything in one place. B

by woodman 12y ago

The linux sysctl is a wrapper for kernel state represented in the file system, freebsd sysctl is direct to kernel. So that is nice, everything in one place. Before my switch to freebsd, I had been a linux user since 2000 - and while I was aware of the existence of sysctl, I don't remember seeing it used very often. It was much more common to see direct interaction with stuff in /proc (rockectraid, never again). Why is that? Is it an issue with standardizing driver interaction or what? My prior post wasn't written as a statement of exclusivity, simply that I prefer the way freebsd does it.

caf 12y ago
The /proc/sys/ and sysctl(2) methods are really just down to which syscall is used to talk to the kernel - either way it's just reading or writing a kernel-side data structure, there's no fundamental difference there. The /proc/sys/ pseudo-filesystem interface has the advantage that it's discoverable. The sysctl(2) interface requires userspace to have knowledge of a swag of hardcoded ID numbers identifying each node in the sysctl tree.
- woodman 12y ago
  I haven't poked through the code, but the linux man page isn't encouraging: "use the /proc/sys interface instead" [0] Compare that to the freebsd man page [1] [0] http://man7.org/linux/man-pages/man2/sysctl.2.html#NOTES http://man7.org/linux/man-pages/man2/sysctl.2.html#NOTES [1] https://www.freebsd.org/cgi/man.cgi?query=sysctl&sektion=3&manpath=FreeBSD+10.1-RELEASE https://www.freebsd.org/cgi/man.cgi?query=sysctl&sektion=3&m...
  - caf 12y ago
    I think perhaps we might be talking at cross-purposes here. My point is that when you call write(2) under Linux on a file descriptor derived from opening a /proc/sys pseudo-file you are talking directly to the kernel code responsible for updating the sysctl variables in the same way as you are when you call sysctl(2) under FreeBSD. The /proc/sys files aren't real files - they're just a way of representing the sysctl variables in the existing file namespace.
    - woodman 12y ago
      Ah, when you said sysctl(2) I thought you were talking about the linux call - which is basically dead code. Yeah I don't really have a beef with the whole "everything is a file" design, I actually quite like it, but I really like how well freebsd has done sysctl - both the subroutine (3) and the command (8).

by woodman 12y ago

caf 12y ago

The /proc/sys/ and sysctl(2) methods are really just down to which syscall is used to talk to the kernel - either way it's just reading or writing a kernel-side data structure, there's no fundamental difference there. The /proc/sys/ pseudo-filesystem interface has the advantage that it's discoverable. The sysctl(2) interface requires userspace to have knowledge of a swag of hardcoded ID numbers identifying each node in the sysctl tree.

woodman 12y ago
I haven't poked through the code, but the linux man page isn't encouraging: "use the /proc/sys interface instead" [0] Compare that to the freebsd man page [1] [0] http://man7.org/linux/man-pages/man2/sysctl.2.html#NOTES http://man7.org/linux/man-pages/man2/sysctl.2.html#NOTES [1] https://www.freebsd.org/cgi/man.cgi?query=sysctl&sektion=3&manpath=FreeBSD+10.1-RELEASE https://www.freebsd.org/cgi/man.cgi?query=sysctl&sektion=3&m...
- caf 12y ago
  I think perhaps we might be talking at cross-purposes here. My point is that when you call write(2) under Linux on a file descriptor derived from opening a /proc/sys pseudo-file you are talking directly to the kernel code responsible for updating the sysctl variables in the same way as you are when you call sysctl(2) under FreeBSD. The /proc/sys files aren't real files - they're just a way of representing the sysctl variables in the existing file namespace.
  - woodman 12y ago
    Ah, when you said sysctl(2) I thought you were talking about the linux call - which is basically dead code. Yeah I don't really have a beef with the whole "everything is a file" design, I actually quite like it, but I really like how well freebsd has done sysctl - both the subroutine (3) and the command (8).