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So what's the advantage of user space?

Jul 26, 2011, 10:00 (1 Talkback[s])
(Other stories by Linus Torvalds)

"From Linus Torvalds <>
Subject Re: [PATCH 08/13] iscsi-target: Add CHAP Authentication support using libcrypto
On Sat, Jul 23, 2011 at 9:39 AM, James Bottomley wrote:
> > I've asked you twice for input on the patch doing this in userspace,
> which was posted five weeks ago. Just ignoring something is
> unacceptable behaviour ... what do I have to do to get your attention?
> NAK the patch set?

So what's the advantage of user space?

Traditionally, kernel/userspace splits have been:

  • fragile as hell
  • more code
  • slower
  • complicated to set up
  • problematic with backwards compatibility issues

and these days when I see some kernel functionality that needs user space support, I just go "f*ck, that's going to be a pain".

So I think the "that part can be done in user space" argument is fundamentally crap.

Now, if it is an issue of "that can be done BETTER in user space BECAUSE xyz", then that's a different issue. I haven't seen that argument, though.


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