Hi Tony,
Your description doesn't really explain what you want to use this
thing exactly for in userspace.
On Fri, Jul 29, 2011 at 12:48 AM, Tony Ibbs <tibs@xxxxxxxxxxxxxx> wrote:
> So why did we write it as a kernel module?
> ==========================================
> As implementors, a kernel module makes a lot of sense. Not least
> because:
>
> * It gives us a lot of things for free, including list handling,
> reference counting, thread safety and (on larger systems)
> multi-processor support, which we would otherwise have to write and
> debug ourselves. This also keeps our codebase smaller.
That's not a reason to put this into the kernel, really.
> * It helps give us reliability, partly because of the code we're
> relying on, partly because of the strictures of working in the
> kernel, partly by shielding us from userspace.
So now instead of crashing in userspace, we crash the kernel? This
seems like a bogus argument as well.
> * It reduces message copying (we have userspace to kernel back to
> userspace, as opposed to a userspace daemon communicating with
> clients via sockets)
Now this sounds like a real reason but you'd have to explain why you
can't reuse existing zero-copy mechanisms like splice() and tee().
> * It makes it simple for us to tell when a message recipient has "gone
> away", as the kernel will call our "release" callback for us.
Again, sounds like a reasonable technical requirement but doesn't
really justify putting all this code into the kernel.
> * It allows us to provide the functionality on systems without
> requiring anything much beyond /dev and maybe /proc in userspace.
Why is this important?
Pekka
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