Re: "Enhanced" MD code avaible for review

From: Jeff Garzik
Date: Thu Mar 25 2004 - 20:07:54 EST

Justin T. Gibbs wrote:
I respectfully disagree with the EMD folks that a userland approach is
impossible, given all the failure scenarios.

I've never said that it was impossible, just unwise. I believe
that a userland approach offers no benefit over allowing the kernel
to perform all meta-data operations. The end result of such an
approach (given feature and robustness parity with the EMD solution)
is a larger resident side, code duplication, and more complicated
configuration/management interfaces.

There is some code duplication, yes. But the right userspace solution does not have a larger RSS, and has _less_ complicated management interfaces. A key benefit of "do it in userland" is a clear gain in flexibility, simplicity, and debuggability (if that's a word).

But it's hard. It requires some deep thinking. It's a whole lot easier to do everything in the kernel -- but that doesn't offer you the protections of userland, particularly separate address spaces from the kernel, and having to try harder to crash the kernel. :)


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