From: ahemavathy (ahemavathy_at_hotmail.com)
Date: Wed Jan 21 2004 - 12:53:55 PST
I found this paper very interesting to read. It is well written and the language is simple.. it is easy to follow the authors. Of all the papers that we have read so far I found this most interesting maybe because it is applicable to current problems.
The paper describes Nooks, a new reliablity layer intended to significantly reduce extension-related failures. It is supposed to be a transparent layer between the kernel and the kernel extensions, isolating drivers within lightweight protection domains preventing them from corrupting the kernel. The Nooks Isolation Manager (NIM) performs the following functions 1) Isolation 2) Interposition 3) Object tracking and 4) Recovery. Then the paper describes how each of the functions have been implemented. I am convinced that although the implementation has limitations, the resulting Nooks protected kernel is an ideal solution to prevent most of the system crashes.
The test results show that Nooks eliminated 99% of the system crashes. The author's explanation of the difference between interrupt oriented and process oriented extensions and how Linux differently treats them differently is very interesting (maybe shocking). Also interesting to note were the latent bugs that were detected by the use of Nooks. Finally the authors try to measure the performance hit due to the additional transparent layer. Since for the majority of the commonly used extension system are simple drivers and sound cards, the performance hit of less than 10% is a very good tradeoff.
Overally I am really for the Nooks and curious to know whether any projects have been started as an outcome of the paper.
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