Hi,
My observation is that kernels (inc. Minix3, Fiasco, and Pistachio) are often (sometimes much) larger than the official data. Maybe, they take different estimation methods? Or maybe the data are out of date? How about the headers and macros (which can notably influence loc.)?
I wonder if it can help if someone will measure and publish the loc. of these kernels with an unified and open standard. Of course, complete comparison between L4 and Minix3 is more valuable.
Regards,
Wei Shen
On 6/27/07, Gernot Heiser gernot@nicta.com.au wrote:
On Tue, 26 Jun 2007 17:39:51 +0200, "Neal H. Walfield" <
neal@walfield.org> said: NHW> Hendrik,
Could anybody explain why Fiasco is so big in comparison with Minix 3? From the difference in size I would expect that there is an essential difference in the feature set between Minix 3 and Fiasco. Or are the Minix lines just four times longer on average?
NHW> I recollect from a talk that Jorrit Herder gave about that Minix3 does NHW> not support paged memory: it uses segments for enforcing protection, NHW> which explains a large part of the difference you observe.
... which, among others, means that it cannot set up shared memory regions for high-bandwidth cross address-space communication.
The lack of portability has been mentioned too. Finally, L4 versions have a lot of fastpath code for low-latency IPC. My understanding is that Minix IPC is significantly slower than L4's. There are other optimisations in L4 implementations that add to the code size.
In general, you can always expect the need for a few extra things once a system moves from academia into the real world (as L4 has).
Having said that, Open Kernel Labs has stripped a fair bit of code from their OKL4 kernel (derived from Pistachio).
Gernot
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