Hard, but apparently not impossible :-) [LWN.net]

Hard, but apparently not impossible :-)

Posted Apr 7, 2005 23:08 UTC (Thu) by lm (guest, #6402)
In reply to: Hard, but apparently not impossible :-) by emk
Parent article: Linus on the BK withdrawal

Perhaps it's because I've done significant work on kernels, X11, and written the better part of two different SCM systems. Oh, and compilers long ago. But not optimizers which may be where the really hard compier work lies. Working on BK is harder than any of those including multi-threading kernels.

It's certainly harder than all the things you listed in _my_ experience. And history has shown it not to be easy for anyone else either. Greg Stein's post nailed it: it's easy to get something that looks like it works, it's a lot harder to get something that always works.

We've counted more than 10,000 replicas of the Linux kernel in BK. More than 150,000 changesets over the 2.4/2.5/2.6 series. Making that work, where all of them synchronize with each other, using versions of BK that differ by years without having it all fall apart, yes, that's hard.

I'm sure one of the many open scm systems will get there some day but it's going to take a while and it's going to be no fun when they issue a new release that breaks your old repos, etc. Or they aren't around to answer the phone when it gets corrupted, etc.

I'm not saying you can't do it, you can. It's just hard. And not much fun once the thrill of having people use your code wears off and you have to stick around and support them. Please don't take this as looking for strokes or whatever else it is that I'll be accused of next, it's simply a statement that it is really hard and if you want a good answer it is going to take a lot of people a lot of time to get there. I don't care how good they are, I think I'm very good at this and I've done it twice already and it would take me years if I had to start over with everything I know now. It's hard, there are a zillion corner cases. None of which are very important in isolation but all of them added up are somewhat overwhelming.

You'll see. Whoever emerges as the person doing this work for you deserves a lot of your support. Please give it to him or her.

--lm

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