Re: [PATCH] modules: Take a shortcut for checking if an address is in a module

[Ingo Molnar <mingo@elte.hu>]

* Vegard Nossum <vegard.nossum@gmail.com> wrote:

> >  > > Various pieces of the kernel (lockdep, latencytop, etc) tend to 
> >  > > store backtraces, sometimes at a relatively high frequency. In 
> >  > > itself this isn't a big performance deal (after all you're 
> >  > > using diagnostics features), but there have been some 
> >  > > complaints from people who have over 100 modules loaded that 
> >  > > this is a tad too slow.
> 
> Would it be overkill to simply drop the module addresses in an rbtree 
> and use that instead of a linear search over all the modules?
> 
> It would probably take a fair number of lines in C, and with a little 
> memory overhead, but the speed-up should be great. Should I give it a 
> try? (It would be arch-independent too.)

that's a tempting idea. rbtrees seem to be equally robust to plain lists 
in my experience, so i'd not find the extra complexity a showstopper, as 
long as the changes are well-tested. (radix trees on the other hand ... 
;-)

Rusty, Peter, Linus, any fundamental objections to Vegard's idea? Being 
able to take a transparent stack-trace signature for debugging or 
instrumentation purposes is important and performance does matter there 
IMO.

	Ingo