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

* 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


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