On Tue, Jan 10, 2023 at 06:31:41AM +0000, Christophe Leroy wrote:
> Le 09/01/2023 à 21:51, Song Liu a écrit :
> > Do you mean one tree will cause addr_[min|max] to be inaccurate?
> >
>
> Yes at least. On powerpc you will have module text below kernel,
> somewhere between 0xb0000000 and 0xcfffffff, and you will have module
> data in vmalloc area, somewhere between 0xf0000000 and 0xffffffff.
>
> If you have only one tree, any address between 0xc0000000 and 0xefffffff
> will trigger a tree search.
The current min/max thing is tied to the tree because of easy update on
remove, but module-insert/remove is not a performance critical path.
So I think it should be possible to have {min,max}[TYPES] pairs. Either
brute force the removal -- using a linear scan of the mod->list to find
the new bounds on removal.
Or overengineer the whole thing and use an augmented tree to keep that
many heaps in sync during the update -- but this seems total overkill.
The only consideration is testing that many ranges in
__module_address(), this is already 2 cachelines worth of range-checks
-- which seems a little excessive.
(also, I note that module_addr_{min,max} are unused these days)
