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SubjectRe: [RESEND PATCH 0/11] kernel:lockdep:replace DFS with BFS
From
2009/7/16 Peter Zijlstra <a.p.zijlstra@chello.nl>:
>
> I've asked several times to comment on the removal of that generation
> count DaveM did. Is that a normal part of DFS, or was that an
> optimization on top particular to this problem, can something similar be
> done for BFS, etc.

DFS uses generation count DaveM did to decide if a class is visted, and BFS
uses bitmap to mark a class is visted or not and the extra efficiency loss is

bitmap_zero(bfs_accessed, MAX_LOCKDEP_ENTRIES);

before staring each BFS.

On most of ARCH, bimap_zero can be optimizied to only consume very few
instructions,
can't it?

It seems bitmap is more easily used in BFS than generation count.

>
> Other than that it does seem to hold up, I've got the patches running on
> my laptop. Don't worry they're not getting lost.

Great.

--
Lei Ming


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