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SubjectRe: no need to check for NULL before calling kfree() -fs/ext2/
Pekka wrote:
> (4) The cleanups Jesper and others are doing are to remove the
> _redundant_ NULL checks (i.e. it is now checked twice).

Even such obvious changes as removing redundant checks doesn't
seem to ensure a performance improvement. Jesper Juhl posted
performance data for such changes in his microbenchmark a couple
of days ago.

As I posted then, I could swear that his numbers show:

> Just looking at the third run, it seems to me that "if (likely(p))
> kfree(p);" beats a naked "kfree(p);" everytime, whether p is half
> NULL's, or very few NULL's, or almost all NULL's.

Twice now I have asked Jesper to explain this strange result.

I have heard no explanation (not even a terse "you idiot ;)"),
nor anyone else comment on these numbers.

Maybe we should be following your good advice:

> You don't know that until you profile!

instead of continuing to make these code changes.

--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <pj@engr.sgi.com> 1.650.933.1373, 1.925.600.0401
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