Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/

[Paul Jackson <pj@engr.sgi.com>]

> I added likely() and unlikely() to all tests, here are the results from 3 
> runs on my box : 

Any chance you could summarize what these results are, for those
of us too lazy to parse it all out?  The time spent by one author
to summarize in English what the numbers state can save the time of
a hundred readers each individually having to parse the numbers.

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.

If I'm reading this right, and if these results are valid, then we are
going about this optimization all wrong, at least if your CPU is an
AMD Athlon (T-bird). Weird.  Instead of stripping the "if (p)" test, we
should be changing it to "if (likely(p))", regardless of whether it
is very likely, or unlikely, or in between.  That is not what I would
call intuitive.

-- 
                  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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