I ran a test of my own devising, in which I wrote a trivial C program
that calculates the square of a number using a quadratic algorithm,
built it, and ran it under both the old and new kernels.  Here are the
results:

[2.6.35-28 kernel]
chad@siga-asus:~/temp/testing$ time ./a.out 20000
The square of 20000, calculated very slowly, is 400000000

real    0m1.045s
user    0m1.040s
sys     0m0.000s


[2.6.38-8 kernel]
chad@siga-asus:~/temp/testing$ time ./a.out 20000
The square of 20000, calculated very slowly, is 400000000

real    0m53.264s
user    0m49.130s
sys     0m3.100s


Since the "real" time is roughly the sum of "user" and "sys", this seems to be 
a confirmation that the CPU is the problem, rather than memory or I/O 
transfers.  More interestingly, the "user" time dominating the "sys" time, 
which seems to indicate that it is not just system calls that are running at a 
glacial pace.

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https://bugs.launchpad.net/bugs/793437

Title:
  Unusable  Slowness In 2.6.38-8

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