pmap_copy for ARMv6/v7

[Zbigniew Bodek]

Hello Everyone,

I would like to share with you the patch adding pmap_copy()
functionality to pmap-v6.c. This is the last but not least of
the pmap improvements done as a part of Semihalf work on
Superpages support.

We tried various technics to test the patch on our target.
Apart from obvious long term stability tests and others,
we used a simple benchmark to measure fork system call time and overhead.

The program can be downloaded from here:
http://berlin.ccc.de/~packet/fork_test.c

A single fork time has increased as suspected (the program is not measuring
a real-life fork situation where child process is actually doing something)
but the average system overhead has decreased.
For 10000 fork(), 10000 vfork() and 10000 pthread_create() calls we observe
100000 less vm_faults and shorter overall test time.

If you have any suggestions or have an idea for benchmarking this
feature please share.

We will appreciate if you could test this patch on your ARM platforms and
send
us your review/feedback.

Best regards
Zbyszek Bodek
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