pmap_copy for ARMv6/v7

[Alan Cox]

On 05/28/2013 17:17, Zbigniew Bodek wrote:
> 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.


>From what you describe above, I think that you've done a reasonable job
of testing.  The performance results are in line with what I would
expect.  I wouldn't worry too much about obtaining further test results.


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


The patch looks fine.

Alan