[PATCH v3 2/5] benchtests: Add memset zero fill benchtest

[naohirot@fujitsu.com]

Hi Wilco,

> From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
> Sent: Tuesday, September 21, 2021 8:09 PM
>
> > What do you think?
> 
> As I've mentioned, this will never work using the current benchmark loop.
> At size 256 your loop has only 1 timer tick... The only way to get any data
> out is to increase the time taken per call. At 16K there are about 20 ticks so
> it is still very inaccurate. By repeating the test thousands of times you can
> some signal out (eg. 20% is 20 ticks, 80% is 21 gives ~20.8 ticks on average),
> but that's impossible for smaller sizes.
> 
> So if you want to measure small sizes, you need to use a more accurate timing
> loop.

Thank you for the comment.
OK, I understood. So I updated the start size to 16KB too to commit first.
Please find V5 [1] and merge it if it's OK.
Changes from V4:
- Start size to 16KB from 256B
- End size to 16MB from 64MB

[1] https://sourceware.org/pipermail/libc-alpha/2021-September/131245.html

Thanks.
Naohiro