Re: Add spin_delay() implementation for Arm in s_lock.h

Hi Tom,

> What did you test exactly?

Tested 3 benchmark configurations on an m6g.16xlarge (Graviton2, 64 cpus, 256GB RAM)
I set the scale factor to consume about 1/3 of 256GB and the other parameters in the next line.
pgbench setup: -F 90 -s 5622 -c 256
Pgbench select-only w/   patch  662804 tps (-0.5%)
                                     w/o patch  666354 tps. 
                tcpb-like     w/   patch  35844 tps (0%)
                                    w/o patch  35835 tps

We also test with Hammerdb when evaluating patches, it shows the patch gets +3%:
Hammerdb (192 Warehouse 256 clients)
w/   patch 1147463 NOPM (+3%)
w/o patch 1112908 NOPM

I've run pgbench more than once and the measured TPS values overlap, even though the means on select-only show a small degradation at the moment I am concluding it is noise.  On Hammerdb, the results show a measurable difference.

Thanks,
Geoff