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

Andres Freund <andres(at)anarazel(dot)de> writes:
>> I landed on the idea of adding some intentional spinlock
>> contention to src/test/modules/test_shm_mq, which is a prefab test
>> framework for passing data among multiple worker processes. The
>> attached quick-hack patch makes it grab and release a spinlock once
>> per passed message.

> I wonder if this will show the full set of spinlock contention issues - isn't
> this only causing contention for one spinlock between two processes?

I don't think so -- the point of using the "pipelined" variant is
that messages are passing between all N worker processes concurrently.
(With the proposed test, I see N processes all pinning their CPUs;
if I use the non-pipelined API, they are busy but nowhere near 100%.)

It is just one spinlock, true, but I think the point is to gauge
what happens with N processes all contending for the same lock.
We could add some more complexity to use multiple locks, but
does that really add anything but complexity?

regards, tom lane