Re: LWLock optimization for multicore Power machines

Alexander Korotkov <a.korotkov@postgrespro.ru> writes:
>> It seems that on this platform definition of atomics should be provided by
>> fallback.h.  But it doesn't because I already defined PG_HAVE_ATOMIC_U32_SUPPORT
>> in arch-ppc.h.  I think in this case we shouldn't provide ppc-specific
>> implementation of pg_atomic_fetch_mask_add_u32().  However, I don't know
>> how to do this assuming arch-ppc.h is included before compiler-specific
>> headers.  Thus, in arch-ppc.h we don't know yet if we would find
>> implementation of atomics for this platform.  One possible solution is to
>> provide assembly implementation for all atomics in arch-ppc.h.

> BTW, implementation for all atomics in arch-ppc.h would be too invasive and
> shouldn't be considered for v10.
> However, I made following workaround: declare pg_atomic_uint32 and
> pg_atomic_fetch_mask_add_u32_impl() only when we know that generic-gcc.h
> would declare gcc-based atomics.

I don't have a well-informed opinion on whether this is a reasonable thing
to do, but I imagine Andres does.

> Could you, please, check it on Apple PPC?

It does compile and pass "make check" on prairiedog.
        regards, tom lane