fix(neonctl): set effective_io_concurrency to 0 on macos

[skyzh]

Problem

Postgres doesn't start with

2025-01-13 18:19:06.437 GMT [18213] DETAIL:  effective_io_concurrency must be set to 0 on platforms that lack posix_fadvise().

Summary of changes

Set the config item to 0 on macOS by default.

[knizhnik]

Sorry, we build Postgres at MacOS with -DUSE_PREFETCH:

else ifeq ($(UNAME_S),Darwin)
	PG_CFLAGS += -DUSE_PREFETCH

Setting this flag actually disable this check:

bool
check_effective_io_concurrency(int *newval, void **extra, GucSource source)
{
#ifndef USE_PREFETCH
	if (*newval != 0)
	{
		GUC_check_errdetail("\"%s\" must be set to 0 on platforms that lack support for issuing read-ahead advice.",
							"effective_io_concurrency");
		return false;
	}
#endif							/* USE_PREFETCH */
	return true;
}

So looks like for some reasons Darwin is not reported by name in your case.

[skyzh]

Oh, seems like it's because I didn't reconfigure Postgres

[skyzh]

Regardless I still prefer to get this patch merged because the fake cplane code should provide a correct config instead of relying on the Postgres code to automatically overwrite the value.

[knizhnik]

Regardless I still prefer to get this patch merged because the fake cplane code should provide a correct config instead of relying on the Postgres code to automatically overwrite the value.

Sorry, I do not completely understand the concern.
But for testing purposes it is definitely better and more convenient to have prefetch enabled (and working) at MacOS.

I performing many tests and experiments with prefetch at MacOS and explicit changing of effective_io_concurrency in each case is very invonvenient.

So I really prefer to leave everything as it is.

[github-actions]

7304 tests run: 6934 passed, 0 failed, 370 skipped (full report)

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Code coverage* (full report)

• functions: 32.7% (8057 of 24666 functions)
• lines: 47.8% (67021 of 140345 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
9e860e3 at 2025-01-13T20:16:33.052Z :recycle:}