Re: Shared Memory: How to use SYSV rather than MMAP ?

Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> writes:
> Since it's not fixing a bug, we wouldn't back-patch that into existing
> releases. But I agree that we should do something like this for
> PostgreSQL 12, and I think we should make it user configurable.

I'm -1 on making this user configurable via a GUC; that adds documentation
and compatibility burdens that we don't need, for something of no value
to 99.99% of users. The fact that the default would need to be
platform-dependent just makes that tradeoff even worse. I think the other
0.01% who need to change the default (and are bright enough to be doing
the right thing for the right reasons) could certainly handle something
like a pg_config_manual.h control symbol --- see USE_PPC_LWARX_MUTEX_HINT
for a precedent that I think applies well here. So I'd favor just doing
it that way.

regards, tom lane