Re: Release postmaster working memory context in slotsync worker

On Sat, Feb 28, 2026 at 2:58 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2026-02-28 01:25:12 +0900, Fujii Masao wrote:
> >> Child processes do not need the postmaster's working memory context and
> >> release it at the start of their main function. However, the slotsync worker
> >> appears to have missed this step.
>
> > Obviously this inconsistency is not good. However:
> > I think we should consider *not* releasing postmaster memory. Freeing the
> > memory actually can lead to an *increase* in memory usage and a slight
> > *decrease* in connection startup performance. The reason for that is that with
> > fork, memory allocated in postmaster is handled by copy-on-write in the
> > children.
>
> Meh. I think that's optimizing for the wrong thing. To my mind the
> point of releasing that context is to be sure that child processes
> don't have access to postmaster-private data.

Okay, I've included this point in the commit message of the patch.

> Admittedly, we're not
> doing anything as drastic as zeroing out the memory, but it'll soon
> be overwritten as the child starts up and populates its caches.

Yes.

Attached is a rebased version of the patch. I'm thinking to commit it.

Regards,

--
Fujii Masao