Re: Posix Shared Mem patch

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Posix Shared Mem patch
Date: 2012-06-27 04:00:49
Message-ID: 20486.1340769649@sss.pgh.pa.us
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> So, here's a patch. Instead of using POSIX shmem, I just took the
> expedient of using mmap() to map a block of MAP_SHARED|MAP_ANONYMOUS
> memory. The sysv shm is still allocated, but it's just a copy of
> PGShmemHeader; the "real" shared memory is the anonymous block. This
> won't work if EXEC_BACKEND is defined so it just falls back on
> straight sysv shm in that case.

Um. I hadn't thought about the EXEC_BACKEND interaction, but that seems
like a bit of a showstopper. I would not like to give up the ability
to debug EXEC_BACKEND mode on Unixen.

Would Posix shmem help with that at all? Why did you choose not to
use the Posix API, anyway?

regards, tom lane

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