On Wed, Jun 27, 2012 at 12:00 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.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?
It seemed more complicated. If we use the POSIX API, we've got to have code to find a non-colliding name for the shm, and we've got to arrange to clean it up at process exit. Anonymous shm doesn't require a name and goes away automatically when it's no longer in use. With respect to EXEC_BACKEND, I wasn't proposing to kill it, just to make it continue to use a full-sized sysv shm. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
