On Mon, Aug 9, 2010 at 2:33 PM, Bruce Momjian <br...@momjian.us> wrote: >> > Let me be more concrete. ?Suppose you are using threads, and you want to >> > increase your shared memory from 20MB to 30MB. ?How do you do that? ?If >> > you want it contiguous, you have to use realloc, which might move the >> > pointer. ?If you allocate another 10MB chunk, you then have shared >> > memory fragments, which is the same as adding another shared memory >> > segment. >> >> You probably wouldn't do either of those things. You'd just allocate >> small chunks here and there for whatever you need them for. > > Well, then we do that with shared memory then --- my point is that it is > the same problem with threads or processes.
Well, I think your point is wrong, then. :-) It's not the same at all. If you have a bunch of threads in one address space, "shared" memory is really just process-local. You can grow the total amount of allocated space just by calling malloc(). With our architecture, you can't. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise Postgres Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
