James Bottomley <james.bottom...@hansenpartnership.com> wrote: >> We start by creating a chunk of shared memory that all processes >> (we do not use threads) will have mapped at a common address, >> and we read() and write() into that chunk. > > Yes, that's what I was thinking: it's a cache. About how many > files comprise this cache? Are you thinking it's too difficult > for every process to map the files?
It occurred to me that I don't remember seeing any indication of how many processes we're talking about. There is once process per database connection, plus some administrative processes, like the checkpoint process and the background writer. At the low end, about 10 processes would be connected to the shared memory. The highest I've personally seen is about 3000; I don't know how far above that people might try to push it. I always recommend a connection pool to limit the number of database connections to something near ((2 * core count) + effective spindle count), since that's where I typically see best performance; but people don't always do that. -- Kevin Grittner EDB: 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
