Robert Haas <robertmh...@gmail.com> writes: > I agree. However, in many cases, the major cost of a fast shutdown is > getting the dirty data already in the operating system buffers down to > disk, not in writing out shared_buffers itself. The latter is > probably a single-digit number of gigabytes, or maybe double-digit. > The former might be a lot more, and the write of the pgstat file may > back up behind it. I've seen cases where an 8kB buffered write from > Postgres takes tens of seconds to complete because the OS buffer cache > is already saturated with dirty data, and the stats files could easily > be a lot more than that.
I think this is mostly FUD, because we don't fsync the stats files. Maybe we should, but we don't today. So even if we have managed to get the system into a state where physical writes are heavily backlogged, that's not a reason to assume that the stats collector will be unable to do its thing promptly. All it has to do is push a relatively small amount of data into kernel buffers. regards, tom lane -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers