On Thu, Nov 24, 2016 at 12:41 AM, Tsunakawa, Takayuki <tsunakawa.ta...@jp.fujitsu.com> wrote: > From: pgsql-hackers-ow...@postgresql.org >> [mailto:pgsql-hackers-ow...@postgresql.org] On Behalf Of Tom Lane >> 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. > > I'm sorry for my late reply, yesterday was a national holiday in Japan. > > It's not FUD. I understand you hit the slow stats file write problem during > some regression test. You said it took 57 seconds to write the stats file > during the postmaster shutdown. That caused pg_ctl stop to fail due to its > 60 second timeout. Even the regression test environment suffered from the > trouble.
+1. -- 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
