On Fri, Jun 3, 2016 at 12:39 PM, Andres Freund <and...@anarazel.de> wrote: > On 2016-06-03 12:31:58 -0400, Robert Haas wrote: >> Now, what varies IME is how much total RAM there is in the system and >> how frequently they write that data, as opposed to reading it. If >> they are on a tightly RAM-constrained system, then this situation >> won't arise because they won't be under the dirty background limit. >> And if they aren't writing that much data then they'll be fine too. >> But even putting all of that together I really don't see why you're >> trying to suggest that this is some bizarre set of circumstances that >> should only rarely happen in the real world. > > I'm saying that if that happens constantly, you're better off adjusting > shared_buffers, because you're likely already suffering from latency > spikes and other issues. Optimizing for massive random write throughput > in a system that's not configured appropriately, at the cost of well > configured systems to suffer, doesn't seem like a good tradeoff to me.
I really don't get it. There's nothing in any set of guidelines for setting shared_buffers that I've ever seen which would cause people to avoid this scenario. You're the first person I've ever heard describe this as a misconfiguration. > Note that other operating systems like windows and freebsd *alreaddy* > write back much more aggressively (independent of this change). I seem > to recall you yourself being quite passionately arguing that the linux > behaviour around this is broken. Sure, but being unhappy about the Linux behavior doesn't mean that I want our TPS on Linux to go down. Whether I like the behavior or not, we have to live with it. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers