On Thu, Mar 1, 2018 at 1:54 PM, Andres Freund <and...@anarazel.de> wrote: > So this is hardcoded, without any sort of cache pressure logic? Doesn't > that mean we'll often *severely* degrade performance if a backend is > idle for a while?
Well, it is true that if we flush cache entries that haven't been used in a long time, a backend that is idle for a long time might be a bit slow when (and if) it eventually becomes non-idle, because it may have to reload some of those flushed entries. On the other hand, a backend that holds onto a large number of cache entries that it's not using for tens of minutes at a time degrades the performance of the whole system unless, of course, you're running on a machine that is under no memory pressure at all. I don't understand why people keep acting as if holding onto cache entries regardless of how infrequently they're being used is an unalloyed good. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
