On 2014-08-27 10:32:19 -0400, Aidan Van Dyk wrote: > On Wed, Aug 27, 2014 at 3:32 AM, Fabien COELHO <coe...@cri.ensmp.fr> wrote: > > > > > Hello Andres, > > > > [...] > >> > >> I think you're misunderstanding how spread checkpoints work. > >> > > > > Yep, definitely:-) On the other hand I though I was seeking something > > "simple", namely correct latency under small load, that I would expect out > > of the box. > > > > What you describe is reasonable, and is more or less what I was hoping > > for, although I thought that bgwriter was involved from the start and > > checkpoint would only do what is needed in the end. My mistake. > > > > > If all you want is to avoid the write storms when fsyncs start happening on > slow storage, can you not just adjust the kernel vm.dirty* tunables to > start making the kernel write out dirty buffers much sooner instead of > letting them accumulate until fsyncs force them out all at once?
Well. For one that's a os specific global tunable requiring root to be adjustable. For another we actually do want some buffering: If a backend writes out a buffer's data itself (happens very frequently) it *should* get buffered... So I don't think a process independent tunable is going to do the trick. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
