On Wed, Aug 27, 2014 at 10:10 AM, Claudio Freire <klaussfre...@gmail.com> wrote: > On Wed, Aug 27, 2014 at 6:05 AM, Fabien COELHO <coe...@cri.ensmp.fr> wrote: >>> [...] What's your evidence the pacing doesn't work? Afaik it's the fsync >>> that causes the problem, not the the writes themselves. >> >> >> Hmmm. My (poor) understanding is that fsync would work fine if everything >> was already written beforehand:-) that is it has nothing to do but assess >> that all is already written. If there is remaining write work, it starts >> doing it "now" with the disastrous effects I'm complaining about. >> >> When I say "pacing does not work", I mean that things where not written out >> to disk by the OS, it does not mean that pg did not ask for it. >> >> However it does not make much sense for an OS scheduler to wait several >> minutes with tens of thousands of pages to write and do nothing about it... >> So I'm wondering. > > Maybe what's needed, is to slightly tweak checkpoint logic to give the > kernel some time to flush buffers. > > Correct me if I'm wrong, but the checkpointer does the sync right > after the reads. Of course there will be about 30s-worth of > accumulated writes (it's the default amount of time the kernel holds > on to dirty buffers). > > Perhaps it should be delayed a small time, say 30s, to let the kernel > do the writing on its own.
Errata: just after the writes :-p -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers