On Thu, Aug 28, 2014 at 3:27 AM, Fabien COELHO <coe...@cri.ensmp.fr> wrote: > Hello Aidan, > > >> 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? > > > I tried that by setting: > vm.dirty_expire_centisecs = 100 > vm.dirty_writeback_centisecs = 100 > > So it should start writing returned buffers at most 2s after they are > returned, if I understood the doc correctly, instead of at most 35s. > > The result is that with a 5000s 25tps pretty small load (the system can do > 300tps with the default configuration), I lost 2091 (1.7%) of transactions, > that is they were beyond the 200ms schedule limit. Another change is that > overall the lost transactions are more spread than without this setting, > although there still is stretches of unresponsiveness. > > So although the situation is significantly better, it is still far from good > with the much reduced value I tried.
What do the checkpoint logs look like now? (especially interested in sync times) -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
