On Thu, Apr 3, 2014 at 09:01:08PM +0300, Heikki Linnakangas wrote: > >Is there something I can set in the PGSQL parameters or in the file > >system parameters to force a steady flow of writes to disk rather > >than waiting for a sync system call? Mounting with "commit=1" did not > >make a difference. > > Try setting the vm.dirty_bytes sysctl. Something like 256MB might be a > good starting point. > > This comes up fairly often, see e.g.: > http://www.postgresql.org/message-id/flat/27C32FD4-0142-44FE-8488-9F36 > 6DC75966@xxxxxxxxxxxxxx Uh, should he set vm.dirty_bytes or vm.dirty_background_bytes? It is my understanding that vm.dirty_background_bytes starts the I/O while still accepting writes, while vm.dirty_bytes stops accepting writes during the I/O, which isn't optimal. See: https://www.kernel.org/doc/Documentation/sysctl/vm.txt dirty_bytes Contains the amount of dirty memory at which a process generating disk writes will itself start writeback. dirty_background_bytes Contains the amount of dirty memory at which the background kernel flusher threads will start writeback. I think we want the flusher to be active, not necessarly the writing process. -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
