Added to TODO: * Be more aggressive about creating WAL files
http://archives.postgresql.org/pgsql-hackers/2007-10/msg01325.php --------------------------------------------------------------------------- Tom Lane wrote: > Greg Smith <[EMAIL PROTECTED]> writes: > > On Fri, 26 Oct 2007, ITAGAKI Takahiro wrote: > >> Mixed usage of buffered and direct i/o is legal, but enforces complexity > >> to kernels. If we simplify it, things would be more relaxed. For > >> example, dropping zero-filling and only use direct i/o. Is it possible? > > > It's possible, but performance suffers considerably. I played around with > > this at one point when looking into doing all database writes as sync > > writes. Having to wait until the entire 16MB WAL segment made its way to > > disk before more WAL could be written can cause a nasty pause in activity, > > even with direct I/O sync writes. Even the current buffered zero-filled > > write of that size can be a bit of a drag on performance for the clients > > that get caught behind it, making it any sort of sync write will be far > > worse. > > This ties into a loose end we didn't get to yet: being more aggressive > about creating future WAL segments. ISTM there is no good reason for > clients ever to have to wait for WAL segment creation --- the bgwriter, > or possibly the walwriter, ought to handle that in the background. But > we only check for the case once per checkpoint and we don't create a > segment unless there's very little space left. > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 1: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to [EMAIL PROTECTED] so that your > message can get through to the mailing list cleanly -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://postgres.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
