On Fri, 2008-12-19 at 09:43 +0900, Fujii Masao wrote: > > Yes, please check the call points for ForceSyncCommit. > > > > Do I think every xlog flush should be synchronous, no, I don't. > That's why we have a user settable parameter for it. > > Umm.. I focus attention on XLogFlush() called except > RecordTransactionCommit(). > For example, FlushBuffer(), WriteTruncateXlogRec().. etc. These > XLogFlush() might > flush XLOG synchronously even if asynchronous commit case.
XLogFlush() flushes because of an interlock between a dirty buffer write and an outstanding WAL write. Dirty buffer writes are not replicated, so there is no need to have a similar interlock on WAL streaming. So making those call points synchronous is possible, but neither necessary or IMHO desirable. On a related but different point: We don't need an interlock between dirty buffers and WAL during recovery because the WAL has already been written. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
