On Thu, Dec 21, 2006 at 06:46:36PM +0900, ITAGAKI Takahiro wrote: > > Oh, really, what an evil fsync is! Yes, I sometimes saw a backend > > waiting for lseek() to complete when it committed. But why does the > > backend which is syncing WAL/pg_control have to wait for syncing the > > data file? They are, not to mention, different files, and WAL and > > data files are stored on separate disks. > > Backends call lseek() in planning, so they have to wait fsync() to > the table that they will access. Even if all of data in the file is in > the cache, lseek() conflict with fsync(). You can see a lot of backends > are waiting in planning phase in checkpoints, not executing phase.
Hmm, there are other ways to sync parts of a file. For example doing an mmap()/msync()/munmap() cycle to start an asyncronous flush. But given what you're saying that might suffer from the same problem. Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to > litigate.
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