Jan Wieck wrote: > Bruce Momjian wrote: > > > Jan Wieck wrote: > >> >> > If the background cleaner has to not just write() but write/fsync or > >> >> > write/O_SYNC, it isn't going to be able to clean them fast enough. It > >> >> > creates a bottleneck where we didn't have one before. > >> >> > > >> >> > We are trying to eliminate an I/O storm during checkpoint, but the > >> >> > solutions seem to be making the non-checkpoint times slower. > >> >> > > >> >> > >> >> It looks as if you're assuming that I am making the backends unable to > >> >> write on their own, so that they have to wait on the checkpointer. I > >> >> never said that. > >> > > >> > Maybe I missed it but are those backend now doing write or write/fsync? > >> > If the former, that is fine. If the later, it does seem slower than it > >> > used to be. > >> > >> In my all_performance.v4.diff they do write and the checkpointer does > >> write+sync. > > > > Again, sorry to be confusing --- I might be good to try write/fsync from > > the background writer if backends can do writes on their own too without > > fsync. The additional fsync from the background writer should reduce > > disk writing during sync(). (The fsync should happen with the buffer > > unlocked.) > > No, you're not. But thank you for suggesting what I implemented.
OK, I did IM with Jan and I understand now --- he is using write/sync for testing, but plans to allow several ways to force writes to disk occasionally, probably defaulting to fsync on most platforms. Backend will still use write only, and a checkpoint will continue using sync(). The qustion still open is whether we can push most/all writes into the background writer so we can use fsync/open instead of sync. My point has been that this might be hard to do with the same performance we have now. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
