On Sat, 2005-01-01 at 17:01, Bruce Momjian wrote: > Simon Riggs wrote: > > > Well, I think we're saying: its not in 8.0 now, and we take our time to > > consider patches for 8.1 and accept the situation that the parameter > > names/meaning will change in next release. > > I have no problem doing something for 8.0 if we can find something that > meets all the items I mentioned. > > One idea would be to just remove bgwriter_percent. Beta/RC users would > still have it in their postgresql.conf, but it is commented out so it > should be OK. If they uncomment it their server would not start but we > could just tell testers to remove it. I see that as better than having > conflicting parameters.
Can't say I like that at first thought. I'll think some more though... > Another idea is to have bgwriter_percent be the percent of the buffer it > will scan. Hmmm....well that was my original suggestion (bg2.patch on 12 Dec) (...though with a bug, as Neil pointed out) > We could default that to 50% or 100%, but we then need to > make sure all beta/RC users update their postgresql.conf with the new > default because the commented-out default will not be correct. ...we just differ/ed on what the default should be... > At this point I see these as our only two viable options, aside from > doing nothing. > I realize our current behavior requires a full scan of the buffer cache, > but how often is the bgwriter_maxpages limit met? If it is not a full > scan is done anyway, right? Well, if you heavy a very heavy read workload then that would be a problem. I was more worried about concurrency in a heavy write situation, but I can see your point, and agree. (Idea #1 still suffers from this, so we should rule it out...) > It seems the only way to really add > functionality is to change bgwriter_precent to control how much of the > buffer is scanned. OK. I think you've persuaded me on idea #2, if I understand you right: bgwriter_percent = 50 (default) bgwriter_maxpages = 100 (default) percent is the number of shared_buffers we scan, limited by maxpages. (I'll code it up in a couple of hours when the kids are in bed) -- Best Regards, Simon Riggs ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend