> The two alternative algorithms are similar, but have these > differences: > The former (option (2)) finds a constant number of dirty pages, though > has varying search time.
This has the disadvantage of converging against 0 dirty pages. A system that has less than maxpages dirty will write every page with every bgwriter run. > The latter (option (3)) has constant search > time, yet finds a varying number of dirty pages. This might have the disadvantage of either leaving too much for the checkpoint or writing too many dirty pages in one run. Is writing a lot in one run actually a problem though ? Or does the bgwriter pause periodically while writing the pages of one run ? If this is expressed in pages it would naturally need to be more than the current maxpages (to accomodate for clean pages). The suggested 2% sounded way too low for me (that leaves 98% to the checkpoint). Also I think we are doing too frequent checkpoints with bgwriter in place. Every 15-30 minutes should be sufficient, even for benchmarks. We need a tuned bgwriter for this though. Andreas ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
