On Tue, Nov 30, 2004 at 10:57:02AM -0500, Tom Lane wrote: > Greg Stark <[EMAIL PROTECTED]> writes: > > Mark Wong <[EMAIL PROTECTED]> writes: > >> I have some initial results using 8.0beta5 with our OLTP workload. > >> http://www.osdl.org/projects/dbt2dev/results/dev4-010/199/ > >> throughput: 4076.97 > > > Do people really only look at the "throughput" numbers? Looking at those > > graphs it seems that while most of the OLTP transactions are fulfilled in > > subpar response times, there are still significant numbers that take as much > > as 30s to fulfil. > > > Is this just a consequence of the type of queries being tested and the data > > distribution? Or is Postgres handling queries that could run consistently > > fast > > but for some reason generating large latencies sometimes? > > Given the regular shape of the first graph (transactions/minute), > there's every reason to think that the slowdowns are caused by > checkpoint I/O storms. It would be worth the trouble to experiment > with adjusting the bgwriter parameters to even out the flow of write > operations. (I think I've already pointed out that the current defaults > for the bgwriter seem mighty conservative.) > > regards, tom lane
I do have bgwriter_delay increased to 10, per previous recommendation, which did smooth out the throughput graph considerably. I can continue to adjust those settings. Mark ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html