On Tue, Mar 13, 2012 at 10:02 PM, Fujii Masao <masao.fu...@gmail.com> wrote: > On Wed, Mar 14, 2012 at 7:20 AM, Robert Haas <robertmh...@gmail.com> wrote: >> On Tue, Mar 13, 2012 at 3:48 PM, Robert Haas <robertmh...@gmail.com> wrote: >>> On Mon, Mar 12, 2012 at 4:45 PM, Jeff Janes <jeff.ja...@gmail.com> wrote: >>>> Rerunning all 4 benchmarks (both 16MB and 32MB wal_buffers on both >>>> machines) with fsync=off (as well as synchronous_commit=off still) >>>> might help clarify things. >>> >>> I reran the 32-client benchmark on the IBM machine with fsync=off and got >>> this: >>> >>> 32MB: tps = 26809.442903 (including connections establishing) >>> 16MB: tps = 26651.320145 (including connections establishing) >>> >>> That's a speedup of nearly a factor of two, so clearly fsync-related >>> stalls are a big problem here, even with wal_buffers cranked up >>> through the ceiling. >> >> And here's a tps plot with wal_buffers = 16MB, fsync = off. The >> performance still bounces up and down, so there's obviously some other >> factor contributing to latency spikes > > Initialization of WAL file? Do the latency spikes disappear if you start > benchmark after you prepare lots of the recycled WAL files?
The latency spikes seem to correspond to checkpoints, so I don't think that's it. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
