On Sat, Nov 27, 2010 at 2:27 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > For testing purposes, I figured that what I wanted to stress was > postgres process swapping and shmem access. I built current git HEAD > with --enable-debug and no other options, and tested with these > non-default settings: > shared_buffers 1GB > checkpoint_segments 50 > fsync off > (fsync intentionally off since I'm not trying to measure disk speed). > The test machine has two dual-core Nehalem CPUs. Test case is pgbench > at -s 25; I ran several iterations of "pgbench -c 10 -T 60 bench" > in each configuration. > > And the bottom line is: if there's any performance benefit at all, > it's on the order of 1%. The best result I got was about 3200 TPS > with hugepages, and about 3160 without. The noise in these numbers > is more than 1% though. > > This is discouraging; it certainly doesn't make me want to expend the > effort to develop a production patch. However, perhaps someone else > can try to show a greater benefit under some other test conditions.
Hmm. Presumably in order to see a large benefit, you would need to have shared_buffers set large enough to thrash the TLB. I have no idea how big TLBs on modern systems are, but it'd be interesting to test this on a big machine with 8GB of shared buffers. -- 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
