Hi all, I recently tried a simple benchmark to see how far 9.4 had come since 8.4, but I discovered that I couldn't get 9.4 to even touch 8.4 for performance. After checking 9.2 and 9.3 (as per Kevin Grittner's suggestion), I found that those were fine, so the issue must be in 9.4devel. I used identical configurations for each test, and used 9.1's pgbench to ensure changes in pgbench didn't affect the outcome. The common config changes were:
max_connections = 500 shared_buffers = 4GB effective_cache_size = 12GB random_page_cost = 2.0 cpu_tuple_cost = 0.03 wal_buffers = 32MB work_mem = 100MB maintenance_work_mem = 512MB checkpoint_segments = 32 checkpoint_timeout = 15min checkpoint_completion_target = 0.8 commit_delay = 50 commit_siblings = 15 System info: 8GB DDR3 RAM (yes, I know the config isn't optimal here) 64-bit Linux Mint 15 (3.8.0 kernel) ext4 Only build option used was --enable-depend. I did have --enable-cassert for the shorter 5 min benchmarks, but was removed for the 30 min tests. Here are the results: pgbench -j 80 -c 80 -T 300: 8.4 - 535.990042 9.2 - 820.798141 9.3 - 828.395498 9.4 - 197.851720 pgbench -j 20 -c 20 -T 300: 8.4 - 496.529343 9.2 - 569.626729 9.3 - 575.831264 9.4 - 385.658893 pgbench -j 20 -c 400 -T 300: 8.4 - 580.186868 9.2 - 824.590252 9.3 - 784.638848 9.4 - 524.493308 These were only run for 5 minutes each, but subsequent ones were run for 30 mins. All tests were run with -s 20. Given a few key commits Robert Haas directed me to, I narrowed down the regression to a time period, so benchmarked a few select commits. pgbench -j 80 -c 80 -T 1800: 8.4: 812.482108 9.4 HEAD: 355.397658 9.4 e5592c (9th July): 356.485625 9.4 537227 (7th July): 365.992518 9.4 9b2543 (7th July): 362.587339 9.4 269e78 (5th July): 359.439143 9.4 8800d8 (5th July): 821.933082 9.4 568d41 (2nd July): 822.991160 269e78 was the commit immediately after 8800d8, so it appears that introduced the regression. "Use posix_fallocate() for new WAL files, where available." Ironically, that was intended to be a performance improvement. Regards Thom -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers