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Hi, I was doing some benchmarking while changing configuration
options to try to get more performance out of our postgresql servers and
noticed that when running pgbench against 8.4.3 vs 8.4.4 on identical hardware
and configuration there is a large difference in performance. I know tuning is
a very deep topic and benchmarking is hardly an accurate indication of real
world performance but I was still surprised by these results and wanted to know
what I am doing wrong. OS is CentOS 5.5 and the postgresql packages are from the pgdg
repo. Hardware specs are: 2x Quad core Xeons 2.4Ghz 16GB RAM 2x RAID1 7.2k RPM disks (slow I know, but we are upgrading
them soon..) Relevant Postgresql Configuration: max_connections = 1000 shared_buffers = 4096MB temp_buffers = 8MB max_prepared_transactions = 1000 work_mem = 8MB maintenance_work_mem = 512MB wal_buffers = 8MB checkpoint_segments = 192 checkpoint_timeout = 30min effective_cache_size = 12288MB Results for the 8.4.3
(8.4.3-2PGDG.el5) host: [root@some-host ~]# pgbench -h dbs3 -U postgres -i -s 100
pgbench1 > /dev/null 2>&1 && pgbench -h dbs3 -U postgres -c
100 -t 100000 pgbench1 starting vacuum...end. transaction type: TPC-B (sort of) scaling factor: 100 query mode: simple number of clients: 100 number of transactions per client: 100000 number of transactions actually processed:
10000000/10000000 tps = 5139.554921 (including connections establishing) tps = 5140.325850 (excluding connections establishing) opreport: CPU: Intel Core/i7, speed 2394.07 MHz (estimated) Counted CPU_CLK_UNHALTED events (Clock cycles when not
halted) with a unit mask of 0x00 (No unit mask) count 100000 CPU_CLK_UNHALT...| samples| %| ------------------ 37705832 61.3683 postgres 18472598 30.0652 no-vmlinux 4982274 8.1089 libc-2.5.so 138517 0.2254 oprofiled 134628 0.2191 libm-2.5.so 1465 0.0024 libc-2.5.so 1454 0.0024 libperl.so 793 0.0013
libdcsupt.so.5.9.2 444 7.2e-04
dsm_sa_datamgrd
CPU_CLK_UNHALT...|
samples| %|
------------------
401 90.3153 dsm_sa_datamgrd
43 9.6847 anon (tgid:8013 range:0xffffe000-0xfffff000) 410 6.7e-04
libxml2.so.2.6.26 356 5.8e-04 ld-2.5.so 332 5.4e-04
libnetsnmp.so.10.0.3 327 5.3e-04 dsm_sa_snmpd
CPU_CLK_UNHALT...|
samples| %|
------------------
255 77.9817 dsm_sa_snmpd
72 22.0183 anon (tgid:8146 range:0xffffe000-0xfffff000) 304 4.9e-04
libcrypto.so.0.9.8e 290 4.7e-04
libpthread-2.5.so 199 3.2e-04
libdcsmil.so.5.9.2 139 2.3e-04 modclusterd <snip> Results for the 8.4.4
(8.4.4-1PGDG.el5) host: [root@ some-host ~]# pgbench -h dbs4 -U postgres -i -s
100 pgbench1 > /dev/null 2>&1 && pgbench -h dbs4 -U postgres
-c 100 -t 100000 pgbench1 starting vacuum...end. transaction type: TPC-B (sort of) scaling factor: 100 query mode: simple number of clients: 100 number of transactions per client: 100000 number of transactions actually processed: 10000000/10000000 tps = 2765.643549 (including connections establishing) tps = 2765.931203 (excluding connections establishing) opreport: CPU: Intel Core/i7, speed 2394.07 MHz (estimated) Counted CPU_CLK_UNHALTED events (Clock cycles when not
halted) with a unit mask of 0x00 (No unit mask) count 100000 CPU_CLK_UNHALT...| samples| %| ------------------ 312481395 84.5038 postgres 41861164 11.3204 no-vmlinux 14290652 3.8646 libc-2.5.so 812148 0.2196 oprofiled 305909 0.0827 libm-2.5.so 7647 0.0021 libc-2.5.so 3809 0.0010
libdcsupt.so.5.9.2 3077 8.3e-04 libperl.so 2302 6.2e-04 dsm_sa_datamgrd
CPU_CLK_UNHALT...|
samples| %|
------------------
2113 91.7897 dsm_sa_datamgrd
189 8.2103 anon (tgid:8075 range:0xffffe000-0xfffff000) 2175 5.9e-04 libxml2.so.2.6.26 1455 3.9e-04 dsm_sa_snmpd
CPU_CLK_UNHALT...|
samples| %|
------------------
1226 84.2612 dsm_sa_snmpd
229 15.7388 anon (tgid:8208 range:0xffffe000-0xfffff000) 1227 3.3e-04 libdchipm.so.5.9.2 1192 3.2e-04 libpthread-2.5.so 804 2.2e-04
libnetsnmp.so.10.0.3 745 2.0e-04 modclusterd <snip> Any input? I can reproduce these numbers consistently. If
you need more information then just let me know. By the way, I am a new
postgresql user so my experience is limited. Cheers, Max |
