UPDATE performance degradation (6.5.1)
От | Oleg Bartunov |
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Тема | UPDATE performance degradation (6.5.1) |
Дата | |
Msg-id | Pine.GSO.3.96.SK.990727110403.29708C-100000@ra обсуждение исходный текст |
Ответы |
Re: [HACKERS] UPDATE performance degradation (6.5.1)
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Список | pgsql-hackers |
Hi, after I got DBIlogging work, I run several tests and noticed performance degradation when doing sequential updating of *one* row. I have 5 processes updated the same row. I use LOCK TABLE hits IN SHARE ROW EXCLUSIVE MODE When I run 200 requests I got about 16 req/sec, which is quite enough for my purposes. I expected the same speed if I just increase a number of requests, but it decreases. for 2000 requests I got about 10 req/sec and for 20,000 - about 2.5 req/sec ! I see no reason for such performance degradation - no way to use postgres for logging in 24*7*365 Web-site. Probably this is very specific case when several processes updates only one row, but again, I see no reason for such big degradation. Table hits itself contains only 1 row ! I'll try to elimanate httpd, perl in my test bench to test only postgres, I dont' have right now such a tool, probable someone already did this ? What tool I can use for testing concurrent update Regards, Oleg This is my home machine, Linux 2.2.10. postgres 6.5.1 Load is about 2-2.5 Typical output of ps: 11:21[om]:/usr/local/apache/logs>psg disc1036 ? S 24:17 /usr/local/pgsql/bin/postgres localhost httpd discovery LOCK1040 ? R 24:09 /usr/local/pgsql/bin/postgres localhost httpd discovery idle1042 ? S 24:02 /usr/local/pgsql/bin/postgreslocalhost httpd discovery LOCK1044 ? R 23:51 /usr/local/pgsql/bin/postgres localhost httpddiscovery idle1046 ? S 23:49 /usr/local/pgsql/bin/postgres localhost httpd discovery LOCK1048 ? S 23:47 /usr/local/pgsql/bin/postgreslocalhost httpd discovery LOCK I see only one process with SELECT, this is what I expected when use IN SHARE ROW EXCLUSIVE MODE. Right ? _____________________________________________________________ Oleg Bartunov, sci.researcher, hostmaster of AstroNet, Sternberg Astronomical Institute, Moscow University (Russia) Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/ phone: +007(095)939-16-83, +007(095)939-23-83
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