> -----Original Message----- > From: Tom Lane [mailto:t...@sss.pgh.pa.us] > Sent: Wednesday, October 06, 2010 11:14 PM > To: mark > Cc: r...@iol.ie; 'Mathieu De Zutter'; 'Georgi Ivanov'; pgsql- > gene...@postgresql.org > Subject: Re: [GENERAL] Idle connections > > "mark" <dvlh...@gmail.com> writes: > > If you get to many persistent or otherwise idle connections you might > be > > inducing a "thundering herd" condition. Seems like on our servers we > hit a > > wall with just having a lot of persistent connections from various > apps. I > > don't really understand everything involved here but.... > > > It seems that a high number of idle connections processes will sleep > on the > > same semaphore. When this becomes run-able all the idle connections > that > > were sleeping on it become run-able at the same time. This means > hundreds > > (in our case) of idle processes do some work even though they are > idle at > > the same time. This eats all available cpu time for a few seconds > then > > everything goes back to sleep. > > What you're describing sounds a lot like the known issue with sinval > queue overflow response ... but that was fixed in 8.4. What version > is this? >
I Wanted to follow up on this, we upgraded to PG 9.0 (from 8.3) and it appears this greatly improved our average CPU load. I am not seeing the extremely large load spikes I used to. Awesome job - thank you tom and everyone else on the core team. mark > regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
