| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "mark" <dvlhntr(at)gmail(dot)com> |
| Cc: | rod(at)iol(dot)ie, "'Mathieu De Zutter'" <mathieu(at)dezutter(dot)org>, "'Georgi Ivanov'" <georgi(dot)r(dot)ivanov(at)gmail(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Idle connections |
| Date: | 2010-10-07 05:13:50 |
| Message-ID: | 20687.1286428430@sss.pgh.pa.us |
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| Lists: | pgsql-general |
"mark" <dvlhntr(at)gmail(dot)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?
regards, tom lane
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