Kris Kennaway <[EMAIL PROTECTED]> writes: > On Tue, Apr 10, 2007 at 05:36:17PM -0400, Tom Lane wrote: >> Anyway I'd be interested to know what the test case is, and which PG >> version you were testing.
> I used 8.2 (and some older version when I first noticed it a year ago) > and either sysbench or supersmack will show it - presumably anything > that makes simultaneous queries. Just instrument sleepq_broadcast() > to e.g. log a KTR event when it wakes more than 1 process and you'll > see it happening. Sorry, I'm not much of a BSD kernel hacker ... but sleepq_broadcast seems a rather generic name. Is that called *only* from semop? I'm wondering if you are seeing simultaneous wakeup from some other cause --- sleep timeout being the obvious possibility. We are aware of behaviors (search the PG lists for "context swap storm") where a number of backends will all fail to get a spinlock and do short usleep or select-timeout waits. In this situation they'd all wake up at the next scheduler clock tick ... regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match