On Tue, Apr 10, 2007 at 05:36:17PM -0400, Tom Lane wrote: > Kris Kennaway <[EMAIL PROTECTED]> writes: > > I have not studied the exact code path, but there are indeed multiple > > wakeups happening from the semaphore code (as many as the number of > > active postgresql processes). It is easy to instrument > > sleepq_broadcast() and log them when they happen. > > There are certainly cases where Postgres will wake up a number of > processes in quick succession, but that should happen from a separate > semop() kernel call, on a different semaphore, for each such process. > If there's really multiple processes being released by the same semop() > then there's a bug we need to look into (or maybe it's a kernel bug?). > 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. Kris
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