On Thu, 2005-12-08 at 09:44 -0500, Tom Lane wrote: > Simon Riggs <[EMAIL PROTECTED]> writes: > > The output you gave wasn't anything I recognize in the code. Assuming > > its not already there, please can you share code you are using to find > > the evidence, even if its just privately in some form? > > See below. Also, the message I previously mentioned shows a different > tack on the same theme: > http://archives.postgresql.org/pgsql-patches/2003-12/msg00365.php > although in the light of later events I think that keeping the counts > in shared memory like that is a bad idea --- too likely to skew the > results.
Looks good, thanks. Like the shmem_exit solution. I'll use this in any testing, to allow easier discussion of results and encourage all other testers to do the same. > > You're looking at the number of spins to acquire each lock? > > Number of semop waits. I wonder whether that is the thing to measure. That measure doesn't show how long each waiter waited. I would also want to see: - queue length at wait time - any variability over time I was thinking of looking at the histogram of wait queue length frequency for the highly contested locks. > > Manfred's earlier patch provides very clear output for observing > > contention, including full summaries. Could we commit that, so we can > > all use this for analysis? Updated with the wait info. > > What patch would that be? Sorry, thought Manfred had written the earlier patch. Best Regards, Simon Riggs ---------------------------(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