On Tue, Apr 5, 2016 at 8:15 PM, Andres Freund <andres@anarazel.de> wrote: > > On 2016-04-05 17:36:49 +0300, Alexander Korotkov wrote: > > Could the reason be that we're increasing concurrency for LWLock state > > atomic variable by placing queue spinlock there? > > Don't think so, it's the same cache-line either way. > > > But I wonder why this could happen during "pgbench -S", because it doesn't > > seem to have high traffic of exclusive LWLocks. > > Yea, that confuses me too. I suspect there's some mis-aligned > datastructures somewhere. It's hard to investigate such things without > access to hardware. >
This fluctuation started appearing after commit 6150a1b0 which we have discussed in another thread [1] and a colleague of mine is working on to write a patch to try to revert it on current HEAD and then see the results.
> (FWIW, I'm working on getting pinunpin committed) >
Good to know, but I am slightly worried that it will make the problem harder to detect as it will reduce the reproducibility. I understand that we are running short of time and committing this patch is important, so we should proceed with it as this is not a problem of this patch. After this patch gets committed, we always need to revert it locally to narrow down the problem due to commit 6150a1b0.
