On Wed, Aug 28, 2019 at 3:05 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > I'd vote for back-patching to 10. Even if there is in fact no deadlock > hazard, you've clearly demonstrated a significant performance hit that > we're taking for basically no reason.
Done. The second symptom reported in my first email looked like evidence of high levels of spinlock backoff, which I guess might have been coming from TransactionIdLimitedForOldSnapshots()'s hammering of oldSnapshotControl->mutex_threshold and oldSnapshotControl->mutex_threshold, when running heap_page_prune_opt()-heavy workloads like the one generated by test-indexscan.sql (from my earlier message) from many backends at the same time on a large system. That's just an observation I'm leaving here, I'm not planning to chase that any further for now. -- Thomas Munro https://enterprisedb.com
