Hi, On 2020-02-01 16:17:13 -0700, Justin Lu wrote: > We are seeing very heavy LWLockTranche buffer_mapping in db recently. > > There server had 24 core, 128GB of RAM, SSD data file system, on Unbuntu > 16.04.6. > The shared_buffers was at 32GB. 1/4 of over RAM size. No issue on > checkpoints (avg time 29 min apart). > > After seeing the heavy wait, we added 64GB more RAM and increased > shared_buffers to 48GB, effective_cache_size to 90GB. But it seems there is > no impact on the buffer mapping waits at all. I suggest doing a perf profile with --call-graph dwarf, to see where this is mostly coming from. One thing I've seen causing symptoms like this before, is if there's suddenly a larger amount of table truncations, dropping, etc - dropping / truncating a table / index needs to scan all of shared buffers... Greetings, Andres Freund
