Heads up: SOLR-10130, Performance issue in Solr 6.4.1

[Ere Maijala]

Hi all,

this is just a quick heads-up that we've stumbled on serious performance 
issues after upgrading to Solr 6.4.1 apparently due to the new metrics 
collection causing a major slowdown. I've filed an issue 
(https://issues.apache.org/jira/browse/SOLR-10130) about it, but decided 
to post this just so that anyone else doesn't need to encounter this 
unprepared. It seems to me that metrics would need to be explicitly 
disabled altogether in the index config to avoid the issue.

--Ere