I've got a big Drupal site running Commerce, with cloudflare caching static resources, maybe 20K users or more per day.
MariaDB caches about 500mb worth of queries, we're running freeBSD with php56 and php fastcgi. I'm using the redis PHP extension.
When I turn on redis for all the cache tables, I see the php-fcgi processes start to spike from 7% CPU up to about 35% and load goes through the roof.
Tried it a couple of times, which would minimize cache stampeding, but still I'm somewhat confused as to why redis is performing so poorly.
I've read through redis.conf and the main change I've made is not to snapshot the db to file.
I can connect with redis-cli monitor and see tons of cache data passing through.
Any ideas about what's happening here?