I'm trying to diagnose which addon is causing our performance issues and something I noticed is the following:
With Post Ratings enabled:
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Without Post Ratings enabled:
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I did this 3 or 4 times, turning post ratings on/off and it's the same results every time so I'm fairly sure of the effect. The page load time is about twice as long with Post Ratings enabled but the query time isn't hugely different.
Have you got the fetch templates as files option enabled and a php opcode cache installed (apc/xcache/etc)?
I suspect there is an issue with template caching/rendering that is being masked in my testing due to that option being enabled - I'll look into it