activerecord preloading causing after-effect performance degredation

Question

Doing a big activerecord query with a lot of peripheral objects.

Adding ".includes" (preloading) speeds it up dramatically by squashing all the N+1's.

The page then renders fast and spits this out into the logs:

Completed 200 OK in 504ms (Views: 104.2ms | ActiveRecord: 86.0ms)

However, it is then * 90 SECONDS * until the page is actually sent down to the browser (or curl; we've tested with both).

During which time the ruby process has the CPU pegged at 100%.

If we remove the ".includes" (preloading) it goes back to normal crappy performance without the minute-and-half chasm of nothingness between page render and browser delivery.

WTF does the preloading cause that after effect!?

One colleague has hypothesized a garbage collection issue; how might I test that theory?

Rails 3.2.12

Ruby 1.9.3 (p286 and p327 tested)

Answer 1

Found the problem; it was the Bullet gem (https://github.com/flyerhzm/bullet).

This gem cleverly finds and reports on N+1 queries and overzealous includes, but in the case of very large result sets it bogs down the application performance considerably.