Background:

We just moved our production system from MMAP to WiredTiger, and are generally seeing extremely poor performance.

• Very high CPU usage on low-medium loads (often all CPU cores pegged at 100%)
• Long delays in read queries (presumably because CPU-bound performance)
• Individual CPU cores pegged at 100% randomly, even when there is no activity according to db.currentOp()

I thought that maybe this was something specific to our workload that might be causing problems. I was going to change some of the read-intensive collections from snappy compression, to no compression, to see if that improved things at all, however today I came across the mongodump issue, which is a show stopper for us (as we use mongodump for live backups).

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In a nutshell: When mongodump is running, all application queries to the db seem to be blocked.

(It's also worth noting that mongodump takes a lot longer to run on WT, which though not a major problem, does compound the issue).