- 24 cpus, 64 GB memory, 1 TB hard drive
- ubuntu 15.10
- mongod 3.4.0
- standalone with: --wiredTigerCacheSizeGB 8 --wiredTigerCollectionBlockCompressor=zlib
Run 20 threads of attached repro script with:
Script inserts 139 M generic text documents ranging from 1 kB to 4 MB according to a probability distribution encoded in the script, with smaller documents being much more common. Average document size is about 60 kB. Documents typically compress about 12:1 with zlib compression in the db.
In three runs script
- hung at ~35%
- reached 50% without hanging when I terminated it
- hung at about 50%
When it hung mongod was consuming 2100% CPU, a majority of that system CPU. Per gdb stacks (attached) I think this is accounted for by 20 threads spinning in __log_slot_join and one thread spinning in __log_slot_switch_internal.