sorts with multiple batches with small collections can be slower in rc2

insert n documents query for a range of (for example) 100 documents with a batch size of 10 retrieve the first batch remove a document later in the batch exhaust the cursor The attached code is more of a stress test. It can be run against a v2.4 and v2.6 server, and will produce a .json file for each run, which can be imported/aggregated as described below: First, build with something like: c++ -I/opt/libmongoclient/include -std=c++11 -o op_bench_repro.o -c op_bench_repro.cpp c++ -I/opt/libmongoclient/include -std=c++11 -o scoped_probe.o -c scoped_probe.cpp c++ op_bench_repro.o scoped_probe.o -o op_bench_repro -rdynamic -lmongoclient -lboost_thread-mt -lboost_filesystem -lboost_program_options -lboost_system Then import the results to mongodb: echo '[' > tmp.json find . -name '*.json' |xargs cat >> tmp.json echo ']' >> tmp.json mongoimport --jsonArray --collection regression tmp.json Then aggregate: db.regression.aggregate({ $group: { _id: {ServerVersion:'$ServerVersion', TestName:'$TestName'}, Seconds: {'$sum': "$ClockSeconds"} } });