Problem:
Seeing a large perf difference when the SlaveOk() is set (DB or cursor), e.g.

cur = coll.find(query).limit(20).addOption(Bytes.QUERYOPTION_SLAVEOK);

and then performing

count = cur.itcount()

Without SlaveOk()
Inserting data :
Querying data :
Queries : 121002
Rows found : 2420040
Finished :

With SlaveOk()
Inserting data :
Querying data :
Queries : 181
Rows found : 3620
Finished :

Reproduce:

• create a two node replset
• compile attached java code
  javac -classpath mongo-2.2.jar SlaveTest.java

• run without SalveOk()
  java -cp mongo-2.2.jar SlaveTest "localhost:27000,localhost:27001" test blogs 0 1

• run with slaveOk()
  "localhost:27000,localhost:27001,localhost:27002" test blogs 2 1

Business Case:

• performance