title: [MongoDB]which operations will be saved in system.profile collection when the 'profile' is 2?
body: <p>Today I want to test these two parameters "profile" and "slowms". the following is my cases:</p>
  
  <p>profile is 1 and slowms is 200</p>
  
  <ol>
  <li>>./mongod --dbpath /data/db --fork --profile 1 --slowms 200</li>
  <li>do a query and this query costed 415ms</li>
  <li>log file has the related operation message,system.profile also has the related document </li>
  <li>do a query again and this query costed 110ms </li>
  <li>log file don't have the related operation message,system.profile don't have the related document</li>
  </ol>
  
  <p>update these two parameters "profile" and "slowms"</p>
  
  <p>profile is 2 and slowms is 200</p>
  
  <ol>
  <li>>./mongod --dbpath /data/db --fork --profile 2 --slowms 200</li>
  <li>do a query and this query costed 410ms</li>
  <li>log file has the related operation message,system.profile also has the related document </li>
  <li>do a query again and this query costed 100ms </li>
  <li>log file don't have the related operation message,system.profile don't have the related document</li>
  </ol>
  
  <p>when the parameter "profile" is 2, why the log file and system.profile don't have the related information? Thanks!</p>