title: Is MongoDB somehow limited to a single core?
body: <p>Perhaps I have misconfigured MongoDB somehow, but even under heavy load I don't see it using more than one core. For example, top is currently showing:</p>
  
  <pre><code>Tasks: 145 total,   1 running, 144 sleeping,   0 stopped,   0 zombie
  Cpu0  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
  Cpu1  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
  Cpu2  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
  Cpu3  :100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
  Mem:  41182768k total, 40987476k used,   195292k free,   109956k buffers
  Swap:  2097144k total,  1740288k used,   356856k free, 28437928k cached
  
    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                         
  16297 mongod    15   0  521g  18g  18g S 99.8 47.2   2929:32 mongod                                                                           
      1 root      15   0 10372  256  224 S  0.0  0.0   0:03.39 init      
  </code></pre>
  
  <p>Is there something I can do to get Mongo to use the other cores more effectively? If it's relevant, I currently have a big M/R running which seems to have put a lot of read queries in "waiting" mode.</p>