title: Finding out what's taking up the CMA (Contiguous Memory Allocation) in Linux
body: <p>Something is definitely taking up the <code>CMA</code> buffers, but I can't figure out what.</p>
  <pre><code># cat /proc/meminfo | grep -i cma
  CmaTotal:         262144 kB
  CmaFree:            1272 kB
  </code></pre>
  <p>The system messages show little nothing:</p>
  <pre><code># dmesg | grep -i cma
  [    0.000000] cma: Reserved 256 MiB at 0x00000000c0000000
  </code></pre>
  <p>I've enabled <code>debugfs</code> for <code>cma</code>, but I have not yet figured out how to use it:</p>
  <pre><code>/sys/kernel/debug/cma/cma-reserved# ls
  alloc  base_pfn  bitmap  count  free  maxchunk  order_per_bit  used
  </code></pre>