What's in my cache?

• The system call mincore() can be used to check if certain pages are mapped in memory or not.
• The fincore utility uses this system-call to check what part of memory a file uses.
• In combination with the lsof, we can check the entire contents of the cache:

  
       #!/bin/bash
       lsof | grep REG | awk '{print($9)}' | while read fn; do
           echo $fn `fincore $fn -justsummarize`
       done
       

• Example (very partial) output:

  
       /usr/bin/gnome-keyring-daemon page size: 4096 bytes 56 pages, 224.0 kbytes in core for 1 file; 56.00 pages, 224.0 kbytes per file.
       /lib/libnss_files-2.11.1.so page size: 4096 bytes 12 pages, 48.0 kbytes in core for 1 file; 12.00 pages, 48.0 kbytes per file.
       

• We can check this for the files used by a single process, by adding the '-p' flag to lsof.

Originally written by guy keren