Discover which parts of a file are cached by the OS.
This command uses the mincore() system call on linux to grab a mapping of cached pages. Currently this done with a single mincore() call and requires 1-byte for each 4KiB page. For very large files, this may require several MiBs or more of memory. For a 1TB file this is 256MiB, for instance.
Usage: dbsake fincore [OPTIONS] [PATHS]... Report cached pages for a file. Options: -v, --verbose -?, --help Show this message and exit.
# dbsake fincore /var/lib/mysql/ibdata1 /var/lib/mysql/ibdata1: total_pages=6656 cached=0 percent=0.00 # cat /var/lib/mysql/ibdata1 > /dev/null # dbsake fincore /var/lib/mysql/ibdata1 /var/lib/mysql/ibdata1: total_pages=6656 cached=6656 percent=100.00