# ./cachetop -h usage: cachetop.py [-h] [interval] show Linux page cache hit/miss statistics including read and write hit % per processes in a UI like top. positional arguments: interval Interval between probes. optional arguments: -h, --help show this help message and exit examples: ./cachetop # run with default option of 5 seconds delay ./cachetop 1 # print every second hit/miss stats # ./cachetop 5 13:01:01 Buffers MB: 76 / Cached MB: 114 / Sort: HITS / Order: ascending PID UID CMD HITS MISSES DIRTIES READ_HIT% WRITE_HIT% 1 root systemd 2 0 0 100.0% 0.0% 680 root vminfo 3 4 2 14.3% 42.9% 567 syslog rs:main Q:Reg 10 4 2 57.1% 21.4% 986 root kworker/u2:2 10 2457 4 0.2% 99.5% 988 root kworker/u2:2 10 9 4 31.6% 36.8% 877 vagrant systemd 18 4 2 72.7% 13.6% 983 root python 148 3 143 3.3% 1.3% 981 root strace 419 3 143 65.4% 0.5% 544 messageb dbus-daemon 455 371 454 0.1% 0.4% 243 root jbd2/dm-0-8 457 371 454 0.4% 0.4% 985 root (mount) 560 2457 4 18.4% 81.4% 987 root systemd-udevd 566 9 4 97.7% 1.2% 988 root systemd-cgroups 569 9 4 97.8% 1.2% 986 root modprobe 578 9 4 97.8% 1.2% 287 root systemd-journal 598 371 454 14.9% 0.3% 985 root mount 692 2457 4 21.8% 78.0% 984 vagrant find 9529 2457 4 79.5% 20.5% Above shows the run of `find /` on a newly booted system. Command used to generate the activity # find / Below shows the hit rate increases as we run find a second time and it gets it its pages from the cache. # ./cachetop.py 13:01:01 Buffers MB: 76 / Cached MB: 115 / Sort: HITS / Order: ascending PID UID CMD HITS MISSES DIRTIES READ_HIT% WRITE_HIT% 544 messageb dbus-daemon 2 2 1 25.0% 50.0% 680 root vminfo 2 2 1 25.0% 50.0% 243 root jbd2/dm-0-8 3 2 1 40.0% 40.0% 1068 root python 5 0 0 100.0% 0.0% 1071 vagrant bash 350 0 0 100.0% 0.0% 1071 vagrant find 12959 0 0 100.0% 0.0% Below shows that the dirty pages increases as a file of 80M is created running # dd if=/dev/urandom of=/tmp/c bs=8192 count=10000 # ./cachetop.py 10 13:01:01 Buffers MB: 77 / Cached MB: 193 / Sort: HITS / Order: ascending PID UID CMD HITS MISSES DIRTIES READ_HIT% WRITE_HIT% 544 messageb dbus-daemon 9 10 7 10.5% 15.8% 680 root vminfo 9 10 7 10.5% 15.8% 1109 root python 22 0 0 100.0% 0.0% 243 root jbd2/dm-0-8 25 10 7 51.4% 8.6% 1070 root kworker/u2:2 85 0 0 100.0% 0.0% 1110 vagrant bash 366 0 0 100.0% 0.0% 1110 vagrant dd 42183 40000 20000 27.0% 24.3% The file copied into page cache was named /tmp/c with a size of 81920000 (81920000/4096) = 20000