title: VFS Cache Hit Rate
name: cache-hit-rate.stp
version: 1.0
author: Jake Maul
keywords: io profiling vfs cache
subsystem: io
status: production
exit: user-controlled
output: timed interval (vmstat-like)
scope: system-wide
description:  The cache-hit-rate.stp script checks the bytes_read and devname fields of vfs.read.return, and uses them to determine how much data was read directly from disk vs how much was read from the Linux VFS cache.
test_check: stap -p4 cache-hit-rate.stp
test_installcheck: stap iostats.stp -c "sleep 6"