NAME

       cachetop - Statistics for linux page cache hit/miss ratios per processes. Uses Linux eBPF/bcc.

SYNOPSIS

       cachetop [-p PID] [interval]

DESCRIPTION

       This  traces four kernel functions and prints per-processes summaries every interval seconds. This can be
       useful for processes workload characterization, and looking for patterns in operation usage over time. It
       provides a top-like interface which by default sorts by HITS in ascending order.

       This  works by tracing kernel page cache functions using dynamic tracing, and will need updating to match
       any changes to these functions. Edit the script to customize which functions are traced.

       Since this uses BPF, only the root user can use this tool.

OPTIONS

       -p PID Trace this PID only.

KEYBINDINGS

       The following keybindings can be used to control the output of cachetop.

       <      Use the previous column for sorting.

       >      Use the next column for sorting.

       r      Toggle sorting order (default ascending).

       q      Quit cachetop.

REQUIREMENTS

       CONFIG_BPF and bcc.

EXAMPLES

       Update summaries every five second:
              # cachetop

       Print summaries each second:
              # cachetop 1

FIELDS

       PID    Process ID of the process causing the cache activity.

       UID    User ID of the process causing the cache activity.

       CMD    Name of the process.

       HITS   Number of page cache hits.

       MISSES Number of page cache misses.

       DIRTIES
              Number of dirty pages added to the page cache.

       READ_HIT%
              Read hit percent of page cache usage.

       WRITE_HIT%
              Write hit percent of page cache usage.

       BUFFERS_MB
              Buffers size taken from /proc/meminfo.

       CACHED_MB
              Cached amount of data in current page cache taken from /proc/meminfo.

OVERHEAD

       This traces various kernel page cache functions and maintains in-kernel counts, which are  asynchronously
       copied  to  user-space.  While  the  rate  of operations can be very high (>1G/sec) we can have up to 34%
       overhead, this is still a relatively efficient way to trace these events, and so the overhead is expected
       to be small for normal workloads.  Measure in a test environment.

SOURCE

       This is from bcc.

              https://github.com/iovisor/bcc

       Also  look  in  the bcc distribution for a companion _examples.txt file containing example usage, output,
       and commentary for this tool.

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Emmanuel Bretelle, Rocky Xing

SEE ALSO

       cachestat (8)