bcc-cachetop(8)

1cachetop(8)                 System Manager's Manual                cachetop(8)
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NAME

6       cachetop  -  Statistics  for  linux page cache hit/miss ratios per pro‐
7       cesses. Uses Linux eBPF/bcc.
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SYNOPSIS

10       cachetop [interval]
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DESCRIPTION

13       This traces four kernel functions and  prints  per-processes  summaries
14       every interval seconds. This can be useful for processes workload char‐
15       acterization, and looking for patterns in operation usage over time. It
16       provides a top-like interface which by default sorts by HITS in ascend‐
17       ing order.
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19       This works by tracing kernel page cache functions using  dynamic  trac‐
20       ing,  and  will  need updating to match any changes to these functions.
21       Edit the script to customize which functions are traced.
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23       Since this uses BPF, only the root user can use this tool.
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KEYBINDINGS

26       The following  keybindings  can  be  used  to  control  the  output  of
27       cachetop.
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29       <      Use the previous column for sorting.
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31       >      Use the next column for sorting.
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33       r      Toggle sorting order (default ascending).
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35       q      Quit cachetop.
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REQUIREMENTS

38       CONFIG_BPF and bcc.
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EXAMPLES

41       Update summaries every five second:
42              # cachetop
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44       Print summaries each second:
45              # cachetop 1
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FIELDS

48       PID    Process ID of the process causing the cache activity.
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50       UID    User ID of the process causing the cache activity.
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52       HITS   Number of page cache hits.
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54       MISSES Number of page cache misses.
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56       DIRTIES
57              Number of dirty pages added to the page cache.
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59       READ_HIT%
60              Read hit percent of page cache usage.
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62       WRITE_HIT%
63              Write hit percent of page cache usage.
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65       BUFFERS_MB
66              Buffers size taken from /proc/meminfo.
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68       CACHED_MB
69              Cached   amount  of  data  in  current  page  cache  taken  from
70              /proc/meminfo.
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OVERHEAD

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

81       This is from bcc.
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83              https://github.com/iovisor/bcc
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85       Also  look  in  the bcc distribution for a companion _examples.txt file
86       containing example usage, output, and commentary for this tool.
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OS

89       Linux
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STABILITY

92       Unstable - in development.
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AUTHOR

95       Emmanuel Bretelle
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