Provided by: perf-tools-unstable_0.0.1~20150130+git85414b0-1_all bug

NAME

       bitesize - show disk I/O size as a histogram. Uses Linux perf_events.

SYNOPSIS

       bitesize [-h] [-b buckets] [seconds]

DESCRIPTION

       This  can  be  used  to  characterize  the distribution of block device
       (disk) I/O sizes. To  study  block  device  I/O  in  more  detail,  see
       iosnoop(8).

       This uses multiple counting tracepoints with different filters, one for
       each histogram bucket. While this is summarized in-kernel, the  use  of
       multiple  tracepoints  does  add  addiitonal  overhead,  which  is more
       evident if you add more buckets. In the future this functionality  will
       be  available  in  an efficient way in the kernel, and this tool can be
       rewritten.

REQUIREMENTS

       Linux perf_events: add linux-tools-common, run  "perf",  then  add  any
       additional    packages    it   requests.   This   also   requires   the
       block:block_rq_issue tracepoint, which should already be  available  in
       recent kernels.

OPTIONS

       -h     Usage message.

       -b buckets
              Specify  a  list  of bucket points for the histogram as a string
              (eg, "10 500 1000"). The  histogram  will  include  buckets  for
              less-than the minimum, and greater-than-or-equal-to the maximum.
              If  a  single  value  is  specified,  two  statistics  only  are
              gathered:  for  less-than and for greater-than-or-equal-to.  The
              overhead  is  relative  to  the  number  of  buckets,  so   only
              specifying a single value costs the lowest overhead.

       seconds
              Number  of  seconds  to trace. If not specified, this runs until
              Ctrl-C.

EXAMPLES

       Trace read() syscalls until Ctrl-C, and  show  histogram  of  requested
       size:
              # bitesize syscalls:sys_enter_read count

FIELDS

       Kbytes Kbyte range of the histogram bucket.

       I/O    Number of I/O that occurred in this range while tracing.

       Distribution
              ASCII histogram representation of the I/O column.

OVERHEAD

       While  the counts are performed in-kernel, there is one tracepoint used
       per histogram bucket, so the overheads are higher than usual  (relative
       to  the  number of buckets) than function counting using perf stat. The
       lowest overhead is  when  -b  is  used  to  specify  one  bucket  only,
       bifurcating statistics.

SOURCE

       This is from the perf-tools collection.

              https://github.com/brendangregg/perf-tools

       Also  look  under  the  examples  directory  for a text file containing
       example usage, output, and commentary for this tool.

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       iosnoop(8), iolatency(8), iostat(1)