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)