bionic (8) bitesize-perf.8.gz

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)