NAME

       nbdkit-stats-filter - display statistics about operations

SYNOPSIS

        nbdkit --filter=stats PLUGIN statsfile=FILE
                              [statsappend=true] [statsthreshold=PERCENTILE]

DESCRIPTION

       "nbdkit-stats-filter" is a filter that displays statistics about NBD operations, such as
       the number of bytes read and written.  Statistics are written to a file once when nbdkit
       exits.

EXAMPLE OUTPUT

        # nbdkit --filter=exitlast --filter=stats memory 25G statsfile=example.txt
        # nbd-client localhost /dev/nbd1 && mkfs.ext4 /dev/nbd1 && sync &&
          nbd-client -d /dev/nbd1
        [....]
        # cat example.txt
        total: 191 ops, 21.917545 s, 25.13 GiB, 1.15 GiB/s
        read: 136 ops, 0.000230 s, 3.16 MiB, 13.43 GiB/s op, 147.83 KiB/s total
          Request size and alignment breakdown:
            12 bits: 68.4% (93 reqs, 372.00 KiB total)
                 12 bit aligned: 100.0% (93)
                 13 bit aligned:  72.0% (67)
                 14 bit aligned:  55.9% (52)
                 15 bit aligned:  48.4% (45)
                 16 bit aligned:  43.0% (40)
            14 bits: 10.3% (14 reqs, 296.00 KiB total)
                 12 bit aligned: 100.0% (14)
                 13 bit aligned:  35.7% (5)
                 19 bit aligned:  21.4% (3)
        [....]
            other sizes:  3.7% (5 reqs, 3.16 MiB total)

        write: 36 ops, 0.125460 s, 132.38 MiB, 1.03 GiB/s op, 6.04 MiB/s total
          Request size and alignment breakdown:
            12 bits: 50.0% (18 reqs, 72.00 KiB total)
                 12 bit aligned: 100.0% (18)
                 13 bit aligned:  77.8% (14)
                 27 bit aligned:  72.2% (13)
                 31 bit aligned:  66.7% (12)
                 32 bit aligned:  33.3% (6)
                 33 bit aligned:  22.2% (4)
                 34 bit aligned:  11.1% (2)
            14 bits: 30.6% (11 reqs, 224.00 KiB total)
                 12 bit aligned: 100.0% (11)
                 27 bit aligned:  90.9% (10)
            25 bits: 11.1% (4 reqs, 128.00 MiB total)
                 25 bit aligned: 100.0% (4)
                 26 bit aligned:  50.0% (2)
                 27 bit aligned:  25.0% (1)
            16 bits:  2.8% (1 reqs, 64.00 KiB total)
                 16 bit aligned: 100.0% (1)

        trim: 14 ops, 0.002687 s, 25.00 GiB, 9304.06 GiB/s op, 1.14 GiB/s total
          Request size and alignment breakdown:
            31 bits: 85.7% (12 reqs, 24.00 GiB total)
                 24 bit aligned: 100.0% (12)
            24 bits:  7.1% (1 reqs, 16.00 MiB total)

        flush: 5 ops, 0.000002 s, 0 bytes, 0 bytes/s op, 0 bytes/s total

PARAMETERS

       statsfile=FILE
           The file where we write the stats.

           This parameter is required.

       statsappend=true
           If set then we append to the file instead of replacing it.

       statsthreshold=PERCENTILE
           If non-zero, track request size and alignment distribution and print histogram.

           Requests are grouped by the number of bits that are needed to represent the request
           size (e.g. a request of size 3892 needs will be grouped with all requests of size
           2^11=2048 to 2^12-1=4095), and the number of trailing zero bits in the offset.

           Histogram output is truncated to PERCENTILE of requests. Default: 95.

FILES

       $filterdir/nbdkit-stats-filter.so
           The filter.

           Use "nbdkit --dump-config" to find the location of $filterdir.

VERSION

       "nbdkit-stats-filter" first appeared in nbdkit 1.14.

SEE ALSO

       nbdkit(1), nbdkit-filter(3), nbdkit-log-filter(1).

AUTHORS

       Richard W.M. Jones

       Nikolaus Rath

COPYRIGHT

       Copyright (C) 2019-2022 Red Hat Inc.

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