nbdkit-stats-filter(1)

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 Red Hat

LICENSE
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

•   Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

•   Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

•   Neither the name of Red Hat nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

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