system_cmds/iosim.tproj/iosim.1

   1 .\" Copyright (c) 2013, Apple Inc.  All rights reserved.
   2 .\"
   3 .Dd Oct 9, 2013
   4 .Dt IOSIM 1
   5 .Sh NAME
   6 .Nm iosim
   7 .Nd A performance tool to simulate I/O workloads.
   8 .Sh SYNOPSIS
   9 .Pp
  10 .Nm iosim
  11 .Ar -c <number>
  12 Burst Count. No. of I/Os performed in an I/O burst.
  13 Default Value: 10
  14 Valid Range: [0, INT_MAX]
  15 .Pp
  16 .Nm iosim
  17 .Ar -i <msecs>
  18 Inter Burst Duration. Amount of time each thread sleeps between bursts (-1 indicates random durations between 0-100 msecs)
  19 Default Value: 0
  20 Valid Range: [-1, INT_MAX]
  21 .Pp
  22 .Nm iosim
  23 .Ar -d <msecs>
  24 Inter I/O delay. Amount of time thread sleeps between issuing I/Os
  25 Default Value: 0
  26 Valid Range: [0, INT_MAX]
  27 .Pp
  28 .Nm iosim
  29 .Ar -t <number>
  30 Thread count
  31 Default Value: 1
  32 Valid Range: [0, 1000]
  33 .Pp
  34 .Nm iosim
  35 .Ar -f <number>
  36 Workload Type (0/1/2 : Read-Only/Write-Only/Mixed RW)
  37 Default Value: 0
  38 Valid Range: [0, 2]
  39 .Pp
  40 .Nm iosim
  41 .Ar -m <number>
  42 I/O Pattern (0/1 : Sequential/Random)
  43 Default Value: 0
  44 Valid Range: [0, 1]
  45 .Pp
  46 .Nm iosim
  47 .Ar -j <bytes>
  48 Size of I/O in bytes
  49 Default Value: 4096
  50 Valid Range: [0, INT_MAX]
  51 .Pp
  52 .Nm iosim
  53 .Ar -s <msecs>
  54 Frequency of sync() calls
  55 Default Value: 5000
  56 Valid Range: [0, INT_MAX]
  57 .Pp
  58 .Nm iosim
  59 .Ar -l <number>
  60 I/O Tier (0/1/2/3)
  61 Default Value: 0
  62 Valid Range: [0, 3]
  63 .Pp
  64 .Nm iosim
  65 .Ar -z <number>
  66 Size of the file created specified in pages (Only used when the file is being created by the tool)
  67 Default Value: 1 GB
  68 Valid Range: [0, INT_MAX]
  69 .Pp
  70 .Nm iosim
  71 .Ar -x <secs>
  72 Test duration (0 indicates that the tool would wait for a Ctrl-C)
  73 Default Value: 0
  74 Valid Range: [0, INT_MAX]
  75 .Pp
  76 .Nm iosim
  77 .Ar -a number
  78 I/O Caching behavior (0/1 : Non-cached/Cached)
  79 Default Value: 0
  80 Valid Range: [0, 1]
  81 .Pp
  82 .Nm iosim
  83 .Ar -n <filename>
  84 Filename for I/Os (If this option is not specified, the tool would create files on its own)
  85 Valid Range: Valid filename
  86 .Sh DESCRIPTION
  87 The
  88 .Nm iosim
  89 tool allows simulating workloads for I/O performance evaluation. The tool spawns 'n' threads which issue non-cached I/Os. If specified, it also creates a sync thread which issues system wide sync() calls to flush data and metadata to disk (emulates launchd behavior). The I/Os are issued at the specified I/O tier and the tool reports latency and throughput numbers.
  90 .P
  91 .nf
  92 Following is an explanation of the results:
  93 Avg. Latency : Avg. latency experienced by the I/Os.
  94 Low Latency Histogram: Frequency distribution of I/O latency for low latency I/Os.
  95 Latency Histogram: Frequency distribution of I/O latency.
  96 Burst Avg. Latency Histogram: Frequency distribution of burst avg. latency.
  97 Throughput timeline: Time windowed throughput distrbution.
  98 .fi
  99 .Sh SEE ALSO
 100 .Xr fs_usage 1