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                              op: <Id.Redir_Great '>'>
                              loc: (redir_loc.Fd fd:1)
                              arg: {<snapshot>}
                            )
                          ]
                          do_fork: T
                        )
                        (command.Simple
                          blame_tok: <echo>
                          more_env: []
                          words: [{<echo>}]
                          redirects: [
                            (Redir
                              op: <Id.Redir_Great '>'>
                              loc: (redir_loc.Fd fd:1)
                              arg: {<trace>}
                            )
                          ]
                          do_fork: T
                        )
                        (command.Simple
                          blame_tok: <cat>
                          more_env: []
                          words: [{<cat>} {<snapshot>}]
                          redirects: []
                          do_fork: T
                        )
                      ]
                      spids: [1060 1071]
                    )
                  ]
                  else_kw: <Id.KW_Else else>
                  else_action: [
                    (command.Simple
                      blame_tok: <cat>
                      more_env: []
                      words: [{<cat>} {<trace>}]
                      redirects: []
                      do_fork: T
                    )
                    (command.Simple
                      blame_tok: <echo>
                      more_env: []
                      words: [{<echo>}]
                      redirects: [(Redir op:<Id.Redir_Great '>'> loc:(redir_loc.Fd fd:1) arg:{<trace>})]
                      do_fork: T
                    )
                  ]
                  fi_kw: <Id.KW_Fi fi>
                  redirects: []
                )
                (command.AndOr
                  children: [
                    (command.DParen
                      left: <Id.Op_DLeftParen _>
                      child: ($ Id.Lit_ArithVarLike opt_timestamp)
                      right: <Id.Op_DRightParen _>
                      redirects: []
                    )
                    (command.Simple
                      blame_tok: <printf>
                      more_env: []
                      words: [
                        {<printf>}
                        {(DQ <'time %(%H:%M:%S)T:'> <Id.Lit_BadBackslash '\\'> <n>)}
                        {<-1>}
                      ]
                      redirects: []
                      do_fork: T
                    )
                  ]
                  ops: [<Id.Op_DAmp _>]
                )
                (command.Simple
                  blame_tok: <echo>
                  more_env: []
                  words: [{<echo>} {(DQ <tick>)}]
                  redirects: []
                  do_fork: T
                )
              ]
              right: <Id.KW_Done done>
            )
          redirects: []
        )
        (command.Simple
          blame_tok: <Id.VSub_DollarName '$awk'>
          more_env: []
          words: [
            {($ Id.VSub_DollarName awk)}
            {<-v>}
            {<Id.Lit_VarLike 'o='> ($ Id.VSub_DollarName offset)}
            {<-v>}
            {<Id.Lit_VarLike 'opt_timestamp='> ($ Id.VSub_DollarName opt_timestamp)}
            {<-v>}
            {<Id.Lit_VarLike 'b_start='> ($ Id.VSub_DollarName b_start)}
            {
              (SQ <'\n'> <'\tfunction star(sval, smax, swidth) {\n'> <'\t\tstars = ""\n'> 
                <'\t\tif (smax == 0) return ""\n'> <'\t\tfor (si = 0; si < (swidth * sval / smax); si++) {\n'> <'\t\t\tstars = stars "#"\n'> <'\t\t}\n'> 
                <'\t\treturn stars\n'> <'\t}\n'> <'\n'> <'\tBEGIN { max_i = 0 }\n'> <'\n'> <'\t# common fields\n'> <'\t$1 != "#" {\n'> 
                <'\t\ttime = $(3+o); sub(":", "", time)\n'> <'\t\tdev = $(5+o)\n'> <'\t}\n'> <'\n'> <'\t# block I/O request\n'> <'\t$1 != "#" && $0 ~ b_start {\n'> 
                <'\t\t#\n'> <'\t\t# example: (fields1..4+o) 202,1 W 0 () 12862264 + 8 [tar]\n'> 
                <'\t\t# The cmd field "()" might contain multiple words (hex),\n'> <'\t\t# hence stepping from the right (NF-3).\n'> <'\t\t#\n'> <'\t\tloc = $(NF-3)\n'> 
                <'\t\tstarts[dev, loc] = time\n'> <'\t\tnext\n'> <'\t}\n'> <'\n'> <'\t# block I/O completion\n'> <'\t$1 != "#" && $0 ~ /rq_complete/ {\n'> 
                <'\t\t#\n'> <'\t\t# example: (fields1..4+o) 202,1 W () 12862256 + 8 [0]\n'> <'\t\t#\n'> <'\t\tdir = $(6+o)\n'> 
                <'\t\tloc = $(NF-3)\n'> <'\n'> <'\t\tif (starts[dev, loc] > 0) {\n'> <'\t\t\tlatency_ms = 1000 * (time - starts[dev, loc])\n'> 
                <'\t\t\ti = 0\n'> <'\t\t\tfor (ms = 1; latency_ms > ms; ms *= 2) { i++ }\n'> <'\t\t\thist[i]++\n'> 
                <'\t\t\tif (i > max_i)\n'> <'\t\t\t\tmax_i = i\n'> <'\t\t\tdelete starts[dev, loc]\n'> <'\t\t}\n'> <'\t\tnext\n'> <'\t}\n'> <'\n'> 
                <'\t# timestamp\n'> <'\t$1 == "time" {\n'> <'\t\tlasttime = $2\n'> <'\t}\n'> <'\n'> <'\t# print summary\n'> 
                <'\t$1 == "tick" {\n'> <'\t\tprint ""\n'> <'\t\tif (opt_timestamp)\n'> <'\t\t\tprint lasttime\n'> <'\n'> 
                <'\t\t# find max value\n'> <'\t\tmax_v = 0\n'> <'\t\tfor (i = 0; i <= max_i; i++) {\n'> <'\t\t\tif (hist[i] > max_v)\n'> 
                <'\t\t\t\tmax_v = hist[i]\n'> <'\t\t}\n'> <'\n'> <'\t\t# print histogram\n'> 
                <'\t\tprintf "%8s .. %-8s: %-8s |%-38s|\\n", ">=(ms)", "<(ms)",\n'> <'\t\t    "I/O", "Distribution"\n'> <'\t\tms = 1\n'> <'\t\tfrom = 0\n'> 
                <'\t\tfor (i = 0; i <= max_i; i++) {\n'> <'\t\t\tprintf "%8d -> %-8d: %-8d |%-38s|\\n", from, ms,\n'> 
                <'\t\t\t    hist[i], star(hist[i], max_v, 38)\n'> <'\t\t\tfrom = ms\n'> <'\t\t\tms *= 2\n'> <'\t\t}\n'> <'\t\tfflush()\n'> <'\t\tdelete hist\n'> 
                <'\t\tdelete starts\t# invalid if events missed between snapshots\n'> <'\t\tmax_i = 0\n'> <'\t}\n'> <'\n'> 
                <'\t$0 ~ /LOST.*EVENTS/ { print "WARNING: " $0 > "/dev/stderr" }\n'>
              )
            }
          ]
          redirects: []
          do_fork: T
        )
      ]
      ops: [<Id.Op_Pipe _>]
    )
    (command.Simple blame_tok:<end> more_env:[] words:[{<end>}] redirects:[] do_fork:T)
  ]
)