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Diffstat (limited to 'Notes/ALLexclusive_notes.txt')
| -rw-r--r-- | Notes/ALLexclusive_notes.txt | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/Notes/ALLexclusive_notes.txt b/Notes/ALLexclusive_notes.txt new file mode 100644 index 000000000000..7aeb9ffde84c --- /dev/null +++ b/Notes/ALLexclusive_notes.txt @@ -0,0 +1,78 @@ +************************************************************************** +* Notes for all scripts that print exclusive function times (or method, +* or subroutine). +* +* $Id: ALLexclusive_notes.txt 45 2007-09-17 08:54:56Z brendan $ +* +* COPYRIGHT: Copyright (c) 2007 Brendan Gregg. +************************************************************************** + + +* What is "exclusive" function time? + +This is the time of function execution, from when the function begins to +when it completes, excluding the time spent executing any child function. + +Exclusive function time can be calculated like this, + + exclusive function time = time(function end) - time(function start) - + time(total child exclusive time) + +To do this, the DTrace script needs to keep trace of child function execution +time, so that it can be subtracted from the parent execution time. + +Consider this Bourne shell program, + 1 #!./sh + 2 + 3 func_c() + 4 { + 5 echo "Function C" + 6 sleep 1 + 7 } + 8 + 9 func_b() + 10 { + 11 echo "Function B" + 12 sleep 1 + 13 func_c + 14 } + 15 + 16 func_a() + 17 { + 18 echo "Function A" + 19 sleep 1 + 20 func_b + 21 } + 22 + 23 func_a + +func_a() calls func_b() which calls func_c(). Tracing the flow using +sh_flowtime.d shows, + +# ./sh_flowtime.d | cat -n + 1 C TIME(us) FILE DELTA(us) -- NAME + 2 0 3052991099265 func_abc.sh 2 -> func_a + 3 0 3052991099324 func_abc.sh 59 > echo + 4 0 3052992111638 func_abc.sh 1012314 | sleep + 5 0 3052992111678 func_abc.sh 39 -> func_b + 6 0 3052992111729 func_abc.sh 51 > echo + 7 0 3052993121633 func_abc.sh 1009903 | sleep + 8 0 3052993121693 func_abc.sh 60 -> func_c + 9 0 3052993121745 func_abc.sh 52 > echo + 10 0 3052994131634 func_abc.sh 1009888 | sleep + 11 0 3052994131685 func_abc.sh 50 <- func_c + 12 0 3052994131699 func_abc.sh 14 <- func_b + 13 0 3052994131707 func_abc.sh 7 <- func_a + +the output of DTrace was piped through "cat -n" to enumerate the lines. + +Exclusive function time for func_a() in the above output would be the +time from line 2 to line 13 minus the time from line 5 to 12 to subtract +the time spent in both func_b() and func_c(). Or, you could say that +exclusive time for func_a() is the time from lines 2 to 4. + +Looking back at the code, exclusive time for func_a() is the time spent +in code lines 18 and 19 (and not line 20). + +See Notes/ALLinclusive_notes.txt for details on "inclusive" function time. + |