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Diffstat (limited to 'cddl/contrib/dtracetoolkit/Notes/ALLoncpu_notes.txt')
| -rw-r--r-- | cddl/contrib/dtracetoolkit/Notes/ALLoncpu_notes.txt | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/cddl/contrib/dtracetoolkit/Notes/ALLoncpu_notes.txt b/cddl/contrib/dtracetoolkit/Notes/ALLoncpu_notes.txt new file mode 100644 index 000000000000..41aead027bc9 --- /dev/null +++ b/cddl/contrib/dtracetoolkit/Notes/ALLoncpu_notes.txt @@ -0,0 +1,42 @@ +************************************************************************** +* The following are notes for all scripts that measure on-CPU times. +* +* $Id: ALLoncpu_notes.txt 58 2007-10-01 13:36:29Z brendan $ +* +* COPYRIGHT: Copyright (c) 2007 Brendan Gregg. +************************************************************************** + + +* What is "on-CPU" time? + +This is the time that a thread spent running on a CPU. It does not include +time spent off-CPU time such as sleeping for I/O or waiting for scheduling. + +On-CPU times are useful for showing who is causing the CPUs to be busy, +since they measure how much CPU time has been consumed by that thread. + +On-CPU times are also less susceptible to system "noise" than elapsed times, +since much of the noise will be filtered out. DTrace itself also tries +to subtract the small overheads of DTrace from the on-CPU time, to improve +the accuracy of this time. + +See Notes/ALLelapsed_notes.txt for a description of a different time +measurement, "elapsed" time. + + +* How is "on-CPU" time measured? + +In DTrace, the following template provides on-CPU time as "this->oncpu", + + <start-probe> + { + self->vstart = vtimestamp; + } + + <end-probe> + { + this->oncpu = vtimestamp - self->vstart; + self->vstart = 0; + ... + } + |