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Diffstat (limited to 'Documentation/trace/histogram.txt')
| -rw-r--r-- | Documentation/trace/histogram.txt | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/Documentation/trace/histogram.txt b/Documentation/trace/histogram.txt index df08882d091c..6e05510afc28 100644 --- a/Documentation/trace/histogram.txt +++ b/Documentation/trace/histogram.txt @@ -1671,7 +1671,16 @@ features have been added to the hist trigger support: it is in units of nanoseconds; appending '.usecs' to a common_timestamp field changes the units to microseconds. -These features are decribed in more detail in the following sections. +A note on inter-event timestamps: If common_timestamp is used in a +histogram, the trace buffer is automatically switched over to using +absolute timestamps and the "global" trace clock, in order to avoid +bogus timestamp differences with other clocks that aren't coherent +across CPUs. This can be overridden by specifying one of the other +trace clocks instead, using the "clock=XXX" hist trigger attribute, +where XXX is any of the clocks listed in the tracing/trace_clock +pseudo-file. + +These features are described in more detail in the following sections. 2.2.1 Histogram Variables ------------------------- |