mirrors/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2025-11-04 02:30:34 +02:00
Code Issues Projects Releases Packages Wiki Activity Actions

tracing/histogram: Document expression arithmetic and constants

Browse source 
Histogram expressions now support division, and multiplication in
addition to the already supported subtraction and addition operators.

Numeric constants can also be used in a hist trigger expressions
or assigned to a variable and used by refernce in an expression.

Link: https://lkml.kernel.org/r/20211025200852.3002369-9-kaleshsingh@google.com

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Kalesh Singh 2021-10-25 13:08:40 -07:00 committed by Steven Rostedt (VMware)
parent 722eddaa40
commit 2d2f6d4b8c
1 changed files with 14 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

14
Documentation/trace/histogram.rst
View file

@ -1763,6 +1763,20 @@ using the same key and variable from yet another event::
# echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ...' >> event3/trigger
Expressions support the use of addition, subtraction, multiplication and
division operators (+-*/).
Note that division by zero always returns -1.
Numeric constants can also be used directly in an expression::
# echo 'hist:keys=next_pid:timestamp_secs=common_timestamp/1000000 ...' >> event/trigger
or assigned to a variable and referenced in a subsequent expression::
# echo 'hist:keys=next_pid:us_per_sec=1000000 ...' >> event/trigger
# echo 'hist:keys=next_pid:timestamp_secs=common_timestamp/$us_per_sec ...' >> event/trigger
2.2.2 Synthetic Events
----------------------