path: root/Documentation
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authorLinus Torvalds <torvalds@linux-foundation.org>2018-06-24 06:23:28 +0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-24 06:23:28 +0800
commit81f9c4e4177d31ced6f52a89bb70e93bfb77ca03 (patch)
tree2c9130e553e1321e5533a5c04a55442964390bdb /Documentation
parent5e2204832b20ef9db859dd6a2e955ac3e33eef27 (diff)
parented7d40bc67b8353c677b38c6cdddcdc310c0f452 (diff)
Merge tag 'trace-v4.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fixes from Steven Rostedt: "This contains a few fixes and a clean up. - a bad merge caused an "endif" to go in the wrong place in scripts/Makefile.build - softirq tracing fix for tracing that corrupts lockdep and causes a false splat - histogram documentation typo fixes - fix a bad memory reference when passing in no filter to the filter code - simplify code by using the swap macro instead of open coding the swap" * tag 'trace-v4.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Fix SKIP_STACK_VALIDATION=1 build due to bad merge with -mrecord-mcount tracing: Fix some errors in histogram documentation tracing: Use swap macro in update_max_tr softirq: Reorder trace_softirqs_on to prevent lockdep splat tracing: Check for no filter when processing event filters
Diffstat (limited to 'Documentation')
1 files changed, 12 insertions, 11 deletions
diff --git a/Documentation/trace/histogram.txt b/Documentation/trace/histogram.txt
index e73bcf9cb5f3..7ffea6aa22e3 100644
--- a/Documentation/trace/histogram.txt
+++ b/Documentation/trace/histogram.txt
@@ -1729,35 +1729,35 @@ If a variable isn't a key variable or prefixed with 'vals=', the
associated event field will be saved in a variable but won't be summed
as a value:
- # echo 'hist:keys=next_pid:ts1=common_timestamp ... >> event/trigger
+ # echo 'hist:keys=next_pid:ts1=common_timestamp ...' >> event/trigger
Multiple variables can be assigned at the same time. The below would
result in both ts0 and b being created as variables, with both
common_timestamp and field1 additionally being summed as values:
- # echo 'hist:keys=pid:vals=$ts0,$b:ts0=common_timestamp,b=field1 ... >> \
+ # echo 'hist:keys=pid:vals=$ts0,$b:ts0=common_timestamp,b=field1 ...' >> \
Note that variable assignments can appear either preceding or
following their use. The command below behaves identically to the
command above:
- # echo 'hist:keys=pid:ts0=common_timestamp,b=field1:vals=$ts0,$b ... >> \
+ # echo 'hist:keys=pid:ts0=common_timestamp,b=field1:vals=$ts0,$b ...' >> \
Any number of variables not bound to a 'vals=' prefix can also be
assigned by simply separating them with colons. Below is the same
thing but without the values being summed in the histogram:
- # echo 'hist:keys=pid:ts0=common_timestamp:b=field1 ... >> event/trigger
+ # echo 'hist:keys=pid:ts0=common_timestamp:b=field1 ...' >> event/trigger
Variables set as above can be referenced and used in expressions on
another event.
For example, here's how a latency can be calculated:
- # echo 'hist:keys=pid,prio:ts0=common_timestamp ... >> event1/trigger
- # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ... >> event2/trigger
+ # echo 'hist:keys=pid,prio:ts0=common_timestamp ...' >> event1/trigger
+ # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...' >> event2/trigger
In the first line above, the event's timetamp is saved into the
variable ts0. In the next line, ts0 is subtracted from the second
@@ -1766,7 +1766,7 @@ yet another variable, 'wakeup_lat'. The hist trigger below in turn
makes use of the wakeup_lat variable to compute a combined latency
using the same key and variable from yet another event:
- # echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ... >> event3/trigger
+ # echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ...' >> event3/trigger
2.2.2 Synthetic Events
@@ -1807,10 +1807,11 @@ the command that defined it with a '!':
At this point, there isn't yet an actual 'wakeup_latency' event
instantiated in the event subsytem - for this to happen, a 'hist
trigger action' needs to be instantiated and bound to actual fields
-and variables defined on other events (see Section 6.3.3 below).
+and variables defined on other events (see Section 2.2.3 below on
+how that is done using hist trigger 'onmatch' action). Once that is
+done, the 'wakeup_latency' synthetic event instance is created.
-Once that is done, an event instance is created, and a histogram can
-be defined using it:
+A histogram can now be defined for the new synthetic event:
# echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \
@@ -1960,7 +1961,7 @@ hist trigger specification.
back to that pid, the timestamp difference is calculated. If the
resulting latency, stored in wakeup_lat, exceeds the current
maximum latency, the values specified in the save() fields are
- recoreded:
+ recorded:
# echo 'hist:keys=pid:ts0=common_timestamp.usecs \
if comm=="cyclictest"' >> \