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-rw-r--r--Documentation/trace/histogram.rst92
-rw-r--r--kernel/trace/trace.c1
2 files changed, 87 insertions, 6 deletions
diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst
index f99be8062bc8..4e650671f245 100644
--- a/Documentation/trace/histogram.rst
+++ b/Documentation/trace/histogram.rst
@@ -77,6 +77,7 @@ Documentation written by Tom Zanussi
.syscall display a syscall id as a system call name
.execname display a common_pid as a program name
.log2 display log2 value rather than raw number
+ .buckets=size display grouping of values rather than raw number
.usecs display a common_timestamp in microseconds
=========== ==========================================
@@ -228,7 +229,7 @@ Extended error information
that lists the total number of bytes requested for each function in
the kernel that made one or more calls to kmalloc::
- # echo 'hist:key=call_site:val=bytes_req' > \
+ # echo 'hist:key=call_site:val=bytes_req.buckets=32' > \
/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
This tells the tracing system to create a 'hist' trigger using the
@@ -1823,20 +1824,99 @@ 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.
-A histogram can now be defined for the new synthetic event::
-
- # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \
- /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
-
The new event is created under the tracing/events/synthetic/ directory
and looks and behaves just like any other event::
# ls /sys/kernel/debug/tracing/events/synthetic/wakeup_latency
enable filter format hist id trigger
+A histogram can now be defined for the new synthetic event::
+
+ # echo 'hist:keys=pid,prio,lat.log2:sort=lat' >> \
+ /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
+
+The above shows the latency "lat" in a power of 2 grouping.
+
Like any other event, once a histogram is enabled for the event, the
output can be displayed by reading the event's 'hist' file.
+ # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/hist
+
+ # event histogram
+ #
+ # trigger info: hist:keys=pid,prio,lat.log2:vals=hitcount:sort=lat.log2:size=2048 [active]
+ #
+
+ { pid: 2035, prio: 9, lat: ~ 2^2 } hitcount: 43
+ { pid: 2034, prio: 9, lat: ~ 2^2 } hitcount: 60
+ { pid: 2029, prio: 9, lat: ~ 2^2 } hitcount: 965
+ { pid: 2034, prio: 120, lat: ~ 2^2 } hitcount: 9
+ { pid: 2033, prio: 120, lat: ~ 2^2 } hitcount: 5
+ { pid: 2030, prio: 9, lat: ~ 2^2 } hitcount: 335
+ { pid: 2030, prio: 120, lat: ~ 2^2 } hitcount: 10
+ { pid: 2032, prio: 120, lat: ~ 2^2 } hitcount: 1
+ { pid: 2035, prio: 120, lat: ~ 2^2 } hitcount: 2
+ { pid: 2031, prio: 9, lat: ~ 2^2 } hitcount: 176
+ { pid: 2028, prio: 120, lat: ~ 2^2 } hitcount: 15
+ { pid: 2033, prio: 9, lat: ~ 2^2 } hitcount: 91
+ { pid: 2032, prio: 9, lat: ~ 2^2 } hitcount: 125
+ { pid: 2029, prio: 120, lat: ~ 2^2 } hitcount: 4
+ { pid: 2031, prio: 120, lat: ~ 2^2 } hitcount: 3
+ { pid: 2029, prio: 120, lat: ~ 2^3 } hitcount: 2
+ { pid: 2035, prio: 9, lat: ~ 2^3 } hitcount: 41
+ { pid: 2030, prio: 120, lat: ~ 2^3 } hitcount: 1
+ { pid: 2032, prio: 9, lat: ~ 2^3 } hitcount: 32
+ { pid: 2031, prio: 9, lat: ~ 2^3 } hitcount: 44
+ { pid: 2034, prio: 9, lat: ~ 2^3 } hitcount: 40
+ { pid: 2030, prio: 9, lat: ~ 2^3 } hitcount: 29
+ { pid: 2033, prio: 9, lat: ~ 2^3 } hitcount: 31
+ { pid: 2029, prio: 9, lat: ~ 2^3 } hitcount: 31
+ { pid: 2028, prio: 120, lat: ~ 2^3 } hitcount: 18
+ { pid: 2031, prio: 120, lat: ~ 2^3 } hitcount: 2
+ { pid: 2028, prio: 120, lat: ~ 2^4 } hitcount: 1
+ { pid: 2029, prio: 9, lat: ~ 2^4 } hitcount: 4
+ { pid: 2031, prio: 120, lat: ~ 2^7 } hitcount: 1
+ { pid: 2032, prio: 120, lat: ~ 2^7 } hitcount: 1
+
+ Totals:
+ Hits: 2122
+ Entries: 30
+ Dropped: 0
+
+
+The latency values can also be grouped linearly by a given size with
+the ".buckets" modifier and specify a size (in this case groups of 10).
+
+ # echo 'hist:keys=pid,prio,lat.buckets=10:sort=lat' >> \
+ /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
+
+ # event histogram
+ #
+ # trigger info: hist:keys=pid,prio,lat.buckets=10:vals=hitcount:sort=lat.buckets=10:size=2048 [active]
+ #
+
+ { pid: 2067, prio: 9, lat: ~ 0-9 } hitcount: 220
+ { pid: 2068, prio: 9, lat: ~ 0-9 } hitcount: 157
+ { pid: 2070, prio: 9, lat: ~ 0-9 } hitcount: 100
+ { pid: 2067, prio: 120, lat: ~ 0-9 } hitcount: 6
+ { pid: 2065, prio: 120, lat: ~ 0-9 } hitcount: 2
+ { pid: 2066, prio: 120, lat: ~ 0-9 } hitcount: 2
+ { pid: 2069, prio: 9, lat: ~ 0-9 } hitcount: 122
+ { pid: 2069, prio: 120, lat: ~ 0-9 } hitcount: 8
+ { pid: 2070, prio: 120, lat: ~ 0-9 } hitcount: 1
+ { pid: 2068, prio: 120, lat: ~ 0-9 } hitcount: 7
+ { pid: 2066, prio: 9, lat: ~ 0-9 } hitcount: 365
+ { pid: 2064, prio: 120, lat: ~ 0-9 } hitcount: 35
+ { pid: 2065, prio: 9, lat: ~ 0-9 } hitcount: 998
+ { pid: 2071, prio: 9, lat: ~ 0-9 } hitcount: 85
+ { pid: 2065, prio: 9, lat: ~ 10-19 } hitcount: 2
+ { pid: 2064, prio: 120, lat: ~ 10-19 } hitcount: 2
+
+ Totals:
+ Hits: 2112
+ Entries: 16
+ Dropped: 0
+
2.2.3 Hist trigger 'handlers' and 'actions'
-------------------------------------------
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a1adb29ef5c1..be0169594de5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5654,6 +5654,7 @@ static const char readme_msg[] =
"\t .execname display a common_pid as a program name\n"
"\t .syscall display a syscall id as a syscall name\n"
"\t .log2 display log2 value rather than raw number\n"
+ "\t .buckets=size display values in groups of size rather than raw number\n"
"\t .usecs display a common_timestamp in microseconds\n\n"
"\t The 'pause' parameter can be used to pause an existing hist\n"
"\t trigger or to start a hist trigger but not log any events\n"

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