Add an 'onmax(var).save(field,...)' hist trigger action which is
invoked whenever an event exceeds the current maximum.
The end result is that the trace event fields or variables specified
as the onmax.save() params will be saved if 'var' exceeds the current
maximum for that hist trigger entry. This allows context from the
event that exhibited the new maximum to be saved for later reference.
When the histogram is displayed, additional fields displaying the
saved values will be printed.
As an example the below defines a couple of hist triggers, one for
sched_wakeup and another for sched_switch, keyed on pid. Whenever a
sched_wakeup occurs, the timestamp is saved in the entry corresponding
to the current pid, and when the scheduler switches back to that pid,
the timestamp difference is calculated. If the resulting latency
exceeds the current maximum latency, the specified save() values are
saved:
# echo 'hist:keys=pid:ts0=common_timestamp.usecs \
if comm=="cyclictest"' >> \
/sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
# echo 'hist:keys=next_pid:\
wakeup_lat=common_timestamp.usecs-$ts0:\
onmax($wakeup_lat).save(next_comm,prev_pid,prev_prio,prev_comm) \
if next_comm=="cyclictest"' >> \
/sys/kernel/debug/tracing/events/sched/sched_switch/trigger
When the histogram is displayed, the max value and the saved values
corresponding to the max are displayed following the rest of the
fields:
# cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
{ next_pid: 3728 } hitcount: 199 \
max: 123 next_comm: cyclictest prev_pid: 0 \
prev_prio: 120 prev_comm: swapper/3
{ next_pid: 3730 } hitcount: 1321 \
max: 15 next_comm: cyclictest prev_pid: 0 \
prev_prio: 120 prev_comm: swapper/1
{ next_pid: 3729 } hitcount: 1973\
max: 25 next_comm: cyclictest prev_pid: 0 \
prev_prio: 120 prev_comm: swapper/0
Totals:
Hits: 3493
Entries: 3
Dropped: 0
Link: http://lkml.kernel.org/r/006907f71b1e839bb059337ec3c496f84fcb71de.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add an 'onmatch(matching.event).<synthetic_event_name>(param list)'
hist trigger action which is invoked with the set of variables or
event fields named in the 'param list'. The result is the generation
of a synthetic event that consists of the values contained in those
variables and/or fields at the time the invoking event was hit.
As an example the below defines a simple synthetic event using a
variable defined on the sched_wakeup_new event, and shows the event
definition with unresolved fields, since the sched_wakeup_new event
with the testpid variable hasn't been defined yet:
# echo 'wakeup_new_test pid_t pid; int prio' >> \
/sys/kernel/debug/tracing/synthetic_events
# cat /sys/kernel/debug/tracing/synthetic_events
wakeup_new_test pid_t pid; int prio
The following hist trigger both defines a testpid variable and
specifies an onmatch() trace action that uses that variable along with
a non-variable field to generate a wakeup_new_test synthetic event
whenever a sched_wakeup_new event occurs, which because of the 'if
comm == "cyclictest"' filter only happens when the executable is
cyclictest:
# echo 'hist:testpid=pid:keys=$testpid:\
onmatch(sched.sched_wakeup_new).wakeup_new_test($testpid, prio) \
if comm=="cyclictest"' >> \
/sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
Creating and displaying a histogram based on those events is now just
a matter of using the fields and new synthetic event in the
tracing/events/synthetic directory, as usual:
# echo 'hist:keys=pid,prio:sort=pid,prio' >> \
/sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger
Link: http://lkml.kernel.org/r/8c2a574bcb7530c876629c901ecd23911b14afe8.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Rajvi Jingar <rajvi.jingar@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Users should be able to directly specify event fields in hist trigger
'actions' rather than being forced to explicitly create a variable for
that purpose.
Add support allowing fields to be used directly in actions, which
essentially does just that - creates 'invisible' variables for each
bare field specified in an action. If a bare field refers to a field
on another (matching) event, it even creates a special histogram for
the purpose (since variables can't be defined on an existing histogram
after histogram creation).
Here's a simple example that demonstrates both. Basically the
onmatch() action creates a list of variables corresponding to the
parameters of the synthetic event to be generated, and then uses those
values to generate the event. So for the wakeup_latency synthetic
event 'call' below the first param, $wakeup_lat, is a variable defined
explicitly on sched_switch, where 'next_pid' is just a normal field on
sched_switch, and prio is a normal field on sched_waking.
Since the mechanism works on variables, those two normal fields just
have 'invisible' variables created internally for them. In the case of
'prio', which is on another event, we actually need to create an
additional hist trigger and define the invisible variable on that, since
once a hist trigger is defined, variables can't be added to it later.
echo 'wakeup_latency u64 lat; pid_t pid; int prio' >>
/sys/kernel/debug/tracing/synthetic_events
echo 'hist:keys=pid:ts0=common_timestamp.usecs >>
/sys/kernel/debug/tracing/events/sched/sched_waking/trigger
echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:
onmatch(sched.sched_waking).wakeup_latency($wakeup_lat,next_pid,prio)
>> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
Link: http://lkml.kernel.org/r/8e8dcdac1ea180ed7a3689e1caeeccede9dc42b3.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Synthetic events are user-defined events generated from hist trigger
variables saved from one or more other events.
To define a synthetic event, the user writes a simple specification
consisting of the name of the new event along with one or more
variables and their type(s), to the tracing/synthetic_events file.
For instance, the following creates a new event named 'wakeup_latency'
with 3 fields: lat, pid, and prio:
# echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \
/sys/kernel/debug/tracing/synthetic_events
Reading the tracing/synthetic_events file lists all the
currently-defined synthetic events, in this case the event we defined
above:
# cat /sys/kernel/debug/tracing/synthetic_events
wakeup_latency u64 lat; pid_t pid; int prio
At this point, the synthetic event is ready to use, and a histogram
can be defined using it:
# 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
Although a histogram can be defined for it, nothing will happen until
an action tracing that event via the trace_synth() function occurs.
The trace_synth() function is very similar to all the other trace_*
invocations spread throughout the kernel, except in this case the
trace_ function and its corresponding tracepoint isn't statically
generated but defined by the user at run-time.
How this can be automatically hooked up via a hist trigger 'action' is
discussed in a subsequent patch.
Link: http://lkml.kernel.org/r/c68df2284b7d172669daf9be29db62ad49bbc559.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
[fix noderef.cocci warnings, sizeof pointer for kcalloc of event->fields]
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add a hook for executing extra actions whenever a histogram entry is
added or updated.
The default 'action' when a hist entry is added to a histogram is to
update the set of values associated with it. Some applications may
want to perform additional actions at that point, such as generate
another event, or compare and save a maximum.
Add a simple framework for doing that; specific actions will be
implemented on top of it in later patches.
Link: http://lkml.kernel.org/r/9482ba6a3eaf5ca6e60954314beacd0e25c05b24.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add the necessary infrastructure to allow the variables defined on one
event to be referenced in another. This allows variables set by a
previous event to be referenced and used in expressions combining the
variable values saved by that previous event and the event fields of
the current event. For example, here's how a latency can be
calculated and saved into yet another variable named 'wakeup_lat':
# echo 'hist:keys=pid,prio:ts0=common_timestamp ...
# echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...
In the first event, the event's timetamp is saved into the variable
ts0. In the next line, ts0 is subtracted from the second event's
timestamp to produce the latency.
Further users of variable references will be described in subsequent
patches, such as for instance how the 'wakeup_lat' variable above can
be displayed in a latency histogram.
Link: http://lkml.kernel.org/r/b1d3e6975374e34d501ff417c20189c3f9b2c7b8.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add support for simple addition, subtraction, and unary expressions
(-(expr) and expr, where expr = b-a, a+b, a+b+c) to hist triggers, in
order to support a minimal set of useful inter-event calculations.
These operations are needed for calculating latencies between events
(timestamp1-timestamp0) and for combined latencies (latencies over 3
or more events).
In the process, factor out some common code from key and value
parsing.
Link: http://lkml.kernel.org/r/9a9308ead4fe32a433d9c7e95921fb798394f6b2.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
[kbuild test robot fix, add static to parse_atom()]
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
[ Replaced '//' comments with normal /* */ comments ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add support for saving the value of a current event's event field by
assigning it to a variable that can be read by a subsequent event.
The basic syntax for saving a variable is to simply prefix a unique
variable name not corresponding to any keyword along with an '=' sign
to any event field.
Both keys and values can be saved and retrieved in this way:
# echo 'hist:keys=next_pid:vals=$ts0:ts0=common_timestamp ...
# echo 'hist:timer_pid=common_pid:key=$timer_pid ...'
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:...
Multiple variables can be assigned at the same time:
# echo 'hist:keys=pid:vals=$ts0,$b,field2:ts0=common_timestamp,b=field1 ...
Multiple (or single) variables can also be assigned at the same time
using separate assignments:
# echo 'hist:keys=pid:vals=$ts0:ts0=common_timestamp:b=field1:c=field2 ...
Variables set as above can be used by being referenced from another
event, as described in a subsequent patch.
Link: http://lkml.kernel.org/r/fc93c4944d9719dbcb1d0067be627d44e98e2adc.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Baohong Liu <baohong.liu@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Appending .usecs onto a common_timestamp field will cause the
timestamp value to be in microseconds instead of the default
nanoseconds. A typical latency histogram using usecs would look like
this:
# echo 'hist:keys=pid,prio:ts0=common_timestamp.usecs ...
# echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0 ...
This also adds an external trace_clock_in_ns() to trace.c for the
timestamp conversion.
Link: http://lkml.kernel.org/r/4e813705a170b3e13e97dc3135047362fb1a39f3.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
In order to allow information to be passed between trace events, add
support for per-element variables to tracing_map. This provides a
means for histograms to associate a value or values with an entry when
it's saved or updated, and retrieved by a subsequent event occurrences.
Variables can be set using tracing_map_set_var() and read using
tracing_map_read_var(). tracing_map_var_set() returns true or false
depending on whether or not the variable has been set or not, which is
important for event-matching applications.
tracing_map_read_var_once() reads the variable and resets it to the
'unset' state, implementing read-once variables, which are also
important for event-matching uses.
Link: http://lkml.kernel.org/r/7fa001108252556f0c6dd9d63145eabfe3370d1a.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add support for a timestamp event field. This is actually a 'pseudo-'
event field in that it behaves like it's part of the event record, but
is really part of the corresponding ring buffer event.
To make use of the timestamp field, users can specify
"common_timestamp" as a field name for any histogram. Note that this
doesn't make much sense on its own either as either a key or value,
but needs to be supported even so, since follow-on patches will add
support for making use of this field in time deltas. The
common_timestamp 'field' is not a bona fide event field - so you won't
find it in the event description - but rather it's a synthetic field
that can be used like a real field.
Note that the use of this field requires the ring buffer be put into
'absolute timestamp' mode, which saves the complete timestamp for each
event rather than an offset. This mode will be enabled if and only if
a histogram makes use of the "common_timestamp" field.
Link: http://lkml.kernel.org/r/97afbd646ed146e26271f3458b4b33e16d7817c2.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Baohong Liu <baohong.liu@intel.com>
[kasan use-after-free fix]
Signed-off-by: Vedang Patel <vedang.patel@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add a new option flag indicating whether or not the ring buffer is in
'absolute timestamp' mode.
Currently this is only set/unset by hist triggers that make use of a
common_timestamp. As such, there's no reason to make this writeable
for users - its purpose is only to allow users to determine
unequivocally whether or not the ring buffer is in that mode (although
absolute timestamps can coexist with the normal delta timestamps, when
the ring buffer is in absolute mode, timestamps written while absolute
mode is in effect take up more space in the buffer, and are not as
efficient).
Link: http://lkml.kernel.org/r/e8aa7b1cde1cf15014e66545d06ac6ef2ebba456.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
RINGBUF_TYPE_TIME_STAMP is defined but not used, and from what I can
gather was reserved for something like an absolute timestamp feature
for the ring buffer, if not a complete replacement of the current
time_delta scheme.
This code redefines RINGBUF_TYPE_TIME_STAMP to implement absolute time
stamps. Another way to look at it is that it essentially forces
extended time_deltas for all events.
The motivation for doing this is to enable time_deltas that aren't
dependent on previous events in the ring buffer, making it feasible to
use the ring_buffer_event timetamps in a more random-access way, for
purposes other than serial event printing.
To set/reset this mode, use tracing_set_timestamp_abs() from the
previous interface patch.
Link: http://lkml.kernel.org/r/477b362dba1ce7fab9889a1a8e885a62c472f041.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Tom Zanussi
Vedang Patel