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tracing: Add cpu field for hist triggers

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A common key to use in a histogram is the cpuid - add a new cpu
'synthetic' field named 'cpu' for that purpose.

Link: http://lkml.kernel.org/r/89537645bfc957e0d76e2cacf5f0ada88691a6cc.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>
This commit is contained in:
Tom Zanussi 2018-01-15 20:52:03 -06:00 committed by Steven Rostedt (VMware)
parent ec5ce09875
commit 8b7622bf94
2 changed files with 42 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

15
Documentation/trace/histogram.txt
View file

@ -172,6 +172,21 @@
The examples below provide a more concrete illustration of the
concepts and typical usage patterns discussed above.
'special' event fields
------------------------
There are a number of 'special event fields' available for use as
keys or values in a hist trigger. These look like and behave as if
they were actual event fields, but aren't really part of the event's
field definition or format file. They are however available for any
event, and can be used anywhere an actual event field could be.
They are:
common_timestamp u64 - timestamp (from ring buffer) associated
with the event, in nanoseconds. May be
modified by .usecs to have timestamps
interpreted as microseconds.
cpu int - the cpu on which the event occurred.
6.2 'hist' trigger examples
---------------------------

28
kernel/trace/trace_events_hist.c
View file

@ -227,6 +227,7 @@ enum hist_field_flags {
HIST_FIELD_FL_VAR = 1 << 12,
HIST_FIELD_FL_EXPR = 1 << 13,
HIST_FIELD_FL_VAR_REF = 1 << 14,
HIST_FIELD_FL_CPU = 1 << 15,
};
struct var_defs {
@ -1164,6 +1165,16 @@ static u64 hist_field_timestamp(struct hist_field *hist_field,
return ts;
}
static u64 hist_field_cpu(struct hist_field *hist_field,
struct tracing_map_elt *elt,
struct ring_buffer_event *rbe,
void *event)
{
int cpu = smp_processor_id();
return cpu;
}
static struct hist_field *
check_field_for_var_ref(struct hist_field *hist_field,
struct hist_trigger_data *var_data,
@ -1602,6 +1613,8 @@ static const char *hist_field_name(struct hist_field *field,
field_name = hist_field_name(field->operands[0], ++level);
else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
field_name = "common_timestamp";
else if (field->flags & HIST_FIELD_FL_CPU)
field_name = "cpu";
else if (field->flags & HIST_FIELD_FL_EXPR ||
field->flags & HIST_FIELD_FL_VAR_REF) {
if (field->system) {
@ -2109,6 +2122,15 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
goto out;
}
if (flags & HIST_FIELD_FL_CPU) {
hist_field->fn = hist_field_cpu;
hist_field->size = sizeof(int);
hist_field->type = kstrdup("unsigned int", GFP_KERNEL);
if (!hist_field->type)
goto free;
goto out;
}
if (WARN_ON_ONCE(!field))
goto out;
@ -2345,7 +2367,9 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
hist_data->enable_timestamps = true;
if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
hist_data->attrs->ts_in_usecs = true;
} else {
} else if (strcmp(field_name, "cpu") == 0)
*flags |= HIST_FIELD_FL_CPU;
else {
field = trace_find_event_field(file->event_call, field_name);
if (!field || !field->size) {
field = ERR_PTR(-EINVAL);
@ -4619,6 +4643,8 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP)
seq_puts(m, "common_timestamp");
else if (hist_field->flags & HIST_FIELD_FL_CPU)
seq_puts(m, "cpu");
else if (field_name) {
if (hist_field->flags & HIST_FIELD_FL_VAR_REF)
seq_putc(m, '$');