On Tue, 5 Sep 2017 16:57:44 -0500
Tom Zanussi <tom.zanu...@linux.intel.com> wrote:
> A common key to use in a histogram is the cpuid - add a new cpu
> 'synthetic' field for that purpose. This field is named cpu rather
> than $cpu or $common_cpu because 'cpu' already exists as a special
> filter field and it makes more sense to match that rather than add
> another name for the same thing.
>
> Signed-off-by: Tom Zanussi <tom.zanu...@linux.intel.com>
> ---
> Documentation/trace/events.txt | 18 ++++++++++++++++++
> kernel/trace/trace_events_hist.c | 30 +++++++++++++++++++++++++++---
> 2 files changed, 45 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
> index 2cc08d4..9717688 100644
> --- a/Documentation/trace/events.txt
> +++ b/Documentation/trace/events.txt
> @@ -668,6 +668,24 @@ The following commands are supported:
> The examples below provide a more concrete illustration of the
> concepts and typical usage patterns discussed above.
>
> + 'synthetic' event fields
> + ------------------------
> +
> + There are a number of 'synthetic fields' available for use as keys
> + or values in a hist trigger. These look like and behave as if they
> + were event fields, but aren't actually part of the event's field
> + definition or format file. They are however available for any
> + event, and can be used anywhere an actual event field could be.
> + 'Synthetic' field names are always prefixed with a '$' character to
> + indicate that they're not normal fields (with the exception of
> + 'cpu', for compatibility with existing filter usage):
> +
> + $common_timestamp u64 - timestamp (from ring buffer) associated
> + with the event, in nanoseconds. May be
> + modified by .usecs to have timestamps
> + interpreted as microseconds.
I guess the above should have been added with the synthetic field
addition.
> + cpu int - the cpu on which the event occurred.
Then this (and the explanation of '$' for cpu above) should be added
with this patch.
> +
>
> 6.2 'hist' trigger examples
> ---------------------------
> diff --git a/kernel/trace/trace_events_hist.c
> b/kernel/trace/trace_events_hist.c
> index 4f66f2e..0782766 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -226,6 +226,7 @@ enum hist_field_flags {
> HIST_FIELD_FL_VAR_ONLY = 8192,
> HIST_FIELD_FL_EXPR = 16384,
> HIST_FIELD_FL_VAR_REF = 32768,
> + HIST_FIELD_FL_CPU = 65536,
> };
>
> struct var_defs {
> @@ -1170,6 +1171,16 @@ 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 = raw_smp_processor_id();
Hmm, I wonder if this should be just smp_processor_id(). Why have the
raw_?
> +
> + return cpu;
> +}
> +
> static struct hist_field *check_var_ref(struct hist_field *hist_field,
> struct hist_trigger_data *var_data,
> unsigned int var_idx)
> @@ -1518,6 +1529,8 @@ 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 = "$common_timestamp";
> + else if (field->flags & HIST_FIELD_FL_CPU)
> + field_name = "cpu";
> else if (field->flags & HIST_FIELD_FL_EXPR ||
> field->flags & HIST_FIELD_FL_VAR_REF)
> field_name = field->name;
> @@ -1990,6 +2003,15 @@ static struct hist_field *create_hist_field(struct
> hist_trigger_data *hist_data,
> goto out;
> }
>
> + if (flags & HIST_FIELD_FL_CPU) {
> + hist_field->fn = hist_field_cpu;
> + hist_field->size = sizeof(int);
> + hist_field->type = kstrdup("int", GFP_KERNEL);
> + if (!hist_field->type)
> + goto free;
> + goto out;
> + }
> +
> if (WARN_ON_ONCE(!field))
> goto out;
>
> @@ -2182,7 +2204,9 @@ static struct hist_field *parse_var_ref(struct
> trace_array *tr,
> hist_data->enable_timestamps = true;
> if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
> hist_data->attrs->ts_in_usecs = true;
> - } else {
> + } else if (strcmp(field_name, "cpu") == 0)
> + *flags |= HIST_FIELD_FL_CPU;
> + else {
> field = trace_find_event_field(file->event_call, field_name);
> if (!field || !field->size) {
> field = ERR_PTR(-EINVAL);
> @@ -3185,7 +3209,6 @@ static int onmatch_create(struct hist_trigger_data
> *hist_data,
> goto out;
> }
> }
> -
> if (param[0] == '$')
> hist_field = onmatch_find_var(hist_data, data, system,
> event_name, param);
> @@ -3200,7 +3223,6 @@ static int onmatch_create(struct hist_trigger_data
> *hist_data,
> ret = -EINVAL;
> goto out;
> }
> -
Why the modification of whitespace here?
-- Steve
> if (check_synth_field(event, hist_field, field_pos) == 0) {
> var_ref = create_var_ref(hist_field);
> if (!var_ref) {
> @@ -4315,6 +4337,8 @@ 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)
> seq_printf(m, "%s", field_name);
>
