[PATCH v4 3/5] tracing: Add .percent suffix option to histogram values

Masami Hiramatsu (Google)
2022-08-27T04:03:52Z

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Add .percent suffix option to show the histogram values in percentage.
This feature is useful when we need yo undersntand the overall trend
for the histograms of large values.
E.g. this shows the runtime percentage for each tasks.

------
# cd /sys/kernel/debug/tracing/
# echo hist:keys=pid:vals=hitcount,runtime.percent:sort=pid > \
events/sched/sched_stat_runtime/trigger
# sleep 10
# cat events/sched/sched_stat_runtime/hist
# event histogram
#
# trigger info: hist:keys=pid:vals=hitcount,runtime.percent:sort=pid:size=2048 [active]
#

{ pid: 8 } hitcount: 7 runtime (%): 4.14
{ pid: 14 } hitcount: 5 runtime (%): 3.69
{ pid: 16 } hitcount: 11 runtime (%): 3.41
{ pid: 61 } hitcount: 41 runtime (%): 19.75
{ pid: 65 } hitcount: 4 runtime (%): 1.48
{ pid: 70 } hitcount: 6 runtime (%): 3.60
{ pid: 72 } hitcount: 2 runtime (%): 1.10
{ pid: 144 } hitcount: 10 runtime (%): 32.01
{ pid: 151 } hitcount: 8 runtime (%): 22.66
{ pid: 152 } hitcount: 2 runtime (%): 8.10

Totals:
Hits: 96
Entries: 10
Dropped: 0
-----

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v4:
- Port on the Tom's hitcount patch.
Changes in v3:
- Show "(%)" in the field name.
- Return div0 error only if the value is not zero.
- Simplify the print code with hist_trigger_print_val().
- Show hitcount percentage correctly.
Changes in v2:
- Use div64_*().
- Show an error when failing to calculate the percentage.
---
kernel/trace/trace.c | 3 +
kernel/trace/trace_events_hist.c | 105 +++++++++++++++++++++++++++++++-------
2 files changed, 88 insertions(+), 20 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d3005279165d..5e5efc550ac4 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5700,7 +5700,8 @@ static const char readme_msg[] =
"\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 .usecs display a common_timestamp in microseconds\n"
+ "\t .percent display a number of percentage value\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"
"\t until told to do so. 'continue' can be used to start or\n"
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index e80a41e380bb..af6c140f85e6 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -506,6 +506,7 @@ enum hist_field_flags {
HIST_FIELD_FL_ALIAS = 1 << 16,
HIST_FIELD_FL_BUCKET = 1 << 17,
HIST_FIELD_FL_CONST = 1 << 18,
+ HIST_FIELD_FL_PERCENT = 1 << 19,
};

struct var_defs {
@@ -1707,6 +1708,8 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
flags_str = "buckets";
else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP_USECS)
flags_str = "usecs";
+ else if (hist_field->flags & HIST_FIELD_FL_PERCENT)
+ flags_str = "percent";

return flags_str;
}
@@ -2315,6 +2318,10 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
if (ret || !(*buckets))
goto error;
*flags |= HIST_FIELD_FL_BUCKET;
+ } else if (strncmp(modifier, "percent", 7) == 0) {
+ if (*flags & (HIST_FIELD_FL_VAR | HIST_FIELD_FL_KEY))
+ goto error;
+ *flags |= HIST_FIELD_FL_PERCENT;
} else {
error:
hist_err(tr, HIST_ERR_BAD_FIELD_MODIFIER, errpos(modifier));
@@ -4350,9 +4357,12 @@ static int create_val_fields(struct hist_trigger_data *hist_data,
if (!field_str)
break;

- if (strcmp(field_str, "hitcount") == 0) {
- if (!n_hitcount++)
- continue;
+ if (!n_hitcount++ && strncmp(field_str, "hitcount", 8) == 0 &&
+ (field_str[8] == '.' || field_str[8] == '\0')) {
+ if (strncmp(field_str + 8, ".percent", 8) == 0)
+ hist_data->fields[HITCOUNT_IDX]->flags |=
+ HIST_FIELD_FL_PERCENT;
+ continue;
}

ret = create_val_field(hist_data, j++, file, field_str);
@@ -5288,33 +5298,69 @@ static void hist_trigger_print_key(struct seq_file *m,
seq_puts(m, "}");
}

+/* Get the 100 times of the percentage of @val in @total */
+static inline unsigned int __get_percentage(u64 val, u64 total)
+{
+ if (!total)
+ goto div0;
+
+ if (val < (U64_MAX / 10000))
+ return (unsigned int)div64_ul(val * 10000, total);
+
+ total = div64_u64(total, 10000);
+ if (!total)
+ goto div0;
+
+ return (unsigned int)div64_ul(val, total);
+div0:
+ return val ? UINT_MAX : 0;
+}
+
+static void hist_trigger_print_val(struct seq_file *m, unsigned int idx,
+ const char *field_name, unsigned long flags,
+ u64 *totals, struct tracing_map_elt *elt)
+{
+ u64 val = tracing_map_read_sum(elt, idx);
+ unsigned int pc;
+
+ if (flags & HIST_FIELD_FL_PERCENT) {
+ pc = __get_percentage(val, totals[idx]);
+ if (pc == UINT_MAX)
+ seq_printf(m, " %s (%%):[ERROR]", field_name);
+ else
+ seq_printf(m, " %s (%%): %3u.%02u", field_name,
+ pc / 100, pc % 100);
+ } else if (flags & HIST_FIELD_FL_HEX) {
+ seq_printf(m, " %s: %10llx", field_name, val);
+ } else {
+ seq_printf(m, " %s: %10llu", field_name, val);
+ }
+}
+
static void hist_trigger_entry_print(struct seq_file *m,
struct hist_trigger_data *hist_data,
+ u64 *totals,
void *key,
struct tracing_map_elt *elt)
{
const char *field_name;
- unsigned int i;
+ unsigned int i = HITCOUNT_IDX;
+ unsigned long flags;

hist_trigger_print_key(m, hist_data, key, elt);

- seq_printf(m, " hitcount: %10llu",
- tracing_map_read_sum(elt, HITCOUNT_IDX));
+ flags = hist_data->fields[i]->flags;
+ hist_trigger_print_val(m, i, "hitcount", flags, totals, elt);

for (i = 1; i < hist_data->n_vals; i++) {
field_name = hist_field_name(hist_data->fields[i], 0);
+ flags = hist_data->fields[i]->flags;

- if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR ||
- hist_data->fields[i]->flags & HIST_FIELD_FL_EXPR)
+ if (flags & HIST_FIELD_FL_VAR || flags & HIST_FIELD_FL_EXPR)
continue;

- if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
- seq_printf(m, " %s: %10llx", field_name,
- tracing_map_read_sum(elt, i));
- } else {
- seq_printf(m, " %s: %10llu", field_name,
- tracing_map_read_sum(elt, i));
- }
+ seq_puts(m, " ");
+ hist_trigger_print_val(m, i, field_name, flags, totals, elt);
}

print_actions(m, hist_data, elt);
@@ -5327,7 +5373,8 @@ static int print_entries(struct seq_file *m,
{
struct tracing_map_sort_entry **sort_entries = NULL;
struct tracing_map *map = hist_data->map;
- int i, n_entries;
+ int i, j, n_entries;
+ u64 *totals = NULL;

n_entries = tracing_map_sort_entries(map, hist_data->sort_keys,
hist_data->n_sort_keys,
@@ -5335,11 +5382,29 @@ static int print_entries(struct seq_file *m,
if (n_entries < 0)
return n_entries;

+ for (j = 0; j < hist_data->n_vals; j++) {
+ if (!(hist_data->fields[j]->flags & HIST_FIELD_FL_PERCENT))
+ continue;
+ if (!totals) {
+ totals = kcalloc(hist_data->n_vals, sizeof(u64),
+ GFP_KERNEL);
+ if (!totals) {
+ n_entries = -ENOMEM;
+ goto out;
+ }
+ }
+ for (i = 0; i < n_entries; i++)
+ totals[j] += tracing_map_read_sum(
+ sort_entries[i]->elt, j);
+ }
+
for (i = 0; i < n_entries; i++)
- hist_trigger_entry_print(m, hist_data,
+ hist_trigger_entry_print(m, hist_data, totals,
sort_entries[i]->key,
sort_entries[i]->elt);

+ kfree(totals);
+out:
tracing_map_destroy_sort_entries(sort_entries, n_entries);

return n_entries;
@@ -5759,9 +5824,11 @@ static int event_hist_trigger_print(struct seq_file *m,
continue;
}

- if (i == HITCOUNT_IDX)
+ if (i == HITCOUNT_IDX) {
seq_puts(m, "hitcount");
- else {
+ if (field->flags & HIST_FIELD_FL_PERCENT)
+ seq_puts(m, ".percent");
+ } else {
seq_puts(m, ",");
hist_field_print(m, field);
}