[PATCH] tracing: Add "grouping" to histogram logic
From: Steven Rostedt
Date: Fri Jul 02 2021 - 17:56:54 EST
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
There's been several times I wished the histogram logic had a "grouping"
feature for the buckets. Currently, each bucket has a size of one. That
is, if you trace the amount of requested allocations, each allocation is
its own bucket, even if you are interested in what allocates 100 bytes or
less, 100 to 200, 200 to 300, etc.
Also, without grouping, it fills up the allocated histogram buckets
quickly. If you are tracking latency, and don't care if something is 200
microseconds off, or 201 microseconds off, but want to track them by say
10 microseconds each. This can not currently be done.
Introduce a "grouping" command to each field where it will record in a
rounded number. For example:
># echo 'hist:keys=bytes_req-100:sort=bytes_req' > events/kmem/kmalloc/trigger
># cat events/kmem/kmalloc/hist
# event histogram
#
# trigger info:
hist:keys=bytes_req-100:vals=hitcount:sort=bytes_req-100:size=2048
[active]
#
{ bytes_req: 0-99 } hitcount: 7207
{ bytes_req: 100-199 } hitcount: 1030
{ bytes_req: 200-299 } hitcount: 602
{ bytes_req: 300-399 } hitcount: 414
{ bytes_req: 400-499 } hitcount: 584
{ bytes_req: 500-599 } hitcount: 35
{ bytes_req: 600-699 } hitcount: 361
{ bytes_req: 700-799 } hitcount: 37
{ bytes_req: 800-899 } hitcount: 26
{ bytes_req: 900-999 } hitcount: 15
{ bytes_req: 1100-1199 } hitcount: 4
{ bytes_req: 1200-1299 } hitcount: 102
{ bytes_req: 1300-1399 } hitcount: 2
{ bytes_req: 1400-1499 } hitcount: 15
{ bytes_req: 1500-1599 } hitcount: 100
{ bytes_req: 1600-1699 } hitcount: 1
{ bytes_req: 1700-1799 } hitcount: 3
{ bytes_req: 1800-1899 } hitcount: 10
{ bytes_req: 2000-2099 } hitcount: 19
{ bytes_req: 2100-2199 } hitcount: 3
{ bytes_req: 2500-2599 } hitcount: 72
{ bytes_req: 2900-2999 } hitcount: 1
{ bytes_req: 3300-3399 } hitcount: 4
{ bytes_req: 3900-3999 } hitcount: 2
{ bytes_req: 4000-4099 } hitcount: 1761
{ bytes_req: 4600-4699 } hitcount: 65
{ bytes_req: 5000-5099 } hitcount: 3
{ bytes_req: 6500-6599 } hitcount: 1
{ bytes_req: 8100-8199 } hitcount: 1
{ bytes_req: 9800-9899 } hitcount: 1
Totals:
Hits: 12481
Entries: 30
Dropped: 0
This finally makes the histograms actual histograms!
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
kernel/trace/trace_events_hist.c | 34 ++++++++++++++++++++++++++++----
1 file changed, 30 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index ba03b7d84fc2..d6e644df9506 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -120,6 +120,7 @@ struct hist_field {
unsigned int size;
unsigned int offset;
unsigned int is_signed;
+ unsigned long grouping;
const char *type;
struct hist_field *operands[HIST_FIELD_OPERANDS_MAX];
struct hist_trigger_data *hist_data;
@@ -3761,6 +3762,7 @@ static int create_key_field(struct hist_trigger_data *hist_data,
{
struct trace_array *tr = hist_data->event_file->tr;
struct hist_field *hist_field = NULL;
+ char *field;
unsigned long flags = 0;
unsigned int key_size;
int ret = 0;
@@ -3768,14 +3770,16 @@ static int create_key_field(struct hist_trigger_data *hist_data,
if (WARN_ON(key_idx >= HIST_FIELDS_MAX))
return -EINVAL;
+ field = strsep(&field_str, "-");
+
flags |= HIST_FIELD_FL_KEY;
- if (strcmp(field_str, "stacktrace") == 0) {
+ if (strcmp(field, "stacktrace") == 0) {
flags |= HIST_FIELD_FL_STACKTRACE;
key_size = sizeof(unsigned long) * HIST_STACKTRACE_DEPTH;
hist_field = create_hist_field(hist_data, NULL, flags, NULL);
} else {
- hist_field = parse_expr(hist_data, file, field_str, flags,
+ hist_field = parse_expr(hist_data, file, field, flags,
NULL, 0);
if (IS_ERR(hist_field)) {
ret = PTR_ERR(hist_field);
@@ -3783,7 +3787,7 @@ static int create_key_field(struct hist_trigger_data *hist_data,
}
if (field_has_hist_vars(hist_field, 0)) {
- hist_err(tr, HIST_ERR_INVALID_REF_KEY, errpos(field_str));
+ hist_err(tr, HIST_ERR_INVALID_REF_KEY, errpos(field));
destroy_hist_field(hist_field, 0);
ret = -EINVAL;
goto out;
@@ -3792,6 +3796,14 @@ static int create_key_field(struct hist_trigger_data *hist_data,
key_size = hist_field->size;
}
+ if (field_str) {
+ unsigned long grouping;
+
+ ret = kstrtoul(field_str, 0, &grouping);
+ if (!ret)
+ hist_field->grouping = grouping;
+ }
+
hist_data->fields[key_idx] = hist_field;
key_size = ALIGN(key_size, sizeof(u64));
@@ -4548,8 +4560,18 @@ static void event_hist_trigger(struct event_trigger_data *data,
if (key_field->flags & HIST_FIELD_FL_STRING) {
key = (void *)(unsigned long)field_contents;
use_compound_key = true;
- } else
+ } else {
+ if (key_field->grouping) {
+ unsigned long grouping = key_field->grouping;
+
+ if (field_contents >= LONG_MAX)
+ field_contents = div64_ul(field_contents, grouping);
+ else
+ field_contents = (u64)((unsigned long)field_contents / grouping);
+ field_contents *= grouping;
+ }
key = (void *)&field_contents;
+ }
}
if (use_compound_key)
@@ -4663,6 +4685,8 @@ static void hist_trigger_print_key(struct seq_file *m,
} else {
uval = *(u64 *)(key + key_field->offset);
seq_printf(m, "%s: %10llu", field_name, uval);
+ if (key_field->grouping)
+ seq_printf(m, "-%llu", uval + key_field->grouping - 1);
}
}
@@ -5096,6 +5120,8 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
seq_printf(m, ".%s", flags);
}
}
+ if (hist_field->grouping)
+ seq_printf(m, "-%ld", hist_field->grouping);
}
static int event_hist_trigger_print(struct seq_file *m,
--
2.31.1