Kernel/linux-next
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git synced 2025-01-01 10:42:11 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

perf ftrace latency: Add --max-latency option

Browse Source 
This patch adds a max-latency option as discussed, in case the number of
buckets is more than 22, we don't observe the setting (for now, let's
say).

By default or if 0 is passed, the value is automatically determined
based on the number of buckets, range and minimum, so that we fill all
available buffers (equivalent to the behaviour before this patch).

We now get something like this:

  # perf ftrace latency --bucket-range=20 \
			--min-latency 10 \
			--max-latency=100 \
			-T switch_mm_irqs_off -a sleep 2
  #   DURATION     |      COUNT | GRAPH             |
       0 -   10 us |       1731 | ################  |
      10 -   30 us |          1 |                   |
      30 -   50 us |          0 |                   |
      50 -   70 us |          0 |                   |
      70 -   90 us |          0 |                   |
      90 -  100 us |          0 |                   |
     100 -  ... us |          0 |                   |

Note the maximum is observed also if it doesn't cover completely a full
range (the second to last range is 10us long to let the last start at
100 sharp), this looks to me more sensible and eases the computations,
since we don't need to account for the range while filling the buckets.

Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20241112181214.1171244-5-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Gabriele Monaco 2024-11-12 15:12:14 -03:00 committed by Arnaldo Carvalho de Melo
parent 08b875b6bf
commit 690a052a6d
4 changed files with 33 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
tools/perf/Documentation/perf-ftrace.txt
View File

@ -155,6 +155,10 @@ OPTIONS for 'perf ftrace latency'
Minimum latency for the start of the first bucket, in ms or ns (according to
-n/--use-nsec).
--max-latency=::
Maximum latency for the start of the last bucket, in ms or ns (according to
-n/--use-nsec). The setting is ignored if the value results in more than
22 buckets.
OPTIONS for 'perf ftrace profile'
---------------------------------

28
tools/perf/builtin-ftrace.c
View File

@ -730,6 +730,7 @@ static void make_histogram(struct perf_ftrace *ftrace, int buckets[],
char *buf, size_t len, char *linebuf)
{
int min_latency = ftrace->min_latency;
int max_latency = ftrace->max_latency;
char *p, *q;
char *unit;
double num;
@ -794,7 +795,7 @@ static void make_histogram(struct perf_ftrace *ftrace, int buckets[],
if (num > 0) // 1st entry: [ 1 unit .. bucket_range units ]
i = num / ftrace->bucket_range + 1;
}
if (i >= NUM_BUCKET)
if (i >= NUM_BUCKET || num >= max_latency - min_latency)
i = NUM_BUCKET - 1;
do_inc:
@ -837,7 +838,7 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
buckets[0], bar_len, bar, bar_total - bar_len, "");
for (i = 1; i < NUM_BUCKET - 1; i++) {
int start, stop;
unsigned int start, stop;
const char *unit = use_nsec ? "ns" : "us";
if (!ftrace->bucket_range) {
@ -853,6 +854,11 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
start = (i - 1) * ftrace->bucket_range + min_latency;
stop = i * ftrace->bucket_range + min_latency;
if (start >= ftrace->max_latency)
break;
if (stop > ftrace->max_latency)
stop = ftrace->max_latency;
if (start >= 1000) {
double dstart = start / 1000.0,
dstop = stop / 1000.0;
@ -873,7 +879,9 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
if (!ftrace->bucket_range) {
printf(" %4d - %-4s %s", 1, "...", use_nsec ? "ms" : "s ");
} else {
int upper_outlier = (NUM_BUCKET - 2) * ftrace->bucket_range + min_latency;
unsigned int upper_outlier = (NUM_BUCKET - 2) * ftrace->bucket_range + min_latency;
if (upper_outlier > ftrace->max_latency)
upper_outlier = ftrace->max_latency;
if (upper_outlier >= 1000) {
double dstart = upper_outlier / 1000.0;
@ -1609,6 +1617,8 @@ int cmd_ftrace(int argc, const char **argv)
"Bucket range in ms or ns (-n/--use-nsec), default is log2() mode"),
OPT_UINTEGER(0, "min-latency", &ftrace.min_latency,
"Minimum latency (1st bucket). Works only with --bucket-range."),
OPT_UINTEGER(0, "max-latency", &ftrace.max_latency,
"Maximum latency (last bucket). Works only with --bucket-range and total buckets less than 22."),
OPT_PARENT(common_options),
};
const struct option profile_options[] = {
@ -1715,6 +1725,18 @@ int cmd_ftrace(int argc, const char **argv)
/* default min latency should be the bucket range */
ftrace.min_latency = ftrace.bucket_range;
}
if (!ftrace.bucket_range && ftrace.max_latency) {
pr_err("--max-latency works only with --bucket-range\n");
parse_options_usage(ftrace_usage, options,
"max-latency", /*short_opt=*/false);
ret = -EINVAL;
goto out_delete_filters;
}
if (!ftrace.max_latency) {
/* default max latency should depend on bucket range and num_buckets */
ftrace.max_latency = (NUM_BUCKET - 2) * ftrace.bucket_range +
ftrace.min_latency;
}
cmd_func = __cmd_latency;
break;
case PERF_FTRACE_PROFILE:

4
tools/perf/util/bpf_skel/func_latency.bpf.c
View File

@ -43,6 +43,7 @@ const volatile int has_task = 0;
const volatile int use_nsec = 0;
const volatile unsigned int bucket_range;
const volatile unsigned int min_latency;
const volatile unsigned int max_latency;
SEC("kprobe/func")
int BPF_PROG(func_begin)
@ -116,7 +117,8 @@ int BPF_PROG(func_end)
// than the min latency desired.
if (delta > 0) { // 1st entry: [ 1 unit .. bucket_range units )
key = delta / bucket_range + 1;
if (key >= NUM_BUCKET)
if (key >= NUM_BUCKET ||
delta >= max_latency - min_latency)
key = NUM_BUCKET - 1;
}
goto do_lookup;

1
tools/perf/util/ftrace.h
View File

@ -22,6 +22,7 @@ struct perf_ftrace {
bool use_nsec;
unsigned int bucket_range;
unsigned int min_latency;
unsigned int max_latency;
int graph_depth;
int func_stack_trace;
int func_irq_info;