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Message-ID: <20241112181214.1171244-4-acme@kernel.org>
Date: Tue, 12 Nov 2024 15:12:13 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Jiri Olsa <jolsa@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Kan Liang <kan.liang@...ux.intel.com>,
Clark Williams <williams@...hat.com>,
linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Gabriele Monaco <gmonaco@...hat.com>
Subject: [PATCH 3/4] perf ftrace latency: Introduce --min-latency to narrow down into a latency range
From: Arnaldo Carvalho de Melo <acme@...hat.com>
Things below and over will be in the first and last, outlier, buckets.
Without it:
# perf ftrace latency --use-nsec --use-bpf \
--bucket-range=200 \
-T switch_mm_irqs_off -a sleep 2
# DURATION | COUNT | GRAPH |
0 - 200 ns | 0 | |
200 - 400 ns | 44 | |
400 - 600 ns | 291 | # |
600 - 800 ns | 506 | ## |
800 - 1000 ns | 148 | |
1.00 - 1.20 us | 581 | ## |
1.20 - 1.40 us | 2199 | ########## |
1.40 - 1.60 us | 1048 | #### |
1.60 - 1.80 us | 1448 | ###### |
1.80 - 2.00 us | 1091 | ##### |
2.00 - 2.20 us | 517 | ## |
2.20 - 2.40 us | 318 | # |
2.40 - 2.60 us | 370 | # |
2.60 - 2.80 us | 271 | # |
2.80 - 3.00 us | 150 | |
3.00 - 3.20 us | 85 | |
3.20 - 3.40 us | 48 | |
3.40 - 3.60 us | 40 | |
3.60 - 3.80 us | 22 | |
3.80 - 4.00 us | 13 | |
4.00 - 4.20 us | 14 | |
4.20 - ... us | 626 | ## |
#
# perf ftrace latency --use-nsec --use-bpf \
--bucket-range=20 --min-latency=1200 \
-T switch_mm_irqs_off -a sleep 2
# DURATION | COUNT | GRAPH |
0 - 1200 ns | 1243 | ##### |
1.20 - 1.22 us | 141 | |
1.22 - 1.24 us | 202 | |
1.24 - 1.26 us | 209 | |
1.26 - 1.28 us | 219 | |
1.28 - 1.30 us | 208 | |
1.30 - 1.32 us | 245 | # |
1.32 - 1.34 us | 246 | # |
1.34 - 1.36 us | 224 | # |
1.36 - 1.38 us | 219 | |
1.38 - 1.40 us | 206 | |
1.40 - 1.42 us | 190 | |
1.42 - 1.44 us | 190 | |
1.44 - 1.46 us | 146 | |
1.46 - 1.48 us | 140 | |
1.48 - 1.50 us | 125 | |
1.50 - 1.52 us | 115 | |
1.52 - 1.54 us | 102 | |
1.54 - 1.56 us | 87 | |
1.56 - 1.58 us | 90 | |
1.58 - 1.60 us | 85 | |
1.60 - ... us | 5487 | ######################## |
#
Now we want focus on the latencies starting at 1.2us, with a finer
grained range of 20ns:
This is all on a live system, so statistically interesting, but not
narrowing down on the same numbers, so a 'perf ftrace latency record'
seems interesting to then use all on the same snapshot of latencies.
A --max-latency counterpart should come next, at first limiting the
max-latency to 20 * bucket-size, as we have a fixed buckets array with
20 + 2 entries (+ for the outliers) and thus would need to make it
larger for higher latencies.
We also may need a way to ask for not considering the out of range
values (first and last buckets) when drawing the buckets bars.
Co-developed-by: Gabriele Monaco <gmonaco@...hat.com>
Signed-off-by: Gabriele Monaco <gmonaco@...hat.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Ian Rogers <irogers@...gle.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Kan Liang <kan.liang@...ux.intel.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
tools/perf/Documentation/perf-ftrace.txt | 4 +++
tools/perf/builtin-ftrace.c | 32 +++++++++++++++++----
tools/perf/util/bpf_ftrace.c | 1 +
tools/perf/util/bpf_skel/func_latency.bpf.c | 12 ++++++--
tools/perf/util/ftrace.h | 1 +
5 files changed, 43 insertions(+), 7 deletions(-)
diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
index e8cc8208e29fca7e..82219e4262c73bc2 100644
--- a/tools/perf/Documentation/perf-ftrace.txt
+++ b/tools/perf/Documentation/perf-ftrace.txt
@@ -151,6 +151,10 @@ OPTIONS for 'perf ftrace latency'
--bucket-range=::
Bucket range in ms or ns (according to -n/--use-nsec), default is log2() mode.
+--min-latency=::
+ Minimum latency for the start of the first bucket, in ms or ns (according to
+ -n/--use-nsec).
+
OPTIONS for 'perf ftrace profile'
---------------------------------
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index e047e5dcda2656df..d9fbe7a329268572 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -729,6 +729,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace)
static void make_histogram(struct perf_ftrace *ftrace, int buckets[],
char *buf, size_t len, char *linebuf)
{
+ int min_latency = ftrace->min_latency;
char *p, *q;
char *unit;
double num;
@@ -777,6 +778,12 @@ static void make_histogram(struct perf_ftrace *ftrace, int buckets[],
if (ftrace->use_nsec)
num *= 1000;
+ i = 0;
+ if (num < min_latency)
+ goto do_inc;
+
+ num -= min_latency;
+
if (!ftrace->bucket_range) {
i = log2(num);
if (i < 0)
@@ -784,13 +791,13 @@ static void make_histogram(struct perf_ftrace *ftrace, int buckets[],
} else {
// Less than 1 unit (ms or ns), or, in the future,
// than the min latency desired.
- i = 0;
if (num > 0) // 1st entry: [ 1 unit .. bucket_range units ]
i = num / ftrace->bucket_range + 1;
}
if (i >= NUM_BUCKET)
i = NUM_BUCKET - 1;
+do_inc:
buckets[i]++;
next:
@@ -804,6 +811,7 @@ static void make_histogram(struct perf_ftrace *ftrace, int buckets[],
static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
{
+ int min_latency = ftrace->min_latency;
bool use_nsec = ftrace->use_nsec;
int i;
int total = 0;
@@ -825,7 +833,8 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
bar_len = buckets[0] * bar_total / total;
printf(" %4d - %4d %s | %10d | %.*s%*s |\n",
- 0, 1, use_nsec ? "ns" : "us", buckets[0], bar_len, bar, bar_total - bar_len, "");
+ 0, min_latency, use_nsec ? "ns" : "us",
+ buckets[0], bar_len, bar, bar_total - bar_len, "");
for (i = 1; i < NUM_BUCKET - 1; i++) {
int start, stop;
@@ -841,8 +850,8 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
unit = use_nsec ? "us" : "ms";
}
} else {
- start = (i - 1) * ftrace->bucket_range + 1;
- stop = i * ftrace->bucket_range + 1;
+ start = (i - 1) * ftrace->bucket_range + min_latency;
+ stop = i * ftrace->bucket_range + min_latency;
if (start >= 1000) {
double dstart = start / 1000.0,
@@ -864,7 +873,7 @@ 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;
+ int upper_outlier = (NUM_BUCKET - 2) * ftrace->bucket_range + min_latency;
if (upper_outlier >= 1000) {
double dstart = upper_outlier / 1000.0;
@@ -1598,6 +1607,8 @@ int cmd_ftrace(int argc, const char **argv)
"Use nano-second histogram"),
OPT_UINTEGER(0, "bucket-range", &ftrace.bucket_range,
"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_PARENT(common_options),
};
const struct option profile_options[] = {
@@ -1693,6 +1704,17 @@ int cmd_ftrace(int argc, const char **argv)
ret = -EINVAL;
goto out_delete_filters;
}
+ if (!ftrace.bucket_range && ftrace.min_latency) {
+ pr_err("--min-latency works only with --bucket-range\n");
+ parse_options_usage(ftrace_usage, options,
+ "min-latency", /*short_opt=*/false);
+ ret = -EINVAL;
+ goto out_delete_filters;
+ }
+ if (!ftrace.min_latency) {
+ /* default min latency should be the bucket range */
+ ftrace.min_latency = ftrace.bucket_range;
+ }
cmd_func = __cmd_latency;
break;
case PERF_FTRACE_PROFILE:
diff --git a/tools/perf/util/bpf_ftrace.c b/tools/perf/util/bpf_ftrace.c
index b3cb68295e56631c..bc484e65fb8f69ca 100644
--- a/tools/perf/util/bpf_ftrace.c
+++ b/tools/perf/util/bpf_ftrace.c
@@ -37,6 +37,7 @@ int perf_ftrace__latency_prepare_bpf(struct perf_ftrace *ftrace)
}
skel->rodata->bucket_range = ftrace->bucket_range;
+ skel->rodata->min_latency = ftrace->min_latency;
/* don't need to set cpu filter for system-wide mode */
if (ftrace->target.cpu_list) {
diff --git a/tools/perf/util/bpf_skel/func_latency.bpf.c b/tools/perf/util/bpf_skel/func_latency.bpf.c
index 00a340ca1543dff0..a89d2b4c38174c03 100644
--- a/tools/perf/util/bpf_skel/func_latency.bpf.c
+++ b/tools/perf/util/bpf_skel/func_latency.bpf.c
@@ -42,6 +42,7 @@ const volatile int has_cpu = 0;
const volatile int has_task = 0;
const volatile int use_nsec = 0;
const volatile unsigned int bucket_range;
+const volatile unsigned int min_latency;
SEC("kprobe/func")
int BPF_PROG(func_begin)
@@ -93,7 +94,7 @@ int BPF_PROG(func_end)
start = bpf_map_lookup_elem(&functime, &tid);
if (start) {
__s64 delta = bpf_ktime_get_ns() - *start;
- __u32 key;
+ __u32 key = 0;
__u64 *hist;
bpf_map_delete_elem(&functime, &tid);
@@ -103,9 +104,16 @@ int BPF_PROG(func_end)
if (bucket_range != 0) {
delta /= cmp_base;
+
+ if (min_latency > 0) {
+ if (delta > min_latency)
+ delta -= min_latency;
+ else
+ goto do_lookup;
+ }
+
// Less than 1 unit (ms or ns), or, in the future,
// than the min latency desired.
- key = 0;
if (delta > 0) { // 1st entry: [ 1 unit .. bucket_range units )
key = delta / bucket_range + 1;
if (key >= NUM_BUCKET)
diff --git a/tools/perf/util/ftrace.h b/tools/perf/util/ftrace.h
index 6ac136484349a9a5..78d7745d497a8988 100644
--- a/tools/perf/util/ftrace.h
+++ b/tools/perf/util/ftrace.h
@@ -21,6 +21,7 @@ struct perf_ftrace {
bool inherit;
bool use_nsec;
unsigned int bucket_range;
+ unsigned int min_latency;
int graph_depth;
int func_stack_trace;
int func_irq_info;
--
2.47.0
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