lkml.org 
[lkml]   [2021]   [Nov]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC 1/3] perf tools: Fix weight sort key behavior
Date
Currently, the weight field in the perf sample has latency information
for some instructions like in memory access. And perf tool has weight
and local_weight sort keys to display the info.

But it's somewhat confusing what it shows exactly. In my understanding,
the local_weight shows a weight in a single sample, and (global) weight
shows a sum of the weights in the hist_entry.

For example,

$ perf mem record -t load dd if=/dev/zero of=/dev/null bs=4k count=1M

$ perf report --stdio -n -s +local_weight
...
#
# Overhead Samples Command Shared Object Symbol Local Weight
# ........ ............ ....... ................ ................................... ............
#
21.23% 313 dd [kernel.vmlinux] [k] lockref_get_not_zero 32
12.43% 183 dd [kernel.vmlinux] [k] lockref_get_not_zero 35
11.97% 159 dd [kernel.vmlinux] [k] lockref_get_not_zero 36
10.40% 141 dd [kernel.vmlinux] [k] lockref_put_return 32
7.63% 113 dd [kernel.vmlinux] [k] lockref_get_not_zero 33
6.37% 92 dd [kernel.vmlinux] [k] lockref_get_not_zero 34
6.15% 90 dd [kernel.vmlinux] [k] lockref_put_return 33
...

So let's look at the lockref_get_not_zero symbols. The top entry shows
that 313 samples were captured with local_weight 32, so the total weight
should be 313 x 32 = 10016. But it's not the case like below:

$ perf report --stdio -n -s +local_weight,weight -S lockref_get_not_zero
...
#
# Overhead Samples Command Shared Object Local Weight Weight
# ........ ............ ....... ................ ............ ............
#
1.36% 4 dd [kernel.vmlinux] 36 144
0.47% 4 dd [kernel.vmlinux] 37 148
0.42% 4 dd [kernel.vmlinux] 32 128
0.40% 4 dd [kernel.vmlinux] 34 136
0.35% 4 dd [kernel.vmlinux] 36 144
0.34% 4 dd [kernel.vmlinux] 35 140
0.30% 4 dd [kernel.vmlinux] 36 144
0.30% 4 dd [kernel.vmlinux] 34 136
0.30% 4 dd [kernel.vmlinux] 32 128
0.30% 4 dd [kernel.vmlinux] 32 128
...

With 'weight' sort key, it's divided to 4 samples even with same info
(comm,dso,sym and local_weight). I don't think this is what we want.

I found this is because of the way it aggregate the weight value.
Since it's not a period, we should not add them in the he->stat.
Otherwise, two 32 weight entries will create a 64 weight entry.

After that, new 32 weight samples don't have a matching entry so it'd
create a new entry and make it a 64 weight entry again and again.
Later, they will be merged into 128 weight entries during the
hists__collapse_resort() with 4 samples, multiple times like above.

Let's keep the weight and display differently. For local_weight, it
can show the weight as is, and for (global) weight it can display the
number multiplied by the number of samples.

With this change, I can see the expected numbers.

$ perf report --stdio -n -s +local_weight,weight -S lockref_get_not_zero
...
#
# Overhead Samples Command Shared Object Local Weight Weight
# ........ ............ ....... ................ ............ ............
#
21.23% 313 dd [kernel.vmlinux] 32 10016
12.43% 183 dd [kernel.vmlinux] 35 6405
11.97% 159 dd [kernel.vmlinux] 36 5724
7.63% 113 dd [kernel.vmlinux] 33 3729
6.37% 92 dd [kernel.vmlinux] 34 3128
4.17% 59 dd [kernel.vmlinux] 37 2183
0.08% 1 dd [kernel.vmlinux] 269 269
0.08% 1 dd [kernel.vmlinux] 38 38

Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/util/hist.c | 14 +++++---------
tools/perf/util/sort.c | 24 +++++++-----------------
tools/perf/util/sort.h | 2 +-
3 files changed, 13 insertions(+), 27 deletions(-)

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 65fe65ba03c2..4e9bd7b589b1 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -290,11 +290,9 @@ static long hist_time(unsigned long htime)
}

static void he_stat__add_period(struct he_stat *he_stat, u64 period,
- u64 weight, u64 ins_lat, u64 p_stage_cyc)
+ u64 ins_lat, u64 p_stage_cyc)
{
-
he_stat->period += period;
- he_stat->weight += weight;
he_stat->nr_events += 1;
he_stat->ins_lat += ins_lat;
he_stat->p_stage_cyc += p_stage_cyc;
@@ -308,9 +306,8 @@ static void he_stat__add_stat(struct he_stat *dest, struct he_stat *src)
dest->period_guest_sys += src->period_guest_sys;
dest->period_guest_us += src->period_guest_us;
dest->nr_events += src->nr_events;
- dest->weight += src->weight;
dest->ins_lat += src->ins_lat;
- dest->p_stage_cyc += src->p_stage_cyc;
+ dest->p_stage_cyc += src->p_stage_cyc;
}

static void he_stat__decay(struct he_stat *he_stat)
@@ -598,7 +595,6 @@ static struct hist_entry *hists__findnew_entry(struct hists *hists,
struct hist_entry *he;
int64_t cmp;
u64 period = entry->stat.period;
- u64 weight = entry->stat.weight;
u64 ins_lat = entry->stat.ins_lat;
u64 p_stage_cyc = entry->stat.p_stage_cyc;
bool leftmost = true;
@@ -619,11 +615,11 @@ static struct hist_entry *hists__findnew_entry(struct hists *hists,

if (!cmp) {
if (sample_self) {
- he_stat__add_period(&he->stat, period, weight, ins_lat, p_stage_cyc);
+ he_stat__add_period(&he->stat, period, ins_lat, p_stage_cyc);
hist_entry__add_callchain_period(he, period);
}
if (symbol_conf.cumulate_callchain)
- he_stat__add_period(he->stat_acc, period, weight, ins_lat, p_stage_cyc);
+ he_stat__add_period(he->stat_acc, period, ins_lat, p_stage_cyc);

/*
* This mem info was allocated from sample__resolve_mem
@@ -733,7 +729,6 @@ __hists__add_entry(struct hists *hists,
.stat = {
.nr_events = 1,
.period = sample->period,
- .weight = sample->weight,
.ins_lat = sample->ins_lat,
.p_stage_cyc = sample->p_stage_cyc,
},
@@ -748,6 +743,7 @@ __hists__add_entry(struct hists *hists,
.raw_size = sample->raw_size,
.ops = ops,
.time = hist_time(sample->time),
+ .weight = sample->weight,
}, *he = hists__findnew_entry(hists, &entry, al, sample_self);

if (!hists->has_callchains && he && he->callchain_size != 0)
diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
index 568a88c001c6..903f34fff27e 100644
--- a/tools/perf/util/sort.c
+++ b/tools/perf/util/sort.c
@@ -1325,45 +1325,35 @@ struct sort_entry sort_mispredict = {
.se_width_idx = HISTC_MISPREDICT,
};

-static u64 he_weight(struct hist_entry *he)
-{
- return he->stat.nr_events ? he->stat.weight / he->stat.nr_events : 0;
-}
-
static int64_t
-sort__local_weight_cmp(struct hist_entry *left, struct hist_entry *right)
+sort__weight_cmp(struct hist_entry *left, struct hist_entry *right)
{
- return he_weight(left) - he_weight(right);
+ return left->weight - right->weight;
}

static int hist_entry__local_weight_snprintf(struct hist_entry *he, char *bf,
size_t size, unsigned int width)
{
- return repsep_snprintf(bf, size, "%-*llu", width, he_weight(he));
+ return repsep_snprintf(bf, size, "%-*llu", width, he->weight);
}

struct sort_entry sort_local_weight = {
.se_header = "Local Weight",
- .se_cmp = sort__local_weight_cmp,
+ .se_cmp = sort__weight_cmp,
.se_snprintf = hist_entry__local_weight_snprintf,
.se_width_idx = HISTC_LOCAL_WEIGHT,
};

-static int64_t
-sort__global_weight_cmp(struct hist_entry *left, struct hist_entry *right)
-{
- return left->stat.weight - right->stat.weight;
-}
-
static int hist_entry__global_weight_snprintf(struct hist_entry *he, char *bf,
size_t size, unsigned int width)
{
- return repsep_snprintf(bf, size, "%-*llu", width, he->stat.weight);
+ return repsep_snprintf(bf, size, "%-*llu", width,
+ he->weight * he->stat.nr_events);
}

struct sort_entry sort_global_weight = {
.se_header = "Weight",
- .se_cmp = sort__global_weight_cmp,
+ .se_cmp = sort__weight_cmp,
.se_snprintf = hist_entry__global_weight_snprintf,
.se_width_idx = HISTC_GLOBAL_WEIGHT,
};
diff --git a/tools/perf/util/sort.h b/tools/perf/util/sort.h
index b67c469aba79..e18b79916f63 100644
--- a/tools/perf/util/sort.h
+++ b/tools/perf/util/sort.h
@@ -49,7 +49,6 @@ struct he_stat {
u64 period_us;
u64 period_guest_sys;
u64 period_guest_us;
- u64 weight;
u64 ins_lat;
u64 p_stage_cyc;
u32 nr_events;
@@ -109,6 +108,7 @@ struct hist_entry {
s32 socket;
s32 cpu;
u64 code_page_size;
+ u64 weight;
u8 cpumode;
u8 depth;

--
2.34.0.rc0.344.g81b53c2807-goog
\
 
 \ /
  Last update: 2021-11-05 23:57    [W:0.126 / U:0.532 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site