Messages in this thread Patch in this message | | | From | Namhyung Kim <> | Subject | [RFC 1/3] perf tools: Fix weight sort key behavior | Date | Fri, 5 Nov 2021 15:56:15 -0700 |
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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
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