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Message-ID: <CACT4Y+ZZhPZMtDdkShhJ5qZqG4BR9DBpCuWNz_H1wc1eQ0tFRg@mail.gmail.com>
Date: Wed, 29 Jan 2025 07:55:55 +0100
From: Dmitry Vyukov <dvyukov@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: irogers@...gle.com, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org, Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH v3 5/7] perf report: Add latency output field
On Wed, 29 Jan 2025 at 05:56, Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Mon, Jan 27, 2025 at 10:58:52AM +0100, Dmitry Vyukov wrote:
> > Latency output field is similar to overhead, but represents overhead for
> > latency rather than CPU consumption. It's re-scaled from overhead by dividing
> > weight by the current parallelism level at the time of the sample.
> > It effectively models profiling with 1 sample taken per unit of wall-clock
> > time rather than unit of CPU time.
> >
> > Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> > Cc: Ian Rogers <irogers@...gle.com>
> > Cc: linux-perf-users@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > ---
> > tools/perf/ui/browsers/hists.c | 27 ++++++++++------
> > tools/perf/ui/hist.c | 29 ++++++++++-------
> > tools/perf/util/addr_location.h | 2 ++
> > tools/perf/util/event.c | 6 ++++
> > tools/perf/util/events_stats.h | 2 ++
> > tools/perf/util/hist.c | 55 ++++++++++++++++++++++++---------
> > tools/perf/util/hist.h | 12 +++++++
> > tools/perf/util/sort.c | 2 ++
> > 8 files changed, 100 insertions(+), 35 deletions(-)
> >
> > diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> > index 49ba82bf33918..35c10509b797f 100644
> > --- a/tools/perf/ui/browsers/hists.c
> > +++ b/tools/perf/ui/browsers/hists.c
> > @@ -1226,7 +1226,7 @@ int __hpp__slsmg_color_printf(struct perf_hpp *hpp, const char *fmt, ...)
> > return ret;
> > }
> >
> > -#define __HPP_COLOR_PERCENT_FN(_type, _field) \
> > +#define __HPP_COLOR_PERCENT_FN(_type, _field, _fmttype) \
> > static u64 __hpp_get_##_field(struct hist_entry *he) \
> > { \
> > return he->stat._field; \
> > @@ -1238,10 +1238,10 @@ hist_browser__hpp_color_##_type(struct perf_hpp_fmt *fmt, \
> > struct hist_entry *he) \
> > { \
> > return hpp__fmt(fmt, hpp, he, __hpp_get_##_field, " %*.2f%%", \
> > - __hpp__slsmg_color_printf, true); \
> > + __hpp__slsmg_color_printf, _fmttype); \
> > }
> >
> > -#define __HPP_COLOR_ACC_PERCENT_FN(_type, _field) \
> > +#define __HPP_COLOR_ACC_PERCENT_FN(_type, _field, _fmttype) \
> > static u64 __hpp_get_acc_##_field(struct hist_entry *he) \
> > { \
> > return he->stat_acc->_field; \
> > @@ -1262,15 +1262,18 @@ hist_browser__hpp_color_##_type(struct perf_hpp_fmt *fmt, \
> > return ret; \
> > } \
> > return hpp__fmt(fmt, hpp, he, __hpp_get_acc_##_field, \
> > - " %*.2f%%", __hpp__slsmg_color_printf, true); \
> > + " %*.2f%%", __hpp__slsmg_color_printf, \
> > + _fmttype); \
> > }
> >
> > -__HPP_COLOR_PERCENT_FN(overhead, period)
> > -__HPP_COLOR_PERCENT_FN(overhead_sys, period_sys)
> > -__HPP_COLOR_PERCENT_FN(overhead_us, period_us)
> > -__HPP_COLOR_PERCENT_FN(overhead_guest_sys, period_guest_sys)
> > -__HPP_COLOR_PERCENT_FN(overhead_guest_us, period_guest_us)
> > -__HPP_COLOR_ACC_PERCENT_FN(overhead_acc, period)
> > +__HPP_COLOR_PERCENT_FN(overhead, period, PERF_HPP_FMT_TYPE__PERCENT)
> > +__HPP_COLOR_PERCENT_FN(latency, latency, PERF_HPP_FMT_TYPE__LATENCY)
> > +__HPP_COLOR_PERCENT_FN(overhead_sys, period_sys, PERF_HPP_FMT_TYPE__PERCENT)
> > +__HPP_COLOR_PERCENT_FN(overhead_us, period_us, PERF_HPP_FMT_TYPE__PERCENT)
> > +__HPP_COLOR_PERCENT_FN(overhead_guest_sys, period_guest_sys, PERF_HPP_FMT_TYPE__PERCENT)
> > +__HPP_COLOR_PERCENT_FN(overhead_guest_us, period_guest_us, PERF_HPP_FMT_TYPE__PERCENT)
> > +__HPP_COLOR_ACC_PERCENT_FN(overhead_acc, period, PERF_HPP_FMT_TYPE__PERCENT)
> > +__HPP_COLOR_ACC_PERCENT_FN(latency_acc, latency, PERF_HPP_FMT_TYPE__LATENCY)
> >
> > #undef __HPP_COLOR_PERCENT_FN
> > #undef __HPP_COLOR_ACC_PERCENT_FN
> > @@ -1279,6 +1282,8 @@ void hist_browser__init_hpp(void)
> > {
> > perf_hpp__format[PERF_HPP__OVERHEAD].color =
> > hist_browser__hpp_color_overhead;
> > + perf_hpp__format[PERF_HPP__LATENCY].color =
> > + hist_browser__hpp_color_latency;
> > perf_hpp__format[PERF_HPP__OVERHEAD_SYS].color =
> > hist_browser__hpp_color_overhead_sys;
> > perf_hpp__format[PERF_HPP__OVERHEAD_US].color =
> > @@ -1289,6 +1294,8 @@ void hist_browser__init_hpp(void)
> > hist_browser__hpp_color_overhead_guest_us;
> > perf_hpp__format[PERF_HPP__OVERHEAD_ACC].color =
> > hist_browser__hpp_color_overhead_acc;
> > + perf_hpp__format[PERF_HPP__LATENCY_ACC].color =
> > + hist_browser__hpp_color_latency_acc;
> >
> > res_sample_init();
> > }
> > diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
> > index 34fda1d5eccb4..22e31d835301e 100644
> > --- a/tools/perf/ui/hist.c
> > +++ b/tools/perf/ui/hist.c
> > @@ -27,9 +27,10 @@ static int __hpp__fmt_print(struct perf_hpp *hpp, struct hists *hists, u64 val,
> > int nr_samples, const char *fmt, int len,
> > hpp_snprint_fn print_fn, enum perf_hpp_fmt_type fmtype)
> > {
> > - if (fmtype == PERF_HPP_FMT_TYPE__PERCENT) {
> > + if (fmtype == PERF_HPP_FMT_TYPE__PERCENT || fmtype == PERF_HPP_FMT_TYPE__LATENCY) {
> > double percent = 0.0;
> > - u64 total = hists__total_period(hists);
> > + u64 total = fmtype == PERF_HPP_FMT_TYPE__PERCENT ? hists__total_period(hists) :
> > + hists__total_latency(hists);
> >
> > if (total)
> > percent = 100.0 * val / total;
> > @@ -128,7 +129,7 @@ int hpp__fmt(struct perf_hpp_fmt *fmt, struct perf_hpp *hpp,
> > print_fn, fmtype);
> > }
> >
> > - if (fmtype == PERF_HPP_FMT_TYPE__PERCENT)
> > + if (fmtype == PERF_HPP_FMT_TYPE__PERCENT || fmtype == PERF_HPP_FMT_TYPE__LATENCY)
> > len -= 2; /* 2 for a space and a % sign */
> > else
> > len -= 1;
> > @@ -472,11 +473,13 @@ __HPP_ENTRY_AVERAGE_FN(_type, _field) \
> > __HPP_SORT_AVERAGE_FN(_type, _field)
> >
> > HPP_PERCENT_FNS(overhead, period)
> > +HPP_PERCENT_FNS(latency, latency)
> > HPP_PERCENT_FNS(overhead_sys, period_sys)
> > HPP_PERCENT_FNS(overhead_us, period_us)
> > HPP_PERCENT_FNS(overhead_guest_sys, period_guest_sys)
> > HPP_PERCENT_FNS(overhead_guest_us, period_guest_us)
> > HPP_PERCENT_ACC_FNS(overhead_acc, period)
> > +HPP_PERCENT_ACC_FNS(latency_acc, latency)
> >
> > HPP_RAW_FNS(samples, nr_events)
> > HPP_RAW_FNS(period, period)
> > @@ -548,11 +551,13 @@ static bool hpp__equal(struct perf_hpp_fmt *a, struct perf_hpp_fmt *b)
> >
> > struct perf_hpp_fmt perf_hpp__format[] = {
> > HPP__COLOR_PRINT_FNS("Overhead", overhead, OVERHEAD),
> > + HPP__COLOR_PRINT_FNS("Latency", latency, LATENCY),
> > HPP__COLOR_PRINT_FNS("sys", overhead_sys, OVERHEAD_SYS),
> > HPP__COLOR_PRINT_FNS("usr", overhead_us, OVERHEAD_US),
> > HPP__COLOR_PRINT_FNS("guest sys", overhead_guest_sys, OVERHEAD_GUEST_SYS),
> > HPP__COLOR_PRINT_FNS("guest usr", overhead_guest_us, OVERHEAD_GUEST_US),
> > HPP__COLOR_ACC_PRINT_FNS("Children", overhead_acc, OVERHEAD_ACC),
> > + HPP__COLOR_ACC_PRINT_FNS("Latency", latency_acc, LATENCY_ACC),
>
> Hmm.. two latency fields have the same name. Maybe better to
> distinguish them but "Children Latency" or "Total Latency" would be
> too long.. :(
>
> I think it's mostly ok since users will see them together with overhead
> columns and it'll give the context ("Children" or "Self"). But it can
> e called with -F or -s option to manually select those columns only.
Yes, the motivation for calling them the same was the column name length.
And, with the default flags it looks reasonable:
Children Latency Self Latency Command
The fields seem to be selected based on the names in sort.c rather
than these names, e.g. I can do:
perf report -F latency_children,overhead_children,latency,overhead,symbol
and get:
Samples: 45K of event 'cycles:Pu', Event count (approx.): 10457486861
Latency Children Latency Overhead Symbol
+ 19.35% 18.69% 0.00% 0.00% [k] 0000000000000000
+ 4.86% 4.21% 4.86% 4.21% [.] htab_find_slot_with_hash
+ 4.15% 4.48% 0.00% 0.00% [.] 0xffffffff9ce012a6
So it seems to be possible to select these columns as needed.
> Thanks,
> Namhyung
>
>
> > HPP__PRINT_FNS("Samples", samples, SAMPLES),
> > HPP__PRINT_FNS("Period", period, PERIOD),
> > HPP__PRINT_FNS("Weight1", weight1, WEIGHT1),
>
> > fmt->free(fmt);
> > }
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