Messages in this thread Patch in this message | | | From | Song Liu <> | Subject | Re: [PATCH v2 0/3] perf-stat: share hardware PMCs with BPF | Date | Fri, 19 Mar 2021 16:14:42 +0000 |
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> On Mar 19, 2021, at 8:58 AM, Namhyung Kim <namhyung@kernel.org> wrote: > > Hi Arnaldo, > > On Sat, Mar 20, 2021 at 12:35 AM Arnaldo Carvalho de Melo > <acme@kernel.org> wrote: >> >> Em Fri, Mar 19, 2021 at 09:54:59AM +0900, Namhyung Kim escreveu: >>> On Fri, Mar 19, 2021 at 9:22 AM Song Liu <songliubraving@fb.com> wrote: >>>>> On Mar 18, 2021, at 5:09 PM, Arnaldo <arnaldo.melo@gmail.com> wrote: >>>>> On March 18, 2021 6:14:34 PM GMT-03:00, Jiri Olsa <jolsa@redhat.com> wrote: >>>>>> On Thu, Mar 18, 2021 at 03:52:51AM +0000, Song Liu wrote: >>>>>>> perf stat -C 1,3,5 107.063 [sec] >>>>>>> perf stat -C 1,3,5 --bpf-counters 106.406 [sec] >> >>>>>> I can't see why it's actualy faster than normal perf ;-) >>>>>> would be worth to find out >> >>>>> Isn't this all about contended cases? >> >>>> Yeah, the normal perf is doing time multiplexing; while --bpf-counters >>>> doesn't need it. >> >>> Yep, so for uncontended cases, normal perf should be the same as the >>> baseline (faster than the bperf). But for contended cases, the bperf >>> works faster. >> >> The difference should be small enough that for people that use this in a >> machine where contention happens most of the time, setting a >> ~/.perfconfig to use it by default should be advantageous, i.e. no need >> to use --bpf-counters on the command line all the time. >> >> So, Namhyung, can I take that as an Acked-by or a Reviewed-by? I'll take >> a look again now but I want to have this merged on perf/core so that I >> can work on a new BPF SKEL to use this: > > I have a concern for the per cpu target, but it can be done later, so > > Acked-by: Namhyung Kim <namhyung@kernel.org> > >> >> https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/log/?h=tmp.bpf/bpf_perf_enable > > Interesting! Actually I was thinking about the similar too. :)
Hi Namhyung, Jiri, and Arnaldo,
Thanks a lot for your kind review.
Here is updated 3/3, where we use perf-bench instead of stressapptest.
Thanks, Song
From cc79d161be9c9d24198f7e35b50058a6e15076fd Mon Sep 17 00:00:00 2001 From: Song Liu <songliubraving@fb.com> Date: Tue, 16 Mar 2021 00:19:53 -0700 Subject: [PATCH v3 3/3] perf-test: add a test for perf-stat --bpf-counters option
Add a test to compare the output of perf-stat with and without option --bpf-counters. If the difference is more than 10%, the test is considered as failed.
Signed-off-by: Song Liu <songliubraving@fb.com> --- tools/perf/tests/shell/stat_bpf_counters.sh | 31 +++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100755 tools/perf/tests/shell/stat_bpf_counters.sh
diff --git a/tools/perf/tests/shell/stat_bpf_counters.sh b/tools/perf/tests/shell/stat_bpf_counters.sh new file mode 100755 index 0000000000000..7aabf177ce8d1 --- /dev/null +++ b/tools/perf/tests/shell/stat_bpf_counters.sh @@ -0,0 +1,31 @@ +#!/bin/sh +# perf stat --bpf-counters test +# SPDX-License-Identifier: GPL-2.0 + +set -e + +# check whether $2 is within +/- 10% of $1 +compare_number() +{ + first_num=$1 + second_num=$2 + + # upper bound is first_num * 110% + upper=$(( $first_num + $first_num / 10 )) + # lower bound is first_num * 90% + lower=$(( $first_num - $first_num / 10 )) + + if [ $second_num -gt $upper ] || [ $second_num -lt $lower ]; then + echo "The difference between $first_num and $second_num are greater than 10%." + exit 1 + fi +} + +# skip if --bpf-counters is not supported +perf stat --bpf-counters true > /dev/null 2>&1 || exit 2 + +base_cycles=$(perf stat --no-big-num -e cycles -- perf bench sched messaging -g 1 -l 100 -t 2>&1 | awk '/cycles/ {print $1}') +bpf_cycles=$(perf stat --no-big-num --bpf-counters -e cycles -- perf bench sched messaging -g 1 -l 100 -t 2>&1 | awk '/cycles/ {print $1}') + +compare_number $base_cycles $bpf_cycles +exit 0 -- 2.30.2
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