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Message-ID: <ZvMfVe1VXwhCIOB9@google.com> Date: Tue, 24 Sep 2024 13:21:41 -0700 From: Namhyung Kim <namhyung@...nel.org> To: James Clark <james.clark@...aro.org> Cc: "Liang, Kan" <kan.liang@...ux.intel.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Ian Rogers <irogers@...gle.com>, Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org, Ravi Bangoria <ravi.bangoria@....com>, Mark Rutland <mark.rutland@....com>, James Clark <james.clark@....com>, Kajol Jain <kjain@...ux.ibm.com>, Thomas Richter <tmricht@...ux.ibm.com>, Atish Patra <atishp@...shpatra.org>, Palmer Dabbelt <palmer@...osinc.com>, Mingwei Zhang <mizhang@...gle.com> Subject: Re: [PATCH 04/10] perf stat: Add --exclude-guest option Hello, On Mon, Sep 23, 2024 at 09:47:17AM +0100, James Clark wrote: > > > On 06/09/2024 3:33 pm, Liang, Kan wrote: > > > > > > On 2024-09-05 4:24 p.m., Namhyung Kim wrote: > > > This option is to support the old behavior of setting exclude_guest by > > > default. Now it doesn't set the bit so users want the old behavior can > > > use this option. > > > > > > $ perf stat true > > > > > > Performance counter stats for 'true': > > > > > > 0.86 msec task-clock:u # 0.443 CPUs utilized > > > 0 context-switches:u # 0.000 /sec > > > 0 cpu-migrations:u # 0.000 /sec > > > 49 page-faults:u # 56.889 K/sec > > > ... > > > > > > $ perf stat --exclude-guest true > > > > > > Performance counter stats for 'true': > > > > > > 0.79 msec task-clock:Hu # 0.490 CPUs utilized > > > 0 context-switches:Hu # 0.000 /sec > > > 0 cpu-migrations:Hu # 0.000 /sec > > > 49 page-faults:Hu # 62.078 K/sec > > > ... > > > > > > Signed-off-by: Namhyung Kim <namhyung@...nel.org> > > > --- > > > tools/perf/Documentation/perf-stat.txt | 7 +++++++ > > > tools/perf/builtin-stat.c | 2 ++ > > > 2 files changed, 9 insertions(+) > > > > > > diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt > > > index 2bc06367248691dd..d28d8370a856598f 100644 > > > --- a/tools/perf/Documentation/perf-stat.txt > > > +++ b/tools/perf/Documentation/perf-stat.txt > > > @@ -382,6 +382,13 @@ color the metric's computed value. > > > Don't print output, warnings or messages. This is useful with perf stat > > > record below to only write data to the perf.data file. > > > +--exclude-guest:: > > > +Don't count event in the guest mode. It was the old behavior but the > > > +default is changed to count guest events also. Use this option if you > > > +want the old behavior (host only). Note that this option needs to be > > > +before other events in case you added -e/--event option in the command > > > +line. > > > > I'm not sure if we really need this option. I think it may bring more > > trouble than what we get. > > > > The name of the "--exclude-guest" sounds like a replacement of the event > > modifier "H". But in fact, it's not. It should only affect the default. > > It doesn't set the "H" for any events. Well I think it's tricky but it'd set "H" modifier events after the option. But I have to agree that it can bring more troubles. > > > > Except for the perf kvm user, I don't think there are many users which > > care the exclude_guest. The behavior of the perf kvm is not changed. So > > the option seems not that important. If we really want an option to > > restore the old behavior, it's better to choose a better name and update > > the description. Personally I don't want to this option but just worried if there's a case where exclude_guest is preferred. > > Do we not want to keep exclude_guest for record, but remove it for stat? What I really want is to synchronize record and stat behavior in terms of the default exclusion mode. If everyone is fine, I'd like to remove exclude_guest from the default and set it only if needed (through the fallback) like we do for exclude_kernel. > > Because in record the addresses of guest samples don't make sense without > extra work, but for stat you might want to see an overview of the whole > system. I think it depends on the use case and (power) users should know about their environment and requirement. The concern is what's the reasonable default, but I think it should be the same both in perf record and stat at least. > > For Coresight tracing and SPE we would want to keep exclude_guest, otherwise > you generate a load of extra trace that you can't make use of. Say you were > doing PGO on your host you wouldn't be recompiling anything the guests were > running. For the specific use case, I think we can guide users to add "H" modifier (I guess it's not the default event for perf record). Maybe we can consider per-PMU default attributes. > > If we do change the defaults isn't ':H' already enough to go back to the old > behavior? I'm wondering why we need an argument when all the other exclude > rules are done with the letter modifiers? I'm not sure I follow this. But maybe we don't need this option at all. We can add ":H" for every event but I'm too lazy to add them to all the default events in perf data. :) Thanks, Namhyung > > > + > > > STAT RECORD > > > ----------- > > > Stores stat data into perf data file. > > > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > > > index d8315dae930184ba..4d47675af5cc3094 100644 > > > --- a/tools/perf/builtin-stat.c > > > +++ b/tools/perf/builtin-stat.c > > > @@ -2491,6 +2491,8 @@ int cmd_stat(int argc, const char **argv) > > > OPT_BOOLEAN_FLAG(0, "all-user", &stat_config.all_user, > > > "Configure all used events to run in user space.", > > > PARSE_OPT_EXCLUSIVE), > > > + OPT_BOOLEAN(0, "exclude-guest", &exclude_HG_default, > > > + "Don't count events in the guest mode"), > > > OPT_BOOLEAN(0, "percore-show-thread", &stat_config.percore_show_thread, > > > "Use with 'percore' event qualifier to show the event " > > > "counts of one hardware thread by sum up total hardware " >
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