Re: [PATCH 1/4] perf tools: Don't set attr.exclude_guest by default

From: Namhyung Kim
Date: Mon Sep 02 2024 - 13:39:07 EST

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On Mon, Sep 02, 2024 at 10:15:57AM +0100, James Clark wrote:
>
>
> On 02/09/2024 2:46 am, Namhyung Kim wrote:
> > The exclude_guest in the event attribute is to limit profiling in the
> > host environment. But I'm not sure why we want to set it by default
> > cause we don't care about it in most cases and I feel like it just
> > makes new PMU implementation complicated.
> >
> > Of course it's useful for perf kvm command so I added the
> > exclude_GH_default variable to preserve the old behavior for perf kvm
> > and other commands like perf record and stat won't set the exclude bit.
> > This is helpful for AMD IBS case since having exclude_guest bit will
> > clear new feature bit due to the missing feature check logic.
>
> Probably another case where again the real fix would be to add
> /sys/bus/event_source/devices/cpu_core/caps/exclude_guest and then we're
> able to keep the defaults.

Yep, I really need to work on it. But it's another story whether it's
supported and whether it's required.

>
> >
> > $ sysctl kernel.perf_event_paranoid
> > kernel.perf_event_paranoid = 0
> >
> > $ perf record -W -e ibs_op// -vv true 2>&1 | grep switching
> > switching off PERF_FORMAT_LOST support
> > switching off weight struct support
> > switching off bpf_event
> > switching off ksymbol
> > switching off cloexec flag
> > switching off mmap2
> > switching off exclude_guest, exclude_host
> >
> > Maybe Apple M1 users will scream but actually the default event for
> > perf record was converted to "cycles:P" which doesn't set the
> > exclude_guest bit already. So they need to specify the necessary
> > modifier manually like "cycles:PH" and I think it's ok.
>
> I'm reading this to assume that the default record command was always broken
> then? But what about any other command, now isn't just "cycles" also broken
> making it worse?

Hmm.. right. Maybe we can add a detection logic to figure out the
required exclude bits for a PMU at runtime.

Thanks,
Namhyung

>
> See 25412c036:
>
> ...
> (c) The Apple M1/M2 PMU requires that perf_event_attr::exclude_guest
> is set as the hardware PMU does not count while a guest is running
> (but might be extended in future to do so).
> ...
>
> >
> > Intestingly, I found it sets the exclude_bit if "u" modifier is used.
> > I don't know why but it's neither intuitive nor consistent. Let's
> > remove the bit there too.
> >
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: James Clark <james.clark@xxxxxxxxxx>
> > Cc: Ravi Bangoria <ravi.bangoria@xxxxxxx>
> > Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> > ---
> > tools/perf/builtin-kvm.c | 1 +
> > tools/perf/tests/attr/test-record-dummy-C0 | 2 +-
> > tools/perf/tests/parse-events.c | 18 +++++++++---------
> > tools/perf/util/parse-events.c | 2 +-
> > tools/perf/util/util.c | 10 ++++++++--
> > tools/perf/util/util.h | 3 +++
> > 6 files changed, 23 insertions(+), 13 deletions(-)
> >
> > diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
> > index 692267b1b7e8..ca94dd3de04d 100644
> > --- a/tools/perf/builtin-kvm.c
> > +++ b/tools/perf/builtin-kvm.c
> > @@ -2147,6 +2147,7 @@ int cmd_kvm(int argc, const char **argv)
> > "buildid-list", "stat", NULL };
> > const char *kvm_usage[] = { NULL, NULL };
> > + exclude_HG_default = true;
> > perf_host = 0;
> > perf_guest = 1;
> > diff --git a/tools/perf/tests/attr/test-record-dummy-C0 b/tools/perf/tests/attr/test-record-dummy-C0
> > index 576ec48b3aaf..8ce6f0a5df5b 100644
> > --- a/tools/perf/tests/attr/test-record-dummy-C0
> > +++ b/tools/perf/tests/attr/test-record-dummy-C0
> > @@ -37,7 +37,7 @@ precise_ip=0
> > mmap_data=0
> > sample_id_all=1
> > exclude_host=0
> > -exclude_guest=1
> > +exclude_guest=0
> > exclude_callchain_kernel=0
> > exclude_callchain_user=0
> > mmap2=1
> > diff --git a/tools/perf/tests/parse-events.c b/tools/perf/tests/parse-events.c
> > index edc2adcf1bae..9179bf3084c3 100644
> > --- a/tools/perf/tests/parse-events.c
> > +++ b/tools/perf/tests/parse-events.c
> > @@ -932,7 +932,7 @@ static int test__group2(struct evlist *evlist)
> > TEST_ASSERT_VAL("wrong exclude_user", !evsel->core.attr.exclude_user);
> > TEST_ASSERT_VAL("wrong exclude_kernel", !evsel->core.attr.exclude_kernel);
> > TEST_ASSERT_VAL("wrong exclude_hv", evsel->core.attr.exclude_hv);
> > - TEST_ASSERT_VAL("wrong exclude guest", evsel->core.attr.exclude_guest);
> > + TEST_ASSERT_VAL("wrong exclude guest", !evsel->core.attr.exclude_guest);
> > TEST_ASSERT_VAL("wrong exclude host", !evsel->core.attr.exclude_host);
> > TEST_ASSERT_VAL("wrong precise_ip", !evsel->core.attr.precise_ip);
> > TEST_ASSERT_VAL("wrong leader", evsel__is_group_leader(evsel));
> > @@ -947,7 +947,7 @@ static int test__group2(struct evlist *evlist)
> > TEST_ASSERT_VAL("wrong exclude_user", !evsel->core.attr.exclude_user);
> > TEST_ASSERT_VAL("wrong exclude_kernel", evsel->core.attr.exclude_kernel);
> > TEST_ASSERT_VAL("wrong exclude_hv", evsel->core.attr.exclude_hv);
> > - TEST_ASSERT_VAL("wrong exclude guest", evsel->core.attr.exclude_guest);
> > + TEST_ASSERT_VAL("wrong exclude guest", !evsel->core.attr.exclude_guest);
> > TEST_ASSERT_VAL("wrong exclude host", !evsel->core.attr.exclude_host);
> > TEST_ASSERT_VAL("wrong precise_ip", !evsel->core.attr.precise_ip);
> > if (evsel__has_leader(evsel, leader))
> > @@ -1072,7 +1072,7 @@ static int test__group3(struct evlist *evlist __maybe_unused)
> > TEST_ASSERT_VAL("wrong exclude_user", !evsel->core.attr.exclude_user);
> > TEST_ASSERT_VAL("wrong exclude_kernel", evsel->core.attr.exclude_kernel);
> > TEST_ASSERT_VAL("wrong exclude_hv", evsel->core.attr.exclude_hv);
> > - TEST_ASSERT_VAL("wrong exclude guest", evsel->core.attr.exclude_guest);
> > + TEST_ASSERT_VAL("wrong exclude guest", !evsel->core.attr.exclude_guest);
> > TEST_ASSERT_VAL("wrong exclude host", !evsel->core.attr.exclude_host);
> > TEST_ASSERT_VAL("wrong precise_ip", !evsel->core.attr.precise_ip);
> > TEST_ASSERT_VAL("wrong leader", evsel__is_group_leader(evsel));
> > @@ -1222,7 +1222,7 @@ static int test__group5(struct evlist *evlist __maybe_unused)
> > TEST_ASSERT_VAL("wrong exclude_user", !evsel->core.attr.exclude_user);
> > TEST_ASSERT_VAL("wrong exclude_kernel", !evsel->core.attr.exclude_kernel);
> > TEST_ASSERT_VAL("wrong exclude_hv", !evsel->core.attr.exclude_hv);
> > - TEST_ASSERT_VAL("wrong exclude guest", evsel->core.attr.exclude_guest);
> > + TEST_ASSERT_VAL("wrong exclude guest", !evsel->core.attr.exclude_guest);
> > TEST_ASSERT_VAL("wrong exclude host", !evsel->core.attr.exclude_host);
> > TEST_ASSERT_VAL("wrong precise_ip", !evsel->core.attr.precise_ip);
> > TEST_ASSERT_VAL("wrong leader", evsel__is_group_leader(evsel));
> > @@ -1437,7 +1437,7 @@ static int test__leader_sample1(struct evlist *evlist)
> > TEST_ASSERT_VAL("wrong exclude_user", !evsel->core.attr.exclude_user);
> > TEST_ASSERT_VAL("wrong exclude_kernel", !evsel->core.attr.exclude_kernel);
> > TEST_ASSERT_VAL("wrong exclude_hv", !evsel->core.attr.exclude_hv);
> > - TEST_ASSERT_VAL("wrong exclude guest", evsel->core.attr.exclude_guest);
> > + TEST_ASSERT_VAL("wrong exclude guest", !evsel->core.attr.exclude_guest);
> > TEST_ASSERT_VAL("wrong exclude host", !evsel->core.attr.exclude_host);
> > TEST_ASSERT_VAL("wrong precise_ip", !evsel->core.attr.precise_ip);
> > TEST_ASSERT_VAL("wrong group name", !evsel->group_name);
> > @@ -1453,7 +1453,7 @@ static int test__leader_sample1(struct evlist *evlist)
> > TEST_ASSERT_VAL("wrong exclude_user", !evsel->core.attr.exclude_user);
> > TEST_ASSERT_VAL("wrong exclude_kernel", !evsel->core.attr.exclude_kernel);
> > TEST_ASSERT_VAL("wrong exclude_hv", !evsel->core.attr.exclude_hv);
> > - TEST_ASSERT_VAL("wrong exclude guest", evsel->core.attr.exclude_guest);
> > + TEST_ASSERT_VAL("wrong exclude guest", !evsel->core.attr.exclude_guest);
> > TEST_ASSERT_VAL("wrong exclude host", !evsel->core.attr.exclude_host);
> > TEST_ASSERT_VAL("wrong precise_ip", !evsel->core.attr.precise_ip);
> > TEST_ASSERT_VAL("wrong leader", evsel__has_leader(evsel, leader));
> > @@ -1468,7 +1468,7 @@ static int test__leader_sample1(struct evlist *evlist)
> > TEST_ASSERT_VAL("wrong exclude_user", !evsel->core.attr.exclude_user);
> > TEST_ASSERT_VAL("wrong exclude_kernel", !evsel->core.attr.exclude_kernel);
> > TEST_ASSERT_VAL("wrong exclude_hv", !evsel->core.attr.exclude_hv);
> > - TEST_ASSERT_VAL("wrong exclude guest", evsel->core.attr.exclude_guest);
> > + TEST_ASSERT_VAL("wrong exclude guest", !evsel->core.attr.exclude_guest);
> > TEST_ASSERT_VAL("wrong exclude host", !evsel->core.attr.exclude_host);
> > TEST_ASSERT_VAL("wrong precise_ip", !evsel->core.attr.precise_ip);
> > TEST_ASSERT_VAL("wrong group name", !evsel->group_name);
> > @@ -1497,7 +1497,7 @@ static int test__leader_sample2(struct evlist *evlist __maybe_unused)
> > TEST_ASSERT_VAL("wrong exclude_user", !evsel->core.attr.exclude_user);
> > TEST_ASSERT_VAL("wrong exclude_kernel", evsel->core.attr.exclude_kernel);
> > TEST_ASSERT_VAL("wrong exclude_hv", evsel->core.attr.exclude_hv);
> > - TEST_ASSERT_VAL("wrong exclude guest", evsel->core.attr.exclude_guest);
> > + TEST_ASSERT_VAL("wrong exclude guest", !evsel->core.attr.exclude_guest);
> > TEST_ASSERT_VAL("wrong exclude host", !evsel->core.attr.exclude_host);
> > TEST_ASSERT_VAL("wrong precise_ip", !evsel->core.attr.precise_ip);
> > TEST_ASSERT_VAL("wrong group name", !evsel->group_name);
> > @@ -1513,7 +1513,7 @@ static int test__leader_sample2(struct evlist *evlist __maybe_unused)
> > TEST_ASSERT_VAL("wrong exclude_user", !evsel->core.attr.exclude_user);
> > TEST_ASSERT_VAL("wrong exclude_kernel", evsel->core.attr.exclude_kernel);
> > TEST_ASSERT_VAL("wrong exclude_hv", evsel->core.attr.exclude_hv);
> > - TEST_ASSERT_VAL("wrong exclude guest", evsel->core.attr.exclude_guest);
> > + TEST_ASSERT_VAL("wrong exclude guest", !evsel->core.attr.exclude_guest);
> > TEST_ASSERT_VAL("wrong exclude host", !evsel->core.attr.exclude_host);
> > TEST_ASSERT_VAL("wrong precise_ip", !evsel->core.attr.precise_ip);
> > TEST_ASSERT_VAL("wrong group name", !evsel->group_name);
> > diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> > index fab01ba54e34..ab73b3d45f04 100644
> > --- a/tools/perf/util/parse-events.c
> > +++ b/tools/perf/util/parse-events.c
> > @@ -1739,7 +1739,7 @@ static int parse_events__modifier_list(struct parse_events_state *parse_state,
> > if (mod.user) {
> > if (!exclude)
> > exclude = eu = ek = eh = 1;
> > - if (!exclude_GH && !perf_guest)
> > + if (!exclude_GH && !perf_guest && exclude_HG_default)
> > eG = 1;
> > eu = 0;
> > }
> > diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
> > index 9d55a13787ce..7e3159faaa19 100644
> > --- a/tools/perf/util/util.c
> > +++ b/tools/perf/util/util.c
> > @@ -78,17 +78,23 @@ bool sysctl__nmi_watchdog_enabled(void)
> > bool test_attr__enabled;
> > +bool exclude_HG_default;
> > +
> > bool perf_host = true;
> > bool perf_guest = false;
> > void event_attr_init(struct perf_event_attr *attr)
> > {
> > + /* to capture ABI version */
> > + attr->size = sizeof(*attr);
> > +
> > + if (!exclude_HG_default)
> > + return;
> > +
> > if (!perf_host)
> > attr->exclude_host = 1;
> > if (!perf_guest)
> > attr->exclude_guest = 1;
> > - /* to capture ABI version */
> > - attr->size = sizeof(*attr);
> > }
> > int mkdir_p(char *path, mode_t mode)
> > diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
> > index 9966c21aaf04..d33ae883a54f 100644
> > --- a/tools/perf/util/util.h
> > +++ b/tools/perf/util/util.h
> > @@ -21,6 +21,9 @@ extern const char perf_more_info_string[];
> > extern const char *input_name;
> > +/* This will control if perf_{host,guest} will set attr.exclude_{host,guest}. */
> > +extern bool exclude_HG_default;
> > +
> > extern bool perf_host;
> > extern bool perf_guest;

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In reply to: James Clark: "Re: [PATCH 1/4] perf tools: Don't set attr.exclude_guest by default"
Next in thread: Namhyung Kim: "[PATCH 2/4] perf tools: Simplify evsel__add_modifier()"
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