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Message-ID: <e114bf8d2e7b6c0874fffdf8867c954a08772da3.camel@arm.com>
Date: Wed, 29 May 2024 17:47:52 +0000
From: Ben Gainey <Ben.Gainey@....com>
To: "namhyung@...nel.org" <namhyung@...nel.org>
CC: "alexander.shishkin@...ux.intel.com" <alexander.shishkin@...ux.intel.com>,
"peterz@...radead.org" <peterz@...radead.org>, "acme@...nel.org"
<acme@...nel.org>, "mingo@...hat.com" <mingo@...hat.com>, James Clark
<James.Clark@....com>, "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
"irogers@...gle.com" <irogers@...gle.com>, "jolsa@...nel.org"
<jolsa@...nel.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "linux-perf-users@...r.kernel.org"
<linux-perf-users@...r.kernel.org>, Mark Rutland <Mark.Rutland@....com>
Subject: Re: [PATCH v6 4/4] tools/perf: Allow inherit + PERF_SAMPLE_READ when
opening events
On Mon, 2024-05-27 at 18:47 +0100, Ben Gainey wrote:
> On Thu, 2024-05-23 at 18:41 -0700, Namhyung Kim wrote:
> > On Tue, May 21, 2024 at 6:30 AM Ben Gainey <ben.gainey@....com>
> > wrote:
> > >
> > > The tool will now default to this new mode if the user specifies
> > > a
> > > sampling group when not in system-wide mode, and when --no-
> > > inherit
> > > is not specified.
> > >
> > > This change updates evsel to allow the combination of inherit
> > > and PERF_SAMPLE_READ.
> > >
> > > A fallback is implemented for kernel versions where this feature
> > > is
> > > not
> > > supported.
> >
> > But I'm afraid the test would fail on old kernels. Maybe we need
> > to
> > put it in the selftests.
> >
>
> Sorry, not clear what you mean?
>
> Is the issue that the fallback on older kernels fails, or that the
> "perf test" tests fail?
>
> Thanks
> Ben
Just to follow up, I've rechecked the fallback on an unmodified 6.9.1
kernel with the following:
perf record -vv -e '{cycles,instructions}:S' ls
With an unpatched version of perf running on an unpatched kernel, the
cycles event is opened as:
------------------------------------------------------------
perf_event_attr:
type 0 (PERF_TYPE_HARDWARE)
size 136
config 0 (PERF_COUNT_HW_CPU_CYCLES)
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|READ|ID|PERIOD
read_format ID|GROUP|LOST
disabled 1
exclude_kernel 1
exclude_hv 1
mmap 1
comm 1
freq 1
enable_on_exec 1
task 1
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
bpf_event 1
------------------------------------------------------------
whereas with these patches applied to perf, on an unpatched kernel, the
output is as follows
------------------------------------------------------------
perf_event_attr:
type 0 (PERF_TYPE_HARDWARE)
size 136
config 0 (PERF_COUNT_HW_CPU_CYCLES)
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|READ|ID|PERIOD
read_format ID|GROUP|LOST
disabled 1
inherit 1
exclude_kernel 1
exclude_hv 1
mmap 1
comm 1
freq 1
enable_on_exec 1
task 1
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
bpf_event 1
------------------------------------------------------------
sys_perf_event_open: pid 3442954 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open failed, error -22
Using PERF_SAMPLE_READ / :S modifier is not compatible with
inherit, falling back to no-inherit.
------------------------------------------------------------
perf_event_attr:
type 0 (PERF_TYPE_HARDWARE)
size 136
config 0 (PERF_COUNT_HW_CPU_CYCLES)
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|READ|ID|PERIOD
read_format ID|GROUP|LOST
disabled 1
exclude_kernel 1
exclude_hv 1
mmap 1
comm 1
freq 1
enable_on_exec 1
task 1
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
bpf_event 1
------------------------------------------------------------
The command falls back to the same configuration as was previously
used. The same is true for the instructions event.
`perf test` fails on an unpatched kernel in "15: Setup struct
perf_event_attr" for the test "test-record-group-sampling1" but that is
surely expected for unpatched kernels?
Is there some very-old kernel version where this would be expected to
succeed by accident?
Thanks
Ben
>
>
>
> > Thanks,
> > Namhyung
> >
> > >
> > > Signed-off-by: Ben Gainey <ben.gainey@....com>
> > > ---
> > > tools/perf/tests/attr/README | 2 +
> > > .../tests/attr/test-record-group-sampling | 39 ------------
> > > .../tests/attr/test-record-group-sampling1 | 50
> > > ++++++++++++++++
> > > .../tests/attr/test-record-group-sampling2 | 60
> > > +++++++++++++++++++
> > > tools/perf/tests/attr/test-record-group2 | 9 +--
> > > tools/perf/util/evsel.c | 19 +++++-
> > > tools/perf/util/evsel.h | 1 +
> > > 7 files changed, 135 insertions(+), 45 deletions(-)
> > > delete mode 100644 tools/perf/tests/attr/test-record-group-
> > > sampling
> > > create mode 100644 tools/perf/tests/attr/test-record-group-
> > > sampling1
> > > create mode 100644 tools/perf/tests/attr/test-record-group-
> > > sampling2
> > >
> > > diff --git a/tools/perf/tests/attr/README
> > > b/tools/perf/tests/attr/README
> > > index 4066fec7180a8..67c4ca76b85d5 100644
> > > --- a/tools/perf/tests/attr/README
> > > +++ b/tools/perf/tests/attr/README
> > > @@ -51,6 +51,8 @@ Following tests are defined (with perf
> > > commands):
> > > perf record --call-graph fp kill (test-record-
> > > graph-fp-aarch64)
> > > perf record -e '{cycles,instructions}' kill (test-record-
> > > group1)
> > > perf record -e '{cycles/period=1/,instructions/period=2/}:S'
> > > kill (test-record-group2)
> > > + perf record -e '{cycles,cache-misses}:S' kill (test-record-
> > > group-sampling1)
> > > + perf record -c 10000 -e '{cycles,cache-misses}:S' kill (test-
> > > record-group-sampling2)
> > > perf record -D kill (test-record-no-
> > > delay)
> > > perf record -i kill (test-record-no-
> > > inherit)
> > > perf record -n kill (test-record-no-
> > > samples)
> > > diff --git a/tools/perf/tests/attr/test-record-group-sampling
> > > b/tools/perf/tests/attr/test-record-group-sampling
> > > deleted file mode 100644
> > > index 97e7e64a38f07..0000000000000
> > > --- a/tools/perf/tests/attr/test-record-group-sampling
> > > +++ /dev/null
> > > @@ -1,39 +0,0 @@
> > > -[config]
> > > -command = record
> > > -args = --no-bpf-event -e '{cycles,cache-misses}:S' kill
> > > > /dev/null 2>&1
> > > -ret = 1
> > > -
> > > -[event-1:base-record]
> > > -fd=1
> > > -group_fd=-1
> > > -sample_type=343
> > > -read_format=12|28
> > > -inherit=0
> > > -
> > > -[event-2:base-record]
> > > -fd=2
> > > -group_fd=1
> > > -
> > > -# cache-misses
> > > -type=0
> > > -config=3
> > > -
> > > -# default | PERF_SAMPLE_READ
> > > -sample_type=343
> > > -
> > > -# PERF_FORMAT_ID | PERF_FORMAT_GROUP | PERF_FORMAT_LOST
> > > -read_format=12|28
> > > -task=0
> > > -mmap=0
> > > -comm=0
> > > -enable_on_exec=0
> > > -disabled=0
> > > -
> > > -# inherit is disabled for group sampling
> > > -inherit=0
> > > -
> > > -# sampling disabled
> > > -sample_freq=0
> > > -sample_period=0
> > > -freq=0
> > > -write_backward=0
> > > diff --git a/tools/perf/tests/attr/test-record-group-sampling1
> > > b/tools/perf/tests/attr/test-record-group-sampling1
> > > new file mode 100644
> > > index 0000000000000..9b87306266329
> > > --- /dev/null
> > > +++ b/tools/perf/tests/attr/test-record-group-sampling1
> > > @@ -0,0 +1,50 @@
> > > +[config]
> > > +command = record
> > > +args = --no-bpf-event -e '{cycles,cache-misses}:S' kill
> > > > /dev/null 2>&1
> > > +ret = 1
> > > +
> > > +[event-1:base-record]
> > > +fd=1
> > > +group_fd=-1
> > > +
> > > +# cycles
> > > +type=0
> > > +config=0
> > > +
> > > +# default | PERF_SAMPLE_READ
> > > +sample_type=343
> > > +
> > > +# PERF_FORMAT_ID | PERF_FORMAT_GROUP | PERF_FORMAT_LOST |
> > > PERF_FORMAT_TOTAL_TIME_ENABLED | PERF_FORMAT_TOTAL_TIME_RUNNING
> > > +read_format=28|31
> > > +task=1
> > > +mmap=1
> > > +comm=1
> > > +enable_on_exec=1
> > > +disabled=1
> > > +
> > > +# inherit is enabled for group sampling
> > > +inherit=1
> > > +
> > > +[event-2:base-record]
> > > +fd=2
> > > +group_fd=1
> > > +
> > > +# cache-misses
> > > +type=0
> > > +config=3
> > > +
> > > +# default | PERF_SAMPLE_READ
> > > +sample_type=343
> > > +
> > > +# PERF_FORMAT_ID | PERF_FORMAT_GROUP | PERF_FORMAT_LOST |
> > > PERF_FORMAT_TOTAL_TIME_ENABLED | PERF_FORMAT_TOTAL_TIME_RUNNING
> > > +read_format=28|31
> > > +task=0
> > > +mmap=0
> > > +comm=0
> > > +enable_on_exec=0
> > > +disabled=0
> > > +freq=0
> > > +
> > > +# inherit is enabled for group sampling
> > > +inherit=1
> > > +
> > > diff --git a/tools/perf/tests/attr/test-record-group-sampling2
> > > b/tools/perf/tests/attr/test-record-group-sampling2
> > > new file mode 100644
> > > index 0000000000000..8e29fc13f6668
> > > --- /dev/null
> > > +++ b/tools/perf/tests/attr/test-record-group-sampling2
> > > @@ -0,0 +1,60 @@
> > > +[config]
> > > +command = record
> > > +args = --no-bpf-event -c 10000 -e '{cycles,cache-misses}:S'
> > > kill >/dev/null 2>&1
> > > +ret = 1
> > > +
> > > +[event-1:base-record]
> > > +fd=1
> > > +group_fd=-1
> > > +
> > > +# cycles
> > > +type=0
> > > +config=0
> > > +
> > > +# default | PERF_SAMPLE_READ
> > > +sample_type=87
> > > +
> > > +# PERF_FORMAT_ID | PERF_FORMAT_GROUP | PERF_FORMAT_LOST |
> > > PERF_FORMAT_TOTAL_TIME_ENABLED | PERF_FORMAT_TOTAL_TIME_RUNNING
> > > +read_format=28|31
> > > +task=1
> > > +mmap=1
> > > +comm=1
> > > +enable_on_exec=1
> > > +disabled=1
> > > +
> > > +# inherit is enabled for group sampling
> > > +inherit=1
> > > +
> > > +# sampling disabled
> > > +sample_freq=0
> > > +sample_period=10000
> > > +freq=0
> > > +write_backward=0
> > > +
> > > +[event-2:base-record]
> > > +fd=2
> > > +group_fd=1
> > > +
> > > +# cache-misses
> > > +type=0
> > > +config=3
> > > +
> > > +# default | PERF_SAMPLE_READ
> > > +sample_type=87
> > > +
> > > +# PERF_FORMAT_ID | PERF_FORMAT_GROUP | PERF_FORMAT_LOST |
> > > PERF_FORMAT_TOTAL_TIME_ENABLED | PERF_FORMAT_TOTAL_TIME_RUNNING
> > > +read_format=28|31
> > > +task=0
> > > +mmap=0
> > > +comm=0
> > > +enable_on_exec=0
> > > +disabled=0
> > > +
> > > +# inherit is enabled for group sampling
> > > +inherit=1
> > > +
> > > +# sampling disabled
> > > +sample_freq=0
> > > +sample_period=0
> > > +freq=0
> > > +write_backward=0
> > > diff --git a/tools/perf/tests/attr/test-record-group2
> > > b/tools/perf/tests/attr/test-record-group2
> > > index cebdaa8e64e47..785892a54d9e1 100644
> > > --- a/tools/perf/tests/attr/test-record-group2
> > > +++ b/tools/perf/tests/attr/test-record-group2
> > > @@ -9,8 +9,9 @@ group_fd=-1
> > > config=0|1
> > > sample_period=1234000
> > > sample_type=87
> > > -read_format=12|28
> > > -inherit=0
> > > +read_format=28|31
> > > +disabled=1
> > > +inherit=1
> > > freq=0
> > >
> > > [event-2:base-record]
> > > @@ -19,9 +20,9 @@ group_fd=1
> > > config=0|1
> > > sample_period=6789000
> > > sample_type=87
> > > -read_format=12|28
> > > +read_format=28|31
> > > disabled=0
> > > -inherit=0
> > > +inherit=1
> > > mmap=0
> > > comm=0
> > > freq=0
> > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > > index 3536404e9447b..557d409c53d6c 100644
> > > --- a/tools/perf/util/evsel.c
> > > +++ b/tools/perf/util/evsel.c
> > > @@ -1156,7 +1156,15 @@ void evsel__config(struct evsel *evsel,
> > > struct record_opts *opts,
> > > */
> > > if (leader->core.nr_members > 1) {
> > > attr->read_format |= PERF_FORMAT_GROUP;
> > > - attr->inherit = 0;
> > > + }
> > > +
> > > + /*
> > > + * Inherit + SAMPLE_READ requires SAMPLE_TID in
> > > the
> > > read_format
> > > + */
> > > + if (attr->inherit) {
> > > + evsel__set_sample_bit(evsel, TID);
> > > + evsel->core.attr.read_format |=
> > > + PERF_FORMAT_ID;
> > > }
> > > }
> > >
> > > @@ -1832,6 +1840,8 @@ static int __evsel__prepare_open(struct
> > > evsel
> > > *evsel, struct perf_cpu_map *cpus,
> > >
> > > static void evsel__disable_missing_features(struct evsel *evsel)
> > > {
> > > + if (perf_missing_features.inherit_sample_read)
> > > + evsel->core.attr.inherit = 0;
> > > if (perf_missing_features.branch_counters)
> > > evsel->core.attr.branch_sample_type &=
> > > ~PERF_SAMPLE_BRANCH_COUNTERS;
> > > if (perf_missing_features.read_lost)
> > > @@ -1887,7 +1897,12 @@ bool evsel__detect_missing_features(struct
> > > evsel *evsel)
> > > * Must probe features in the order they were added to
> > > the
> > > * perf_event_attr interface.
> > > */
> > > - if (!perf_missing_features.branch_counters &&
> > > + if (!perf_missing_features.inherit_sample_read &&
> > > + evsel->core.attr.inherit && (evsel-
> > > > core.attr.sample_type & PERF_SAMPLE_READ)) {
> > > + perf_missing_features.inherit_sample_read = true;
> > > + pr_debug2("Using PERF_SAMPLE_READ / :S modifier
> > > is
> > > not compatible with inherit, falling back to no-inherit.\n");
> > > + return true;
> > > + } else if (!perf_missing_features.branch_counters &&
> > > (evsel->core.attr.branch_sample_type &
> > > PERF_SAMPLE_BRANCH_COUNTERS)) {
> > > perf_missing_features.branch_counters = true;
> > > pr_debug2("switching off branch counters
> > > support\n");
> > > diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> > > index 517cff431de20..21b8b7e70e75e 100644
> > > --- a/tools/perf/util/evsel.h
> > > +++ b/tools/perf/util/evsel.h
> > > @@ -192,6 +192,7 @@ struct perf_missing_features {
> > > bool weight_struct;
> > > bool read_lost;
> > > bool branch_counters;
> > > + bool inherit_sample_read;
> > > };
> > >
> > > extern struct perf_missing_features perf_missing_features;
> > > --
> > > 2.45.1
> > >
>
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