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Mon, 09 Nov 2026 12:02:18 -0800 (PST) Received: from ehlo.thunderbird.net ([2804:2bf0:60e7:ae00:175b:6568:be30:fd38]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-37520cfe07dsm556671eec.20.2026.11.09.12.02.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Nov 2026 12:02:17 -0800 (PST) Date: Mon, 09 Nov 2026 17:02:11 -0300 From: Arnaldo Melo To: linux-perf-users@vger.kernel.org, Ian Rogers , Samuel Wu CC: Lalit Maganti , acme@kernel.org, namhyung@kernel.org, james.clark@linaro.org, adrian.hunter@intel.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf python: Accept events larger than union perf_event User-Agent: Thunderbird for Android In-Reply-To: References: <20261018074528.974953-1-lalitmaganti@gmail.com> Message-ID: X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On November 9, 2026 3:27:56 PM GMT-03:00, Ian Rogers wrote: >On Mon, Nov 9, 2026 at 9:58=E2=80=AFAM Samuel Wu = wrote: >> >> On Sun, Oct 18, 2026 at 12:45=E2=80=AFAM Lalit Maganti wrote: >> > >> > Samples recorded with --call-graph dwarf carry a copy of the user sta= ck >> > and are larger than union perf_event, so session=2Eprocess_events() >> > fails on the first one: >> > >> > $ perf record --call-graph dwarf -- =2E/workload >> > $ python3 tools/perf/python/stackcollapse=2Epy >> > =2E=2E=2E >> > TypeError: Unexpected event size: 4168 < 8424 >> > >> > This makes all the standalone scripts unusable on such recordings=2E >> > >> > pyrf_event__new() rejects events larger than union perf_event, which >> > guarded the copy into the union that pyrf_event used to embed=2E Sinc= e >> > commit 2c672ffdad4b ("perf python: Lazily copy events and samples fro= m >> > process_events") the event is borrowed, or copied to a buffer of >> > header=2Esize bytes when a callback keeps it, so nothing depends on t= he >> > event fitting in the union any more=2E Remove the check=2E >> > >> > With this, stackcollapse=2Epy and flamegraph=2Epy process a DWARF rec= ording >> > of a two-thread workload, with the same per-symbol sample counts as >> > perf script, also when the callback keeps the events after returning= =2E >> > >> > Assisted-by: LLM >> > Signed-off-by: Lalit Maganti > >Probably worth having: > >Fixes: 2c672ffdad4b ("perf python: Lazily copy events and samples from >process_events") > >Reviewed-by: Ian Rogers I'll pick it for v7=2E4, Thanks, - Arnaldo=20 > >Thanks, >Ian > >> > --- >> > tools/perf/util/python=2Ec | 5 ----- >> > 1 file changed, 5 deletions(-) >> > >> > diff --git a/tools/perf/util/python=2Ec b/tools/perf/util/python=2Ec >> > index 60dbe2dad5eb=2E=2E8b4b2f3d0926 100644 >> > --- a/tools/perf/util/python=2Ec >> > +++ b/tools/perf/util/python=2Ec >> > @@ -1792,11 +1792,6 @@ static PyObject *pyrf_event__new(const union p= erf_event *event, struct evsel *ev >> > event->header=2Esize, event->head= er=2Etype); >> > } >> > >> > - if (event->header=2Esize > sizeof(union perf_event)) { >> > - return PyErr_Format(PyExc_TypeError, "Unexpected even= t size: %zu < %u", >> > - sizeof(union perf_event), event->= header=2Esize); >> > - } >> > - >> > pevent =3D PyObject_New(struct pyrf_event, pyrf_event__type[e= vent->header=2Etype]); >> > if (pevent =3D=3D NULL) >> > return PyErr_NoMemory(); >> > >> > base-commit: 1c90f0a3c8a1c4e38f9edd97af9e20848805a7fb >> > -- >> > 2=2E56=2E0 >> > >> >> Reviewed-by: Samuel Wu > - Arnaldo