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Mon, 24 Aug 2026 10:10:27 +0000 Message-ID: <823e897f-13c0-4b07-8833-3bbfe37059ca@intel.com> Date: Mon, 24 Aug 2026 13:10:20 +0300 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/5] perf dlfilter: Add non-empty branch stack filter To: Amir Ayupov , , , , "Suzuki K Poulose" , James Clark , "Leo Yan" , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , "Alexander Shishkin" , Jiri Olsa , Ian Rogers , John Garry , "Will Deacon" CC: , Mike Leach , "Jonathan Corbet" , Shuah Khan , "Swapnil Sapkal" References: <58f96797f94467859fec160320a7b9426be8cce7.1787005265.git.aaupov@fb.com> Content-Language: en-US From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo, Business Identity Code: 0357606 - 4, Domiciled in Helsinki In-Reply-To: <58f96797f94467859fec160320a7b9426be8cce7.1787005265.git.aaupov@fb.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: DB9PR05CA0029.eurprd05.prod.outlook.com (2603:10a6:10:1da::34) To IA1PR11MB7198.namprd11.prod.outlook.com (2603:10b6:208:419::15) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA1PR11MB7198:EE_|IA4PR11MB8889:EE_ X-MS-Office365-Filtering-Correlation-Id: 38494c4f-6127-4b14-ac33-08df01c7eb9d X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|376014|1800799024|7416014|921020|6133799003|56012099006|11063799006|10067099003|4143699003|3023799007|18002099003|22082099003; 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Consumers of the resulting perf script output, such > as profile generators for context-sensitive PGO, have no use for those > samples. > > Add an opt-in dlfilter that drops samples whose parsed branch stack is > empty, so users can exclude them without changing default sample > semantics. Build and install it alongside perf's existing dlfilters. > > Assisted-by: Devmate:GPT-5.6 > Signed-off-by: Amir Ayupov > Reviewed-by: James Clark Reviewed-by: Adrian Hunter > --- > tools/perf/Makefile.perf | 1 + > .../dlfilters/dlfilter-nonempty-brstack.c | 26 +++++++++++++++++++ > 2 files changed, 27 insertions(+) > create mode 100644 tools/perf/dlfilters/dlfilter-nonempty-brstack.c > > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf > index 29cfd44c427f3..750bd1cce1287 100644 > --- a/tools/perf/Makefile.perf > +++ b/tools/perf/Makefile.perf > @@ -425,6 +425,7 @@ PROGRAMS += $(OUTPUT)$(LIBJVMTI) > endif > > DLFILTERS := dlfilter-test-api-v0.so dlfilter-test-api-v2.so dlfilter-show-cycles.so > +DLFILTERS += dlfilter-nonempty-brstack.so > DLFILTERS := $(patsubst %,$(OUTPUT)dlfilters/%,$(DLFILTERS)) > > # what 'all' will build and 'install' will install, in perfexecdir > diff --git a/tools/perf/dlfilters/dlfilter-nonempty-brstack.c b/tools/perf/dlfilters/dlfilter-nonempty-brstack.c > new file mode 100644 > index 0000000000000..9e66205b841d5 > --- /dev/null > +++ b/tools/perf/dlfilters/dlfilter-nonempty-brstack.c > @@ -0,0 +1,26 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * dlfilter-nonempty-brstack.c: Filter out samples with no branch stack > + * Copyright (c) 2026, Meta Platforms, Inc. > + */ > +#include > + > +#include > + > +int filter_event(void *data, const struct perf_dlfilter_sample *sample, void *ctx) > +{ > + /* Return 1 to filter out the sample, 0 to keep it */ > + return !sample->brstack_nr; > +} > + > +const char *filter_description(const char **long_description) > +{ > + static char *long_desc = > + "Instruction trace decoders can add branch history to existing " > + "samples, but samples that were recorded while no trace was " > + "being collected get an empty branch stack. Filter those out so " > + "that only samples carrying branch history remain."; > + > + *long_description = long_desc; > + return "Keep only samples with a non-empty branch stack"; > +}