From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E6F8930597C; Tue, 18 Nov 2025 02:41:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763433661; cv=none; b=X4C/EQ2fLSJI0AkKg3nPFWpkpMs65O4z9b5E9C0atP3shoyoJDnHhVahRGx0K/UPJg60bSEXtaPKvkWaWDsChkmfWLyV4TqgnS8e98Ye18yUQF6WEC9MIQ1bprN8wKN2AE/zEQdbGpA0SIIij+iLiOBMjn7rU+tRtTzBY5hRz3c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763433661; c=relaxed/simple; bh=Q62wl5sZGcLb5+Fr+2IFnjR/5GV0RSMjVfTridFArNY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OKljG4LnNwAWRsW+wiwPxDWspyaavU8QL1MeKfEvft/ys9u3qA68neCbZ/hHuoLJAH4xFZ6OXGC2xDcMUZ6wRSXtAxpSn3wwGD4ux2JewLGI9mDDPEwsCJXDk+dwPy4D5QtD8KIAmtaM30mBfsHn+4ZvdIr1ABErvNgZZxZMhRo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ExIXac5u; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ExIXac5u" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A72CCC2BC86; Tue, 18 Nov 2025 02:40:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763433660; bh=Q62wl5sZGcLb5+Fr+2IFnjR/5GV0RSMjVfTridFArNY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ExIXac5uan/kk+heaVqh3AQcw9YzyZFjIgkJpuRcH6qPS9XGFtYF/sfFp/YyDg+91 bFio0c9JMRl9dw0uzB02XbeVG3TrdWZ6fNLw2TsA1VRxSg0yb//9kCHi4jYQ8hZ4Nf iCk0VYq7Bz0egeE2WvM/b8xAWVGm1BZGJnb+uo75EKD0P3BPLguxMKYVmnYb59r/Ow pyInEyp/x8J6ywfoMjWkty6nBiaGunU+ZklezmUcrvTIw4p+nAl7eAWodvAcwj8rNh ka4r8YUXOQCdlM+wAoWrXG45K1sCDNOcZibYVSClCGkiA+GAQyBRzb1ZzcfkTvjNAr agc6RguGNFcHQ== Date: Mon, 17 Nov 2025 18:40:56 -0800 From: Namhyung Kim To: Ian Rogers Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Adrian Hunter , "Dr. David Alan Gilbert" , Yang Li , James Clark , Thomas Falcon , Thomas Richter , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Andi Kleen , Dapeng Mi Subject: Re: [PATCH v4 10/10] perf stat: Add no-affinity flag Message-ID: References: <20251113180517.44096-1-irogers@google.com> <20251113180517.44096-11-irogers@google.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20251113180517.44096-11-irogers@google.com> On Thu, Nov 13, 2025 at 10:05:16AM -0800, Ian Rogers wrote: > Add flag that disables affinity behavior. Using sched_setaffinity to > place a perf thread on a CPU can avoid certain interprocessor > interrupts but may introduce a delay due to the scheduling, > particularly on loaded machines. Add a command line option to disable > the behavior. This behavior is less present in other tools like `perf > record`, as it uses a ring buffer and doesn't make repeated system > calls. > > Signed-off-by: Ian Rogers > --- > tools/perf/Documentation/perf-stat.txt | 4 ++++ > tools/perf/builtin-stat.c | 6 ++++++ > tools/perf/util/evlist.c | 2 +- > tools/perf/util/evlist.h | 1 + > 4 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt > index 1a766d4a2233..1ffb510606af 100644 > --- a/tools/perf/Documentation/perf-stat.txt > +++ b/tools/perf/Documentation/perf-stat.txt > @@ -382,6 +382,10 @@ 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. > > +--no-affinity:: > +Don't change scheduler affinities when iterating over CPUs. Disables > +an optimization aimed at minimizing interprocessor interrupts. > + > STAT RECORD > ----------- > Stores stat data into perf data file. > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index aec93b91fd11..fa42b08bd1df 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -2415,6 +2415,7 @@ static int parse_tpebs_mode(const struct option *opt, const char *str, > int cmd_stat(int argc, const char **argv) > { > struct opt_aggr_mode opt_mode = {}; > + bool no_affinity = false; > struct option stat_options[] = { > OPT_BOOLEAN('T', "transaction", &transaction_run, > "hardware transaction statistics"), > @@ -2543,6 +2544,8 @@ int cmd_stat(int argc, const char **argv) > "don't print 'summary' for CSV summary output"), > OPT_BOOLEAN(0, "quiet", &quiet, > "don't print any output, messages or warnings (useful with record)"), > + OPT_BOOLEAN(0, "no-affinity", &no_affinity, > + "don't allow affinity optimizations aimed at reducing IPIs"), I know you want to add an option to disable the behaivor, but I think it'd better to have a positive option like just '--affinity'. Then we will have '--no-affinity' for free. :) The current form will allow '--no-no-affinity'. Then the variable also can be 'enable_affinity' or so. You can mention --no-affinity in the help message and the man page document so that users can discover the intention. Thanks, Namhyung > OPT_CALLBACK(0, "cputype", &evsel_list, "hybrid cpu type", > "Only enable events on applying cpu with this type " > "for hybrid platform (e.g. core or atom)", > @@ -2600,6 +2603,9 @@ int cmd_stat(int argc, const char **argv) > } else > stat_config.csv_sep = DEFAULT_SEPARATOR; > > + if (no_affinity) > + evsel_list->no_affinity = true; > + > if (argc && strlen(argv[0]) > 2 && strstarts("record", argv[0])) { > argc = __cmd_record(stat_options, &opt_mode, argc, argv); > if (argc < 0) > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c > index fc3dae7cdfca..53c8e974de8b 100644 > --- a/tools/perf/util/evlist.c > +++ b/tools/perf/util/evlist.c > @@ -368,7 +368,7 @@ static bool evlist__use_affinity(struct evlist *evlist) > struct perf_cpu_map *used_cpus = NULL; > bool ret = false; > > - if (!evlist->core.user_requested_cpus || > + if (evlist->no_affinity || !evlist->core.user_requested_cpus || > cpu_map__is_dummy(evlist->core.user_requested_cpus)) > return false; > > diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h > index b4604c3f03d6..c7ba0e0b2219 100644 > --- a/tools/perf/util/evlist.h > +++ b/tools/perf/util/evlist.h > @@ -59,6 +59,7 @@ struct event_enable_timer; > struct evlist { > struct perf_evlist core; > bool enabled; > + bool no_affinity; > int id_pos; > int is_pos; > int nr_br_cntr; > -- > 2.51.2.1041.gc1ab5b90ca-goog >