From nobody Sun Feb 8 23:35:06 2026 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E3C512EE5FE for ; Thu, 6 Nov 2025 07:13:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762413184; cv=none; b=ZSkRzbkg6MPmsyvIPyz1s9ktMzJ/IrH0GgWRL1YlIcGndvy2W0ki+NW0We41fq/7a2Lt3PaIRFZDeJCl4r63qBSgo+Gbcp1FM+pMmNOW8SxVjfu6l9lNtrWFfnE2QTu6aj2l9u9W6thc2r7tbjCZQH3ddNSFLX1NGSWe+iBuKDo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762413184; c=relaxed/simple; bh=baW/PP9vuOXOepoc3ZzKNVeVqn+YVFSWu3Wdb3YH+qI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Content-Type; b=efTF55ycswGTox0sdvigmbvuGTW3GsQJynKFvsTYgf+lFPdG7jkp5KIDHI/f6S0rDSr+DO+fEqZ8g2RiTJ15IdYtHP8aZu3egJTt23Qvxkwg5/rHHXiOQh6TQtlaW4BGjKa+C/Qm/IYQLt28W6m715KbPjNeCQkDm3RmbgDaaw4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--irogers.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=jp41COIl; arc=none smtp.client-ip=209.85.215.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--irogers.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="jp41COIl" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-b9ceccbd7e8so118656a12.0 for ; Wed, 05 Nov 2025 23:13:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1762413182; x=1763017982; darn=vger.kernel.org; h=to:from:subject:message-id:references:mime-version:in-reply-to:date :from:to:cc:subject:date:message-id:reply-to; bh=w9ZhWJR/a4jUzE3S599HAQn9Ex0tBJc68Cyk87AziX0=; b=jp41COIl3kshd8F54ki0AIAlhzfrPWu+a82JLFbTtanQYzf3w2GwDWbmgw58zdtO+c lVp2ALCQv0qEPuydZ9UU9wr6eO2sbiB8SUzfhs9ZDpDr8eYBpyQcwCxDqqQrsJ9rJI6x S8sRlawflEhk0hBXpGNsYUUGLq098Mz8WTYdojD6bLzLphz3DPFaiE/7qOm10AtWIPEj 08SKLuEQDJBuj/CyGHLSwzHMISqb8KaqTvj9Xvde88d3Jnt+aXRKTDoShNY3+lsZqzTw L4uuAiAVItluCXHzSC/o3XzWNWLzOG0w3nnZOrv/9gtsvR30CdgW8fDXMO8//f9VSHyU yHZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1762413182; x=1763017982; h=to:from:subject:message-id:references:mime-version:in-reply-to:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=w9ZhWJR/a4jUzE3S599HAQn9Ex0tBJc68Cyk87AziX0=; b=V/OClUPMqnlmsXSrBvLGkCvbWvgXgOlemtqqTqD9cBCiUibfAKNOorctr6WRBb4zzy Rv+SsrK470WqlpujLHLpnU+iH2WlksnLsBybBSRcOW5FmZS3o248JWQGjMlpwkV4y9gA e8lBq8NdRC90Kbq566SObyCeyF723lr70lYeu3qUu72rFmrOBPK8LwLNMBkGDx8/mlbi +BSW3Z+7Hsbl9+IkxcW00TY8lmGpUYqwJr+5G+0UzSZZpyB6M1jD8wuhzoIg4QhKjHYh W4V2fndkIk8D8eGCYC7Kc9MZKW16ODQdw/QoDaujvkwDrrYCXGsao3AODCclk3z3Upt1 YIQQ== X-Forwarded-Encrypted: i=1; AJvYcCXilgLAeKycRjBuap0xYngx56uKcmAPY6Dq3BakpCRTo/T+l+6PT7vFMtHB8LRqywjHyghl6HdQsNDzBfg=@vger.kernel.org X-Gm-Message-State: AOJu0YymR5Rk8+z8tk/oc9CXIdPGPClxrmisPbOtycv6dTVBwdtmHwqc HrtVObK0zbafRU4yLVcNmUgkW+fSDJHYAEkNAx6tPbpTUpBZp8RH+S58GoMb6wqMuYcur0cFCrY J/Tk1W6A7hA== X-Google-Smtp-Source: AGHT+IE226Se0eAuwakSfAwq7yVrK/hma19wGPnIC5iTTdwVG+sTf6vfeyZ6rqw5EP3YtKPbdGB+kq+zuvoc X-Received: from dlbrs16.prod.google.com ([2002:a05:7022:f690:b0:119:49ca:6b95]) (user=irogers job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:12c3:b0:341:6d44:dfd5 with SMTP id adf61e73a8af0-34f8580ad59mr8097329637.33.1762413182363; Wed, 05 Nov 2025 23:13:02 -0800 (PST) Date: Wed, 5 Nov 2025 23:12:40 -0800 In-Reply-To: <20251106071241.141234-1-irogers@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251106071241.141234-1-irogers@google.com> X-Mailer: git-send-email 2.51.2.1041.gc1ab5b90ca-goog Message-ID: <20251106071241.141234-10-irogers@google.com> Subject: [PATCH v3 9/9] perf stat: Add no-affinity flag From: Ian Rogers To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Alexander Shishkin , Jiri Olsa , Ian Rogers , 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 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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/Documentat= ion/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. =20 +--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 75ff08c5f0ed..f2f149f0c2cf 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -2479,6 +2479,7 @@ 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 =3D {}; + bool no_affinity =3D false; struct option stat_options[] =3D { OPT_BOOLEAN('T', "transaction", &transaction_run, "hardware transaction statistics"), @@ -2607,6 +2608,8 @@ 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"), 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)", @@ -2664,6 +2667,9 @@ int cmd_stat(int argc, const char **argv) } else stat_config.csv_sep =3D DEFAULT_SEPARATOR; =20 + if (no_affinity) + evsel_list->no_affinity =3D true; + if (argc && strlen(argv[0]) > 2 && strstarts("record", argv[0])) { argc =3D __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 =3D NULL; bool ret =3D false; =20 - 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; =20 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; --=20 2.51.2.1041.gc1ab5b90ca-goog