From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.10]) (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 D22C51F7575; Tue, 18 Nov 2025 23:19:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763507951; cv=none; b=EBrWxc1hPWP5XiqNleImBt0/0S96mWLMU/PURgh++QBSvloSg2qgU5JAQo0+QwmUbKiJLnH4t/cLjFwzeop6QqjqxPBzH4bhb+hlKhI4AJj9SLg/kD09GVEFRrCebVokLPezW7XezB6bbPMZ+qdC1/Pe4EjimFjhL9q+kLkuge8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763507951; c=relaxed/simple; bh=Tx2ttj0SiijrBecv7SJgYHcj16qh0ZjLnawjZ00nlkw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=H8dRL3B7S3u5J9pBSwf3LwDzYNX97pRuDuW/QZSp2YkzBCXJzh8nstSq4JgFZlc2EdUjyCNbaK+Z3AgyjItu62lRj44sGIRWPTDH7xpyZPPneOicI492YJGEJ6FoNitf8UYn7OF0c/xnhnYAzFwpUtS4IK92I/VnrOfmzN1C/1c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=R6W9irJj; arc=none smtp.client-ip=192.198.163.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="R6W9irJj" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1763507950; x=1795043950; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=Tx2ttj0SiijrBecv7SJgYHcj16qh0ZjLnawjZ00nlkw=; b=R6W9irJj6SrzB7JRLqC4wXMmry833TnnXht394YeZKuSLUd9S+OERz7m U6DC3/z4pb6glFXegFwE4O3grk0Z78LAHrQdS5rHcSpeV7LohjARpkJao Uvl3FzEbVUnRUibLyqw4V+++b4QLbfi+R7KGH2bcZOlQPPiPqmhFbjhW6 puyReq71yE6RZmalfyA/UeSoupmCmmbCEIGqx50Jz5Zux0VLCzzQd2HrG l9uHEQftxq6y4Q3AV37xlIASS0pTTdm9bbvWrTTDydY0mKXilNg8ur1DQ 5zrmT98OGmSsudoE1nYFVr98+O77W5eQqamJyYL5PWHNB5Yp/0PAPkIaU g==; X-CSE-ConnectionGUID: c+4fqpfnSmKyl/eCgVhFwg== X-CSE-MsgGUID: vUE+E6BJRMiPaTRXYiJWRg== X-IronPort-AV: E=McAfee;i="6800,10657,11617"; a="76896111" X-IronPort-AV: E=Sophos;i="6.19,314,1754982000"; d="scan'208";a="76896111" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Nov 2025 15:19:08 -0800 X-CSE-ConnectionGUID: 7T45Qrm6TpePfTxpLFZEiQ== X-CSE-MsgGUID: wrb1CVCUQhaDcNaHNemiSg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,314,1754982000"; d="scan'208";a="190686139" Received: from tassilo.jf.intel.com (HELO tassilo) ([10.54.38.190]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Nov 2025 15:19:08 -0800 Date: Tue, 18 Nov 2025 15:19:06 -0800 From: Andi Kleen To: Ian Rogers Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , 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, Dapeng Mi Subject: Re: [PATCH v5 3/3] perf stat: Add no-affinity flag Message-ID: References: <20251118211326.1840989-1-irogers@google.com> <20251118211326.1840989-4-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=us-ascii Content-Disposition: inline In-Reply-To: <20251118211326.1840989-4-irogers@google.com> On Tue, Nov 18, 2025 at 01:13:26PM -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. Like i wrote earlier a much better fix for starvation is to use real-time priority instead of the old IPI storms this flag is bringing back. -Andi