From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 379F845C14; Wed, 19 Feb 2025 13:30:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739971830; cv=none; b=sIvgZ9TWcVVfc0N+bH5x5vh4kFLEIzIsRkdpreXu9Qv1eNBCmb+XWw+aDkQZWrJTz3ARJv8L7P6inhC2tMpWS7FEPDvEUWUtQF04tgD8bKFchVNPfWBaDzvLoRgHie53ClStHEe2IBucoZ02eG/n70KAjEZf1lOnebXbDrFOgxQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739971830; c=relaxed/simple; bh=dFMCeJ7t4DLVGLCE/Oqtjh/QIoS5YYqkSRw7tgjyIks=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tMt0aGhOdcD8jbFP+/Zy1wNPEcP7gXOk6h2OMthmMsV3IxdzOE21/IMbuNOYBpjcayqyyQ0pz2AusKvV0tv16dZXx1qLuyiyYrc5QSQxhhGQp1vAP9YtJ+mNCGOxptYedUjCWp/pxMHYPouN1yh6ilpIUi8mSwpGOZCjltWhU4Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A27311682; Wed, 19 Feb 2025 05:30:46 -0800 (PST) Received: from e133380.arm.com (e133380.arm.com [10.1.197.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7931E3F59E; Wed, 19 Feb 2025 05:30:23 -0800 (PST) Date: Wed, 19 Feb 2025 13:30:20 +0000 From: Dave Martin To: Reinette Chatre Cc: "Moger, Babu" , Babu Moger , corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, tony.luck@intel.com, peternewman@google.com, x86@kernel.org, hpa@zytor.com, paulmck@kernel.org, akpm@linux-foundation.org, thuth@redhat.com, rostedt@goodmis.org, xiongwei.song@windriver.com, pawan.kumar.gupta@linux.intel.com, daniel.sneddon@linux.intel.com, jpoimboe@kernel.org, perry.yuan@amd.com, sandipan.das@amd.com, kai.huang@intel.com, xiaoyao.li@intel.com, seanjc@google.com, xin3.li@intel.com, andrew.cooper3@citrix.com, ebiggers@google.com, mario.limonciello@amd.com, james.morse@arm.com, tan.shaopeng@fujitsu.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, maciej.wieczor-retman@intel.com, eranian@google.com Subject: Re: [PATCH v11 11/23] x86/resctrl: Introduce mbm_cntr_cfg to track assignable counters at domain Message-ID: References: <30652061d4a21eb5952a1323b76ca70927412a30.1737577229.git.babu.moger@amd.com> <7375cacc-5800-487c-bd8a-7ea11e694598@amd.com> <2f1d5857-7f32-4bde-9b12-77fb2b4464da@intel.com> Precedence: bulk X-Mailing-List: linux-doc@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: <2f1d5857-7f32-4bde-9b12-77fb2b4464da@intel.com> Hi, On Mon, Feb 10, 2025 at 10:10:26AM -0800, Reinette Chatre wrote: > Hi Babu, > > On 2/7/25 10:23 AM, Moger, Babu wrote: > > On 2/5/2025 5:57 PM, Reinette Chatre wrote: > >> On 1/22/25 12:20 PM, Babu Moger wrote: [...] > >>> MBM events of a monitoring group is tracked by hardware. Such queries > >>> are acceptable because of a very small number of assignable counters. > >> > >> It is not obvious what "very small number" means. Is it possible to give > >> a range to help reader understand the motivation? > > > > How about? > > > > MBM events of a monitoring group is tracked by hardware. Such queries > > are acceptable because of a very small number of assignable counters(32 to 64). > > Yes, thank you. This helps to understand the claim. > > Reinette Do these queries only happen when userspace reads an mbm_assign_control file? It might be worth documenting somewhere that writing and (especially) reading an mbm_assign_control file is not intended to be super-fast. It feels like userspace should not generally rely on reading mbm_assign_control files except for diagnostic purposes, or occasional read-modify-write transformations. Or do expect some other usage model that makes this a hotter path? Cheers ---Dave