From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.7]) (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 8D1B318EFD4; Thu, 22 May 2025 17:21:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747934469; cv=none; b=Or9EjEtBlTM1SJOQMphGau3lJ8DMRktPkwMSkdayiL/JrKOysU4SLf5ZEzCEbB/ux2U/qfeSFyry4AA6xRtlPFnf2+4xrCGNPNX7rwoLdmfgUdFaHAFykiMCVsWjyDXB9BXaiFlx8/F9Tt3rpE+4Jz49OmnPX1A/aMg+aWZoGN0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747934469; c=relaxed/simple; bh=meBhFZpR93iGhBpH25sRiAYWI/AL3rJJZhbmq7MKvFo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=X1BmjSDSTwEgu6Veu5NIcT/sQaIqmL8skqHGvnmJCNwBqg7HPn0ZF+95RK82VHsgubXG+MSLXyq4nScuuffxHOUdqenNEptdgtHCJlrIlGJbpuxWFpP2wVFd3QxMhdSVrVwRlF0Lij2K14WPdHaMgKJdCg0GjxnhFm+wxL3j2oA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=B1BBj2FY; arc=none smtp.client-ip=192.198.163.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="B1BBj2FY" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1747934468; x=1779470468; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=meBhFZpR93iGhBpH25sRiAYWI/AL3rJJZhbmq7MKvFo=; b=B1BBj2FYlIjaS5GIjWKjcg7olYvglRccdnq7hJOmWepR843Kpy4JxqNu CttlBuq03GKrSKMce26Vv5LE2KbYQopnF83ZqlBXVRRoGTGDSxSGfiZMI HImeTPofjQZcdbNNkuTltO08ib80DmBuAd9W+rJ+0umB0Ex0klRcef716 5XP9+efAd/Cy7aoBzLU0jXQK+hkmKjLUY/UtuGpNWr1FEiE3QTELMPV8s 5GabDiQI1wMXbN3aDU/JsC7xw1wxbvJdjqG7NVj30XeiCWeQJUEWN3unW tPb0X81DknPwL00YOl6PsFdkTIZFSw9e2fYCXXG+s3tcONhzZYv9rXBPt w==; X-CSE-ConnectionGUID: vze3mEi5S52UfzrrGky6IA== X-CSE-MsgGUID: 1HRR6CK3QuSvbHRQZ9Li8w== X-IronPort-AV: E=McAfee;i="6700,10204,11441"; a="75372025" X-IronPort-AV: E=Sophos;i="6.15,306,1739865600"; d="scan'208";a="75372025" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 May 2025 10:21:06 -0700 X-CSE-ConnectionGUID: NSuJojDyQNq5mgYkId4n5g== X-CSE-MsgGUID: 5JD9Ntu7QxKrD9ag2JWnjA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.15,306,1739865600"; d="scan'208";a="145852227" Received: from agluck-desk3.sc.intel.com (HELO agluck-desk3) ([172.25.103.51]) by orviesa005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 May 2025 10:21:05 -0700 Date: Thu, 22 May 2025 10:21:03 -0700 From: "Luck, Tony" To: Peter Newman Cc: "Chatre, Reinette" , "Moger, Babu" , "babu.moger@amd.com" , "corbet@lwn.net" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "james.morse@arm.com" , "dave.martin@arm.com" , "fenghuay@nvidia.com" , "x86@kernel.org" , "hpa@zytor.com" , "paulmck@kernel.org" , "akpm@linux-foundation.org" , "thuth@redhat.com" , "rostedt@goodmis.org" , "ardb@kernel.org" , "gregkh@linuxfoundation.org" , "daniel.sneddon@linux.intel.com" , "jpoimboe@kernel.org" , "alexandre.chartre@oracle.com" , "pawan.kumar.gupta@linux.intel.com" , "thomas.lendacky@amd.com" , "perry.yuan@amd.com" , "seanjc@google.com" , "Huang, Kai" , "Li, Xiaoyao" , "kan.liang@linux.intel.com" , "Li, Xin3" , "ebiggers@google.com" , "xin@zytor.com" , "Mehta, Sohil" , "andrew.cooper3@citrix.com" , "mario.limonciello@amd.com" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Wieczor-Retman, Maciej" , "Eranian, Stephane" , "Xiaojian.Du@amd.com" , "gautham.shenoy@amd.com" Subject: Re: [PATCH v13 00/27] x86/resctrl : Support AMD Assignable Bandwidth Monitoring Counters (ABMC) Message-ID: References: <6c77b065-a54e-4b9c-a4cf-8b81676f2ab2@amd.com> <92bcab75-72c6-46d4-97a2-119e7124c90c@amd.com> <11465976-f030-4c1b-88c6-3eebf0c8f13b@intel.com> <7f10fa69-d1fe-4748-b10c-fa0c9b60bd66@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@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: > > Maybe assign one of the limited supply of RMIDs for these "unmonitored" > > tasks. Populate a resctrl group named "unmonitored" that lists all the > > unmonitored tasks in a (read-only) "tasks" file. And supply all the counts > > for these tasks in normal looking "mon_data" directory. > > I needed to switch to an rdtgroup struct pointer rather than hardware > IDs in the task structure to indicate group membership[1], otherwise > it's not possible to determine which tasks are in a group when it > doesn't have a unique HW ID value. > > Also this is required for shared assignment so that changing a group's > IDs in a domain only requires updating running tasks rather than > needing to search the entire task list, which would lead to the same > problem we encountered in mongroup rename[2]. Having a pointer to the rdtgroup in the task structure does make file system operations easier. But the cost appears to be more complexity (and memory references) in the context switch code. Your patch[1] seems to do some extra work outside of the static_branch protected sections. So has a cost to context switch even if resctrl is not in use. Chasing pointers "closid = rgrp->mon.parent->closid;" could be expensive when those miss in the cache. > > -Peter > > [1] https://lore.kernel.org/lkml/20240325172707.73966-5-peternewman@google.com/ > [2] https://lore.kernel.org/lkml/CALPaoCh0SbG1+VbbgcxjubE7Cc2Pb6QqhG3NH6X=WwsNfqNjtA@mail.gmail.com/ -Tony