From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20124C433EF for ; Tue, 3 May 2022 23:54:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 78E5A6B0071; Tue, 3 May 2022 19:54:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7173F6B0073; Tue, 3 May 2022 19:54:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 58FDE6B0074; Tue, 3 May 2022 19:54:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 429E16B0071 for ; Tue, 3 May 2022 19:54:18 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id 11F236099E for ; Tue, 3 May 2022 23:54:18 +0000 (UTC) X-FDA: 79426088196.07.5DA46C9 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by imf11.hostedemail.com (Postfix) with ESMTP id 5C4264007C for ; Tue, 3 May 2022 23:54:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1651622057; x=1683158057; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=K8SvhxQm1P62rJiCvMA6jYehYxpt5BXqhVT4BJHzqCc=; b=K8DqS281zN8PZqZkOftfCSRECewDA/D/esYdIMLSbxkdPTQCbC2dmmv4 3wWkZpO+supsNISe74sW5gHl/hO+3vXaFmE+R0akYc3N53p64TQoKr09T 43ldAI2zvJVGutstxP71dTVvDk9SYZf3Ateb64FUkO2UoE5EyI51Xky1U 5S24B12NCNgsTsGJAkPiqXN5N/S+lSGU93/warr0ag9I1J9YFcHtx3D3f KMEEOuWqXwufcV/QTs429FJiH0+MHcX/aZ0hoAis2ymWkzLOlfCLMTGrW RfV+YCCBab30ahXQq/cjn5TN/96GY3BBMdI+3rkhWqOjEEw0lEJkQ5w9w g==; X-IronPort-AV: E=McAfee;i="6400,9594,10336"; a="265209913" X-IronPort-AV: E=Sophos;i="5.91,196,1647327600"; d="scan'208";a="265209913" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 May 2022 16:54:15 -0700 X-IronPort-AV: E=Sophos;i="5.91,196,1647327600"; d="scan'208";a="664202274" Received: from dbandax-mobl2.amr.corp.intel.com (HELO [10.209.188.251]) ([10.209.188.251]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 May 2022 16:54:14 -0700 Message-ID: <9fb22767-54de-d316-7e6b-5aac375c9c49@intel.com> Date: Tue, 3 May 2022 16:54:34 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: RFC: Memory Tiering Kernel Interfaces Content-Language: en-US To: Alistair Popple Cc: Davidlohr Bueso , Wei Xu , Andrew Morton , Dave Hansen , Huang Ying , Dan Williams , Yang Shi , Linux MM , Greg Thelen , "Aneesh Kumar K.V" , Jagdish Gediya , Linux Kernel Mailing List , Michal Hocko , Baolin Wang , Brice Goglin , Feng Tang , Jonathan.Cameron@huawei.com References: <20220501175813.tvytoosygtqlh3nn@offworld> <87o80eh65f.fsf@nvdebian.thelocal> <87mtfygoxs.fsf@nvdebian.thelocal> From: Dave Hansen In-Reply-To: <87mtfygoxs.fsf@nvdebian.thelocal> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=K8DqS281; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf11.hostedemail.com: domain of dave.hansen@intel.com has no SPF policy when checking 192.55.52.93) smtp.mailfrom=dave.hansen@intel.com X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5C4264007C X-Rspam-User: X-Stat-Signature: jcyxqcwdp191jrbu9irpnjmpguex7cja X-HE-Tag: 1651622053-94229 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 5/3/22 15:35, Alistair Popple wrote: > Not entirely true. The GPUs on POWER9 have performance counters capable of > collecting this kind of information for memory accessed from the GPU. I will > admit though that sadly most people probably don't have a P9 sitting under their > desk :) Well, x86 CPUs have performance monitoring hardware that can theoretically collect physical access information too. But, this performance monitoring hardware wasn't designed for this specific use case in mind. So, in practice, these events (PEBS) weren't very useful for driving memory tiering. Are you saying that the GPUs on POWER9 have performance counters that can drive memory tiering in practice? I'd be curious if there's working code to show how they get used. Maybe the hardware is better than the x86 PMU or the software consuming it is more clever than what we did. But, I'd love to see it either way.