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[23.128.96.18]) by mx.google.com with ESMTP id a4si15258924ejj.485.2021.06.15.09.49.44; Tue, 15 Jun 2021 09:50:07 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229976AbhFOQu4 (ORCPT + 99 others); Tue, 15 Jun 2021 12:50:56 -0400 Received: from foss.arm.com ([217.140.110.172]:40768 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229931AbhFOQuz (ORCPT ); Tue, 15 Jun 2021 12:50:55 -0400 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 4C12213A1; Tue, 15 Jun 2021 09:48:50 -0700 (PDT) Received: from [192.168.0.14] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 44E133F694; Tue, 15 Jun 2021 09:48:48 -0700 (PDT) Subject: Re: [PATCH v4 00/24] x86/resctrl: Merge the CDP resources To: Reinette Chatre , x86@kernel.org, linux-kernel@vger.kernel.org Cc: Fenghua Yu , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Babu Moger , shameerali.kolothum.thodi@huawei.com, Jamie Iles , D Scott Phillips OS , lcherian@marvell.com, "Luck, Tony" References: <20210614200941.12383-1-james.morse@arm.com> From: James Morse Message-ID: <4d2ba7c1-395b-d1ec-c92b-f906e2a551a1@arm.com> Date: Tue, 15 Jun 2021 17:48:25 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Reinette, On 15/06/2021 17:16, Reinette Chatre wrote: > On 6/14/2021 1:09 PM, James Morse wrote: >> This series re-folds the resctrl code so the CDP resources (L3CODE et al) >> behaviour is all contained in the filesystem parts, with a minimum amount >> of arch specific code. [..] >> This series collapses the CODE/DATA resources, moving all the user-visible >> resctrl ABI into what becomes the filesystem code. CDP becomes the type of >> configuration being applied to a cache. This is done by adding a >> struct resctrl_schema to the parts of resctrl that will move to fs. This >> holds the arch-code resource that is in use for this schema, along with >> other properties like the name, and whether the configuration being applied >> is CODE/DATA/BOTH. >> >> This lets us fold the extra resources out of the arch code so that they >> don't need to be duplicated if the equivalent feature to CDP is missing, or >> implemented in a different way. [...] >> This series is based on v5.12-rc6, and can be retrieved from: >> git://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git mpam/resctrl_merge_cdp/v4 > For the most part I think this series looks good. The one thing I am concerned about is > the resctrl user interface change. On a system that supports L3 CDP there is a visible > change when CDP is not enabled: > > Before this series: > # cat schemata >    L3:0=fffff;1=fffff > > After this series: > # cat schemata > L3:0=fffff;1=fffff Hmm, I thought I'd fixed this with v2, ... I see this is subtly different. This could be tweaked by getting schemata_list_add() to include the length of the longest suffix if the resource supports CDP, but its not enabled. (Discovering that means cdp_capable moves to be something the 'fs' bits of resctrl can see.) I'm a little nervous 'adding 4 spaces' because user-space expects them. (I agree if it breaks user-space it has to be done). I guess this is the problem with string parsing as part of the interface! I assume that in the (distant) future having CDP capable resources with names more than 2 characters isn't going to be a problem. (I don't have an example) > There are a few user space tools that parse the resctrl schemata file and it may be easier > to keep the interface consistent than to find and audit them all to ensure they will keep > working. > Apart from that, I do think that the dmesg change that Babu pointed out deserves a mention > in the cover letter. I agree with your response in this regard but this is indeed a user > visible change and if anybody has issue with that then mentioning it in the cover letter > will hopefully catch it sooner. Ah, okay. > A heads-up is that there are some kernel-doc fixups in the works that will conflict with > your series. You yourself fix at least one of these kernel-doc issues in this series - the > description of mbm_width in the first patch. I will ask the submitter of the kernel-doc > fixups to use your text to help with the merging. Please point me at something to rebase onto! (as far as I can see, tip/x86/cache hasn't moved) > Finally, I did catch a few typos that I will respond to individually. Thanks! James