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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 103D3C55822 for ; Tue, 4 Aug 2026 22:06:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=xFvycaE6HyRvj662ncTXzZ2lEUnpPku3d1eDVKU1XJU=; b=Z+YLHd5iCzE5d/sdwJvSzRXBY2 90mYPZ6XN7L/jNc+HMP5zuJZ6XQ3RCgkAR4r7vK40fGRCIicHwMiS+7O9965tyKNw1km3/f1HkRwL lLk1pGIc+Y3IJjQvyFDol5lJN3H8K3G/1oa/8DllT3k+ChSnLILgfsF36lWlKY/2gQXrtZhw1h5KK 3Ig9jhmRLS2BHviz0HsJwjuoT3iFaPGDWGATa3KoAn+8N523d83JKpuohXNEYPBtWhwdmnEQ/kbFq U/m8Cjd6it50BmgFSJ9336PWEmGn+WHQQkazo47D3U0lqdeO0rXhYU1hvvQGSAhyVlCx9ReNWWmIg OeC4jBsw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrNGo-00000002r1p-3INL; Tue, 04 Aug 2026 22:05:58 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrNGm-00000002r1h-1LJl for linux-arm-kernel@lists.infradead.org; Tue, 04 Aug 2026 22:05:56 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0531141760; Tue, 4 Aug 2026 22:05:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5FD101F000E9; Tue, 4 Aug 2026 22:05:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785881154; bh=xFvycaE6HyRvj662ncTXzZ2lEUnpPku3d1eDVKU1XJU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=S0fkrlLdOdV6vmDx7sATY5Wbc3Ki/D2mR7nyYdpaLQIg9+EIP6+0yZey5MClouwfw 2r4FUQxf/+7EymJKF08yQq0sOy4Ba+t9CUwoZOkWxiW+dlF7PqZJMJ0rM6KRFz3Lbn 0Y5+Otc/BsOW5Xh2EvfEdDCxUzKDcHoyAJ3S6wfdggFf0/oZiAMdG/5X8iUyXr2lZc 6Uh8WwNNc5AnKVVlWjg3sF3PQ5c9l5xdIAtcRJeEaqIYe4x5RNFCRcupDJuRpPs6wf 31bnIwJCiTNv/nmCaige1dL14rs4IzpcKfCnOBkvsYeZMpOPZPhgHmA1PE8LzUbYzt YTnIfrCSYbcsQ== Message-ID: <94c7988a-3ecf-4b26-b0a8-011bdc76283b@kernel.org> Date: Wed, 5 Aug 2026 00:05:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC v2 PATCH 0/16] Optimize this_cpu_*() ops for non-x86 (ARM64 for this series) To: Yang Shi , "Lorenzo Stoakes (ARM)" , Linus Torvalds Cc: "Christoph Lameter (Ampere)" , Mark Rutland , Ryan Roberts , dennis@kernel.org, tj@kernel.org, urezki@gmail.com, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Jason Gunthorpe References: <20260715180455.515692-1-yang@os.amperecomputing.com> <0344c559-1959-4531-9265-d5a5180eb7cd@arm.com> <25d1e09b-53e4-7cd5-87db-b58437e4e690@gentwo.org> <4887267b-dc26-4c33-96ca-8dff054a0d1f@kernel.org> <69f4cd9c-bd6c-4e5d-b8d1-a7be8408a57a@os.amperecomputing.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org >> The LSF session was not encouraging ([2]) and as an mm maintainer I'm not at all >> happy with this myself, nor does the arm64 community seem all that enthused so I >> would against gently suggest to Christoph to be a little more open-minded about >> the the proposed alternative which he seems to have dismissed out of hand. > > Nobody disagreed Mark's approach also achieved good result, we just thought the > series can do better. Okay, you thought it can do better. Did you only think that or did you measure it? The cover letter obviously only compares to upstream Linux, not to Mark's series. Are there performance results I am missing that directly show that the additional instructions have an actual measurable performance impact? That's really all we are asking for. If there is a measurable performance difference, great. Share the results or point us at them if we missed them. -- Cheers, David