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 A0716F8D761 for ; Thu, 16 Apr 2026 17:03:19 +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=P+WTaxx++A4fmUPLH8/ep/XSvkYJBE9H9Qw/DE/nnB4=; b=qAMkh0vB719uosHqZKSYDPEyHB 3rx6VFGwYdpebYrziOaGQRD/G02d18G8TUoqQ5Y0g7Lt6+ErGlCkqEWxc6Qy8/irkHva8uy+vLO2d UOG27vifeWILbsgZx2RQqwU6LztN5dOy3SfS9nvD/eM1vn/geUdCo6FWLguafRvQKjEnSBijnN3G6 CnPfF7vpm+uGYciEfbLeGPd0tNGDpNysPWwwbskXj17UyV7BUIT5bcNTW9jEVIfJOuPe5Pq1ZsgqV zJKK0dyrW9jd/F7440GHeI5DpuKS8/T6vFBFWTazkTNNwdhLUUpPbpUBvzyUGfpmMVOUnf1iKlWgt Z1UuXp1w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDQ7V-00000002hE7-0mlt; Thu, 16 Apr 2026 17:03:13 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDQ7T-00000002hDl-0ecP for linux-arm-kernel@lists.infradead.org; Thu, 16 Apr 2026 17:03:12 +0000 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 EB91B24E9; Thu, 16 Apr 2026 10:03:02 -0700 (PDT) Received: from [10.1.196.85] (e121345-lin.cambridge.arm.com [10.1.196.85]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D90EB3F7B4; Thu, 16 Apr 2026 10:03:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1776358988; bh=CkT2Mkvuq4h7knuFYjVS0j+7pcNunecYN1l472zFcBU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ioDzWc+syAC3h6+Pv/+21Qijh7CWWtaL3WjagXKgMGHCPNhFYIBCfP2/1QvFa8/8m B8wice+IBUrMmdb+VgUuF1kE9Q5j0Gm44XkEYbnY0QUk7x4WlC3rcl0ewRiBuPsTn9 TDEl21dtvFsHULTY/kZYlL/XWLa3zbJkWbquMKIQ= Message-ID: Date: Thu, 16 Apr 2026 18:03:02 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] raid6: arm64: add SVE optimized implementation for syndrome generation To: Mark Brown Cc: Demian Shulhan , Ard Biesheuvel , Christoph Hellwig , Mark Rutland , Song Liu , Yu Kuai , Will Deacon , Catalin Marinas , linux-arm-kernel@lists.infradead.org, Li Nan , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org References: <9a12e043-8200-4650-bfe2-cbece57a4f87@app.fastmail.com> <20260331063659.GA2061@lst.de> <5158e4e0-3275-4c29-a8fc-2dfabc13a69d@app.fastmail.com> <8db4defe-8b5e-4cc3-880b-72d46510b034@arm.com> From: Robin Murphy Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260416_100311_244265_A99EE561 X-CRM114-Status: GOOD ( 12.23 ) 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 On 16/04/2026 5:47 pm, Mark Brown wrote: > On Thu, Apr 16, 2026 at 05:26:08PM +0100, Robin Murphy wrote: > >> Unless you've got a CPU with truly big wide vector units that _can't_ be >> fully utilised by ASMID ops, then SVE is only really offering whatever >> incidental benefits fall out of smaller code size. However, if you do have >> those wider vectors, then the cost of correctly saving/restoring the SVE >> state - of which a userspace benchmark isn't likely to be very >> representative - is also going to scale up significantly. > > The other case will be when there's some SVE only extension that > accelerates something that's relevant for the algorithm. That's not > really a thing at present but I imagine that we'll run into that at some > point. Indeed - I was implicitly thinking in terms of things that _are_ just transliterated from NEON to SVE, where the primary gain is stuff like predicate loops, but even that _could_ potentially be enough to justify an argument in-kernel SVE (using a 128-bit VL to keep the additional state/cost to a minimum). Cheers, Robin.