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 0A16DFF493A for ; Mon, 30 Mar 2026 05:30:20 +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:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=QFBQfsZr5GhDBdJSNw2P+ylTzm0pNue9CjzoFJeGiD0=; b=eDGs4ny5ZhCepwYag4Ur5uleE9 r9U4fj3ThjKWg7JX5jLbESK7oY2pJ0ayJ3NmqumhAFxIibRrSDAmNMmXpfC0pXkQvyCbsp9b2VofE lz672LdzRTA1jD6w2hmCk+RnTV8vUgVQz3MgPH3zFHuYiGMGOa4FN1WHHg4mcJSApx7cUHymcqnhE ZRnKkPkaEXYrE1Xfnr6NnNQP3E5ENUkREoj5FdVVG298rbYYPbTmt3Q5ImY/90yVCx6Yi1dug5Mlh CwfE2rSDVRfpBnlOSS7JflRo3ia1fzA61w/X7mEfoiCES9nnz9K2pbvy+6FOimHKpHqwkFjYPlJZf 9QfwMwsw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w75CX-0000000Adit-2Bgm; Mon, 30 Mar 2026 05:30:13 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w75CU-0000000Adhs-14GD for linux-arm-kernel@lists.infradead.org; Mon, 30 Mar 2026 05:30:11 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 2EBDF68B05; Mon, 30 Mar 2026 07:30:04 +0200 (CEST) Date: Mon, 30 Mar 2026 07:30:03 +0200 From: Christoph Hellwig To: Demian Shulhan Cc: Mark Rutland , Ard Biesheuvel , Christoph Hellwig , Song Liu , Yu Kuai , Will Deacon , Catalin Marinas , broonie@kernel.org, linux-arm-kernel@lists.infradead.org, robin.murphy@arm.com, Li Nan , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] raid6: arm64: add SVE optimized implementation for syndrome generation Message-ID: <20260330053003.GA4736@lst.de> References: <20260318150245.3080719-1-demyansh@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260329_223010_460295_362BA41F X-CRM114-Status: GOOD ( 16.42 ) 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 Sun, Mar 29, 2026 at 04:01:06PM +0300, Demian Shulhan wrote: > Furthermore, as Christoph suggested, I tested scalability on wider > arrays since the default kernel benchmark is hardcoded to 8 disks, > which doesn't give the unrolled SVE loop enough data to shine. On a > 16-disk array, svex4 hits 15.1 GB/s compared to 8.0 GB/s for neonx4. > On a 24-disk array, while neonx4 chokes and drops to 7.8 GB/s, svex4 > maintains a stable 15.0 GB/s — effectively doubling the throughput.I > agree this patch should be put on hold for now. My intention is to > leave these numbers here as evidence that implementing SVE context > preservation in the kernel (the "good use case") is highly justifiable > from both a power-efficiency and a wide-array throughput perspective > for modern ARM64 hardware. > > Thanks again for your time and time and review! To me this sounds like an interesting case for a SVE kernel API. But I'm not relly knowledgeable enough to provide one to help with testing this further.