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 BC30ECD4F26 for ; Fri, 26 Jun 2026 05:47:37 +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-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ZusCNbIc8LrRJZFkRoqPByl27UFG7XUmGsTF9h8YKP0=; b=dOLV9HBfGVy2HP2ziv4IWWhM2H GPr+fty5J4vf2TLEmSw20uDLP7iQ7f66BEI0O4qpEIcSa7nmkZdYtgkTe2J7acc7nXrmDRPkbNpb6 K379q72ismOpVTJtBTbFJOSJer+zBR44v/bIbuCizr3bVEnHVahPpN+jENaCL0CaFjgUijw9aJsjl enD4xVPwOOOA+0KqbOR/sm8upPmVmHbO6xJ3GtarX8gtPwp1jhVxXctTziIWKIhZ3ekmEFkGTtpGe HGztRG4qXfCxyUpFA+9KOyS3DrROvVKYce6xkOsGb4kosHExPGzfjEJR2HzKkUD4AIkEfO/aANsAV 1CoeoL5g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wczPd-0000000AXcT-0jYt; Fri, 26 Jun 2026 05:47:37 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wczPb-0000000AXbX-1eT7 for linux-um@lists.infradead.org; Fri, 26 Jun 2026 05:47:36 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id DD31968B05; Fri, 26 Jun 2026 07:47:31 +0200 (CEST) Date: Fri, 26 Jun 2026 07:47:31 +0200 From: Christoph Hellwig To: Eric Biggers Cc: x86@kernel.org, linux-um@lists.infradead.org, linux-raid@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , Andrew Morton , David Laight Subject: Re: [PATCH 8/8] lib/raid/xor: x86: Add AVX-512 optimized xor_gen() Message-ID: <20260626054731.GC9629@lst.de> References: <20260626043731.319287-1-ebiggers@kernel.org> <20260626043731.319287-9-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260626043731.319287-9-ebiggers@kernel.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260625_224735_597349_F7EF7BE3 X-CRM114-Status: GOOD ( 11.65 ) X-BeenThere: linux-um@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-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org On Thu, Jun 25, 2026 at 09:37:31PM -0700, Eric Biggers wrote: > + if (IS_ENABLED(CONFIG_X86_64) && boot_cpu_has(X86_FEATURE_AVX512F) && > + !boot_cpu_has(X86_FEATURE_PREFER_YMM)) { > + /* AVX-512 will be the best; no need to try others. */ > + /* !PREFER_YMM excludes CPUs with overly-eager downclocking. */ Can you turn this into a single block comment using full sentences? Right now the two separate comments almost feel contradictory even if I get what you mean. While you're at it also through in a blurb why we dont bother with AVX-512 (number of register, no one in the right mind would bother running high performance code on modern cpus in 32-bit mode).