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 9B80BCCFA0D for ; Wed, 5 Nov 2025 13:25:38 +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=zLLjmh7Zi80OTRhBmaeIPk4X4MfnEcR9oOda/GKVfy0=; b=zfCuBrGl9Yy1AWkFzCsFUjRlMJ G2fqpJakGq+0X871EO0ISJSAfbp4jQLbl8B4+AZdYlC5fhLLZEENU8BjZTkk6xjK4u1V0kwJnMTdH sywuPFOetqbj2zmL5DcCukad2YKH++fp88RUbJ1hy6KCOTDFlMnCTTdtv3fphq3U9rG6qraI+Lby7 7tovuJDY7Q+nGEvbTqsqVvtSg+4rN+KizbK+1R760ASxnvjGsf4m27ZWjoRCYWY230C8YkDEd+tb/ oQh3LqMZ9AkY3u6PYWPFeLEx3iXZ7i1l0cJJWnWvxDrttxR5CBPkNB6ZRqlTNYQ3GtBG4owofN2mH U07bvKvA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vGdW0-0000000DlNB-2i0d; Wed, 05 Nov 2025 13:25:32 +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 1vGdVy-0000000DlMj-0t9V for linux-arm-kernel@lists.infradead.org; Wed, 05 Nov 2025 13:25:32 +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 A8A40169E; Wed, 5 Nov 2025 05:25:20 -0800 (PST) Received: from arm.com (unknown [10.1.26.217]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8CFFF3F63F; Wed, 5 Nov 2025 05:25:27 -0800 (PST) Date: Wed, 5 Nov 2025 13:25:25 +0000 From: Catalin Marinas To: Yicong Yang Cc: "Paul E. McKenney" , Will Deacon , Mark Rutland , linux-arm-kernel@lists.infradead.org, Willy Tarreau Subject: Re: Overhead of arm64 LSE per-CPU atomics? Message-ID: References: <31847558-db84-4984-ab43-a5f6be00f5eb@paulmck-laptop> <5ab48722-8323-45af-b585-23b34af3017e@paulmck-laptop> <3868c862-cf16-4259-829e-e9004028b3c1@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3868c862-cf16-4259-829e-e9004028b3c1@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251105_052530_308911_37C21309 X-CRM114-Status: GOOD ( 10.76 ) 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 Sat, Nov 01, 2025 at 07:41:02PM +0800, Yicong Yang wrote: > FYI, there's a version to allow prefetech added prior to LSE > opertaions by one boot option [1], if we want to reconsidered in this > way, it's more flexible and can be controlled by the OS without > touching the system configurations (may need to update the firmware). I'm against adding boot time options for this. We either add them permanently if beneficial for most microarchitectures or we get back to the hardware people to ask for improvements (or, potentially, imp def configurations like we have on a few of the Arm Ltd implementations). > But need to add the prefetch in per-cpu implementation as you've > noticed above (didn't add it since no prefetch for LL/SC > implementation there, maybe a missing?) Maybe no-one stressed these to notice any difference between LL/SC and LSE. -- Catalin