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 3E1F8C61D9B for ; Wed, 22 Nov 2023 09:49:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To: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=B5McaOtAas0K/vQz8VlCbpauROAsyJU115K0DphFC04=; b=TQY09GOsOGWMB+ 2TC1PNoj8dXoG7T5XjprvyHwq/hP4td0+B7zoOIsBNC3+3Z2dtgukgz2BMisZAC8a7L5r/vpX5cbN wXWcFUF3sDfA+XVO/hOpvfe60q9WtXSZjm0KrTC8uWdJwRP2BhyL03oSIe875HoqOaQKUfhTbhNOQ 1Gtp6CSQ2MSWJ/UWRBCnpDRH/vWGGf58Clbn3rDKHB3x/HqFvkkDTtW/hFy1U8mottw2sG6bnUOyK +fNAkmx4v4xw3dw8/u6lVXKXCQNcm9TOpYzUf+NY3JpFWwAWIzIaCEyVhvlidhMH1k6SMDnRKzeKd nY7JuIUiuK419raGt67Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1r5jr8-001LUZ-1r; Wed, 22 Nov 2023 09:49:14 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1r5jqz-001LJR-2n for linux-arm-kernel@lists.infradead.org; Wed, 22 Nov 2023 09:49:07 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by ams.source.kernel.org (Postfix) with ESMTP id C9029B811A1; Wed, 22 Nov 2023 09:49:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0048C433CB; Wed, 22 Nov 2023 09:49:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1700646543; bh=HquTgPuZlA4Yd/i15aPhlrVGsHZcZNtBHiTfzoBfy24=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=I7U8cpjF5LN+Br7G9Bfg6N2BL/ceOCkIYMQ+CUFRDVjQhiF8BsTxZfTW89k7TKlm/ CdD4+fAwkVRkZRzvcYqsA6lJYvWgMzEF/pcbEdIzXoqfgY6MHic7G67nPmuhoC0yNy O1KwSEXIKxPpTNxZxIDPVu4FFnaPkj5cfsoNwI72bQjsK/rwy/E+3+j20AVZO0E2m9 w6LTT++PeHx7h/9cgJ727JFaX7KmQC2r0kwK+bs2be9QNPySg7oA4jbbcA8YzXoOJ7 UC1uJGnY9iE6B8Q/rtgufLehrmwIl4p2QkRHFxOS4dCT5Wj3qrgzVbhkS4aTOL/Ry2 fcFjdc5RVYSPA== Date: Wed, 22 Nov 2023 09:48:57 +0000 From: Will Deacon To: Huang Shijie Cc: catalin.marinas@arm.com, mark.rutland@arm.com, suzuki.poulose@arm.com, broonie@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, anshuman.khandual@arm.com, robh@kernel.org, oliver.upton@linux.dev, maz@kernel.org, patches@amperecomputing.com Subject: Re: [PATCH 0/4] arm64: an optimization for AmpereOne Message-ID: <20231122094857.GA2959@willie-the-truck> References: <20231122092855.4440-1-shijie@os.amperecomputing.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20231122092855.4440-1-shijie@os.amperecomputing.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231122_014906_090968_953EB7E2 X-CRM114-Status: UNSURE ( 9.95 ) X-CRM114-Notice: Please train this message. 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Nov 22, 2023 at 05:28:51PM +0800, Huang Shijie wrote: > 0) Background: > We found that AmpereOne benefits from aggressive prefetches when > using 4K page size. We tend to shy away from micro-architecture specific optimisations in the arm64 kernel as they're pretty unmaintainable, hard to test properly, generally lead to bloat and add additional obstacles to updating our library routines. Admittedly, we have something for Thunder-X1 in copy_page() (disguised as ARM64_HAS_NO_HW_PREFETCH) but, frankly, that machine needed all the help it could get and given where it is today I suspect we could drop that code without any material consequences. So I'd really prefer not to merge this; modern CPUs should do better at copying data. It's copy_to_user(), not rocket science. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel