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 X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C3CC0C10F0E for ; Fri, 12 Apr 2019 09:52:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9FFCA20850 for ; Fri, 12 Apr 2019 09:52:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726898AbfDLJwu (ORCPT ); Fri, 12 Apr 2019 05:52:50 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:56578 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726694AbfDLJwu (ORCPT ); Fri, 12 Apr 2019 05:52:50 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D7EF415AB; Fri, 12 Apr 2019 02:52:49 -0700 (PDT) Received: from fuggles.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5B9553F59C; Fri, 12 Apr 2019 02:52:48 -0700 (PDT) Date: Fri, 12 Apr 2019 10:52:43 +0100 From: Will Deacon To: Zhangshaokun Cc: Ard Biesheuvel , linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, ilias.apalodimas@linaro.org, "huanglingyan (A)" , steve.capper@arm.com, robin.murphy@arm.com Subject: Re: [PATCH] arm64: do_csum: implement accelerated scalar version Message-ID: <20190412095243.GA27193@fuggles.cambridge.arm.com> References: <20190218230842.11448-1-ard.biesheuvel@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Apr 12, 2019 at 10:31:16AM +0800, Zhangshaokun wrote: > On 2019/2/19 7:08, Ard Biesheuvel wrote: > > It turns out that the IP checksumming code is still exercised often, > > even though one might expect that modern NICs with checksum offload > > have no use for it. However, as Lingyan points out, there are > > combinations of features where the network stack may still fall back > > to software checksumming, and so it makes sense to provide an > > optimized implementation in software as well. > > > > So provide an implementation of do_csum() in scalar assembler, which, > > unlike C, gives direct access to the carry flag, making the code run > > substantially faster. The routine uses overlapping 64 byte loads for > > all input size > 64 bytes, in order to reduce the number of branches > > and improve performance on cores with deep pipelines. > > > > On Cortex-A57, this implementation is on par with Lingyan's NEON > > implementation, and roughly 7x as fast as the generic C code. > > > > Cc: "huanglingyan (A)" > > Signed-off-by: Ard Biesheuvel > > --- > > Test code after the patch. > > Hi maintainers and Ard, > > Any update on it? I'm waiting for Robin to come back with numbers for a C implementation. Robin -- did you get anywhere with that? Will