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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3631C77B76 for ; Mon, 17 Apr 2023 19:26:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230488AbjDQT0X (ORCPT ); Mon, 17 Apr 2023 15:26:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230465AbjDQT0U (ORCPT ); Mon, 17 Apr 2023 15:26:20 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 448C87A91 for ; Mon, 17 Apr 2023 12:26:18 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id CB990624AB for ; Mon, 17 Apr 2023 19:26:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3FD7C4339B; Mon, 17 Apr 2023 19:26:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1681759577; bh=x7RT5DmwA0MN1byo3Vn7b8wi7XhNBsENhrYQRgalGpc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=OCskGTGYtwKdGfGqvGUzmlTh4aS/6cGVs8v3I7mB/f95wOS+3fPdbFZ1WhRZH0d+N Vpj9NSJlsF9MMawqr8oEfzDvMru0rjtcsgzPtdgbrh3yLjEY7/9orSL/2nGZU+TOEY oPqsjvb/WGrhuD3gWjQiTt4xpllcRtnOo9lr2ahZJTTRQtN9npsNV8LUhgfauHvVkE 09ofZKPb01OAbdXz6O1eHtYhoQcOY8rSDgL/7XKhYZX6q4ER7SiBdoCQG48ZKKSfzp Ofqer+eo0eQzQRKX+lKmi3vSTYjYV9U2oyQCD4byolBz7VqjqqjlctchonbLPI1ABo hRziWkQUX9sxA== Date: Mon, 17 Apr 2023 12:26:16 -0700 From: Jakub Kicinski To: davem@davemloft.net Cc: netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com Subject: Re: [PATCH net-next v2 0/5] net: skbuff: hide some bitfield members Message-ID: <20230417122616.230880c1@kernel.org> In-Reply-To: <20230417155350.337873-1-kuba@kernel.org> References: <20230417155350.337873-1-kuba@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, 17 Apr 2023 08:53:45 -0700 Jakub Kicinski wrote: > There is a number of protocol or subsystem specific fields > in struct sk_buff which are only accessed by one subsystem. > We can wrap them in ifdefs with minimal code impact. > > This gives us a better chance to save a 2B and a 4B holes > resulting with the following savings (assuming a lucky > kernel config): > > - /* size: 232, cachelines: 4, members: 28 */ > - /* sum members: 227, holes: 1, sum holes: 4 */ > - /* sum bitfield members: 8 bits (1 bytes) */ > + /* size: 224, cachelines: 4, members: 28 */ > /* forced alignments: 2 */ > - /* last cacheline: 40 bytes */ > + /* last cacheline: 32 bytes */ > > I think that the changes shouldn't be too controversial. > The only one I'm not 100% sure of is the SCTP one, > 12 extra LoC for one bit.. But it did fit squarely > in the "this bit has only one user" category. Missed Simon's tag, sorry about that: https://lore.kernel.org/all/ZD03APYJqdhflYNJ@kernel.org/ Acked-by: Simon Horman