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 47CEDEB64D8 for ; Sun, 18 Jun 2023 09:34:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229748AbjFRJeI (ORCPT ); Sun, 18 Jun 2023 05:34:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43582 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229737AbjFRJeF (ORCPT ); Sun, 18 Jun 2023 05:34:05 -0400 Received: from smtp.smtpout.orange.fr (smtp-21.smtpout.orange.fr [80.12.242.21]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F71710E9 for ; Sun, 18 Jun 2023 02:34:04 -0700 (PDT) Received: from pop-os.home ([86.243.2.178]) by smtp.orange.fr with ESMTPA id AonGq59X5yzHXAonGqVxjA; Sun, 18 Jun 2023 11:34:02 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=wanadoo.fr; s=t20230301; t=1687080842; bh=aVg/k7ynCstaMz721k7lr6Az8vrDxOwyA02xIprHpec=; h=From:To:Cc:Subject:Date; b=keWNbqPt6AoeSWh7bs0Pxc+aVdWPLZihbxi3uZ+XUbPzMsUNtqINXjqOgyJ8qdvuM pcK9hR088E5/XTA3d6vgBqU5slH+OcbJb8az1qqaXr3Lt5xpMn0ef9OdIypuGicH+F rlFL5ugkrNZFqMAesArycjeaquu1kN4m6GgaRagFZNsnaUnbvXPSFvlB6NU3p4/BL/ 00/Zu77MKIj3V4YBLlg3RZi/JFf9Gq8SVWHxP7cP0ruyC38+Nn8s+EfyAUTFSLBfJF Aj/ic/1BOodkREUsim9RHfshFBPD6RBfZElx8JX1hU9eCDVCJEIwFYPORCIZmnEI1X wyty99C5Ebpqw== X-ME-Helo: pop-os.home X-ME-Auth: Y2hyaXN0b3BoZS5qYWlsbGV0QHdhbmFkb28uZnI= X-ME-Date: Sun, 18 Jun 2023 11:34:02 +0200 X-ME-IP: 86.243.2.178 From: Christophe JAILLET To: Jeremy Kerr , Matt Johnston , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Christophe JAILLET , netdev@vger.kernel.org Subject: [PATCH net-next] mctp: Reorder fields in 'struct mctp_route' Date: Sun, 18 Jun 2023 11:33:55 +0200 Message-Id: <393ad1a5aef0aa28d839eeb3d7477da0e0eeb0b0.1687080803.git.christophe.jaillet@wanadoo.fr> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Group some variables based on their sizes to reduce hole and avoid padding. On x86_64, this shrinks the size of 'struct mctp_route' from 72 to 64 bytes. It saves a few bytes of memory and is more cache-line friendly. Signed-off-by: Christophe JAILLET --- Using pahole Before: ====== struct mctp_route { mctp_eid_t min; /* 0 1 */ mctp_eid_t max; /* 1 1 */ /* XXX 6 bytes hole, try to pack */ struct mctp_dev * dev; /* 8 8 */ unsigned int mtu; /* 16 4 */ unsigned char type; /* 20 1 */ /* XXX 3 bytes hole, try to pack */ int (*output)(struct mctp_route *, struct sk_buff *); /* 24 8 */ struct list_head list; /* 32 16 */ refcount_t refs; /* 48 4 */ /* XXX 4 bytes hole, try to pack */ struct callback_head rcu __attribute__((__aligned__(8))); /* 56 16 */ /* size: 72, cachelines: 2, members: 9 */ /* sum members: 59, holes: 3, sum holes: 13 */ /* forced alignments: 1, forced holes: 1, sum forced holes: 4 */ /* last cacheline: 8 bytes */ } __attribute__((__aligned__(8))); After: ===== struct mctp_route { mctp_eid_t min; /* 0 1 */ mctp_eid_t max; /* 1 1 */ unsigned char type; /* 2 1 */ /* XXX 1 byte hole, try to pack */ unsigned int mtu; /* 4 4 */ struct mctp_dev * dev; /* 8 8 */ int (*output)(struct mctp_route *, struct sk_buff *); /* 16 8 */ struct list_head list; /* 24 16 */ refcount_t refs; /* 40 4 */ /* XXX 4 bytes hole, try to pack */ struct callback_head rcu __attribute__((__aligned__(8))); /* 48 16 */ /* size: 64, cachelines: 1, members: 9 */ /* sum members: 59, holes: 2, sum holes: 5 */ /* forced alignments: 1, forced holes: 1, sum forced holes: 4 */ } __attribute__((__aligned__(8))); --- include/net/mctp.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/net/mctp.h b/include/net/mctp.h index 82800d521c3d..da86e106c91d 100644 --- a/include/net/mctp.h +++ b/include/net/mctp.h @@ -234,9 +234,9 @@ struct mctp_flow { struct mctp_route { mctp_eid_t min, max; - struct mctp_dev *dev; - unsigned int mtu; unsigned char type; + unsigned int mtu; + struct mctp_dev *dev; int (*output)(struct mctp_route *route, struct sk_buff *skb); -- 2.34.1