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 7DCD8C678D4 for ; Wed, 1 Mar 2023 20:59:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229764AbjCAU7E (ORCPT ); Wed, 1 Mar 2023 15:59:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34078 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229704AbjCAU67 (ORCPT ); Wed, 1 Mar 2023 15:58:59 -0500 Received: from smtp.smtpout.orange.fr (smtp-24.smtpout.orange.fr [80.12.242.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F9344E5C7 for ; Wed, 1 Mar 2023 12:58:56 -0800 (PST) Received: from pop-os.home ([86.243.2.178]) by smtp.orange.fr with ESMTPA id XTXKp7HLjYdrCXTXKp7FeZ; Wed, 01 Mar 2023 21:58:55 +0100 X-ME-Helo: pop-os.home X-ME-Auth: Y2hyaXN0b3BoZS5qYWlsbGV0QHdhbmFkb28uZnI= X-ME-Date: Wed, 01 Mar 2023 21:58:55 +0100 X-ME-IP: 86.243.2.178 From: Christophe JAILLET To: Mark Brown Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Christophe JAILLET , linux-spi@vger.kernel.org Subject: [PATCH] spi: Reorder fields in 'struct spi_message' Date: Wed, 1 Mar 2023 21:58:52 +0100 Message-Id: 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 from 112 to 96 bytes. This should have no real impact on memory allocation because 'struct spi_message' is mostly used on stack, but it can save a few cycles when the structure is initialized with spi_message_init() and co. Signed-off-by: Christophe JAILLET --- Using pahole Before: ====== struct spi_message { struct list_head transfers; /* 0 16 */ struct spi_device * spi; /* 16 8 */ unsigned int is_dma_mapped:1; /* 24: 0 4 */ /* XXX 31 bits hole, try to pack */ /* XXX 4 bytes hole, try to pack */ void (*complete)(void *); /* 32 8 */ void * context; /* 40 8 */ unsigned int frame_length; /* 48 4 */ unsigned int actual_length; /* 52 4 */ int status; /* 56 4 */ /* XXX 4 bytes hole, try to pack */ /* --- cacheline 1 boundary (64 bytes) --- */ struct list_head queue; /* 64 16 */ void * state; /* 80 8 */ struct list_head resources; /* 88 16 */ bool prepared; /* 104 1 */ /* size: 112, cachelines: 2, members: 12 */ /* sum members: 93, holes: 2, sum holes: 8 */ /* sum bitfield members: 1 bits, bit holes: 1, sum bit holes: 31 bits */ /* padding: 7 */ /* last cacheline: 48 bytes */ }; After: ===== struct spi_message { struct list_head transfers; /* 0 16 */ struct spi_device * spi; /* 16 8 */ unsigned int is_dma_mapped:1; /* 24: 0 4 */ /* XXX 7 bits hole, try to pack */ /* Bitfield combined with next fields */ bool prepared; /* 25 1 */ /* XXX 2 bytes hole, try to pack */ int status; /* 28 4 */ void (*complete)(void *); /* 32 8 */ void * context; /* 40 8 */ unsigned int frame_length; /* 48 4 */ unsigned int actual_length; /* 52 4 */ struct list_head queue; /* 56 16 */ /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */ void * state; /* 72 8 */ struct list_head resources; /* 80 16 */ /* size: 96, cachelines: 2, members: 12 */ /* sum members: 93, holes: 1, sum holes: 2 */ /* sum bitfield members: 1 bits, bit holes: 1, sum bit holes: 7 bits */ /* last cacheline: 32 bytes */ }; --- include/linux/spi/spi.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 4fa26b9a3572..bdb35a91b4bf 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -1093,6 +1093,9 @@ struct spi_message { unsigned is_dma_mapped:1; + /* spi_prepare_message() was called for this message */ + bool prepared; + /* REVISIT: we might want a flag affecting the behavior of the * last transfer ... allowing things like "read 16 bit length L" * immediately followed by "read L bytes". Basically imposing @@ -1105,11 +1108,11 @@ struct spi_message { */ /* Completion is reported through a callback */ + int status; void (*complete)(void *context); void *context; unsigned frame_length; unsigned actual_length; - int status; /* For optional use by whatever driver currently owns the * spi_message ... between calls to spi_async and then later @@ -1120,9 +1123,6 @@ struct spi_message { /* List of spi_res reources when the spi message is processed */ struct list_head resources; - - /* spi_prepare_message() was called for this message */ - bool prepared; }; static inline void spi_message_init_no_memset(struct spi_message *m) -- 2.34.1