linux-kernel - [PATCH] regulator: consumer: Reorder fields in 'struct regulator_bulk

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Date: Sun, 12 May 2024 13:11:21 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] regulator: consumer: Reorder fields in 'struct regulator_bulk_data'

Based on pahole, 2 holes can be combined in 'struct regulator_bulk_data'.

On x86_64 and allmodconfig, this shrinks the size of the structure from 32
to 24 bytes.

This is usually a win, because this structure is often used for static
global variables.

As an example:
Before:
   text	   data	    bss	    dec	    hex	filename
   3557	    162	      0	   3719	    e87	drivers/gpu/drm/msm/dsi/dsi_cfg.o

After:
   text	   data	    bss	    dec	    hex	filename
   3477	    162	      0	   3639	    e37	drivers/gpu/drm/msm/dsi/dsi_cfg.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
Before:
======
struct regulator_bulk_data {
	const char  *              supply;               /*     0     8 */
	int                        init_load_uA;         /*     8     4 */

	/* XXX 4 bytes hole, try to pack */

	struct regulator *         consumer;             /*    16     8 */
	int                        ret;                  /*    24     4 */

	/* size: 32, cachelines: 1, members: 4 */
	/* sum members: 24, holes: 1, sum holes: 4 */
	/* padding: 4 */
	/* last cacheline: 32 bytes */
};

After:
=====
struct regulator_bulk_data {
	const char  *              supply;               /*     0     8 */
	struct regulator *         consumer;             /*     8     8 */
	int                        init_load_uA;         /*    16     4 */
	int                        ret;                  /*    20     4 */

	/* size: 24, cachelines: 1, members: 4 */
	/* last cacheline: 24 bytes */
};
---
 include/linux/regulator/consumer.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/regulator/consumer.h b/include/linux/regulator/consumer.h
index 59d0b9a79e6e..e6f81fc1fb17 100644
--- a/include/linux/regulator/consumer.h
+++ b/include/linux/regulator/consumer.h
@@ -128,11 +128,11 @@ struct regulator;
  *
  * @supply:       The name of the supply.  Initialised by the user before
  *                using the bulk regulator APIs.
+ * @consumer:     The regulator consumer for the supply.  This will be managed
+ *                by the bulk API.
  * @init_load_uA: After getting the regulator, regulator_set_load() will be
  *                called with this load.  Initialised by the user before
  *                using the bulk regulator APIs.
- * @consumer:     The regulator consumer for the supply.  This will be managed
- *                by the bulk API.
  *
  * The regulator APIs provide a series of regulator_bulk_() API calls as
  * a convenience to consumers which require multiple supplies.  This
@@ -140,8 +140,8 @@ struct regulator;
  */
 struct regulator_bulk_data {
 	const char *supply;
-	int init_load_uA;
 	struct regulator *consumer;
+	int init_load_uA;
 
 	/* private: Internal use */
 	int ret;
-- 
2.45.0