linux-kernel - [PATCH] regmap: Reorder 'struct regmap'

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Message-ID: <f01f900d15633d5cda5f27763723acb307c0d22f.1737725820.git.christophe.jaillet@wanadoo.fr>
Date: Fri, 24 Jan 2025 14:37:58 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Mark Brown <broonie@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] regmap: Reorder 'struct regmap'

On a x86_64, with configured with allmodconfig, pahole states that the
regmap structure is:

	/* size: 1048, cachelines: 17, members: 78 */
	/* sum members: 1006, holes: 9, sum holes: 35 */
	/* padding: 7 */
	/* member types with holes: 2, total: 2 */
	/* last cacheline: 24 bytes */

So, when such a struct is allocated, 2048 bytes are allocated, with most of
this space being wasted.

Move a few bools so that the size is reduced to 1024.

After this change, pahole gives:

	/* size: 1024, cachelines: 16, members: 78 */
	/* sum members: 1006, holes: 6, sum holes: 18 */
	/* member types with holes: 2, total: 2 */

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
Compile tested only.

More could be done, to be more future-proof, but the changes would be more
invasive.
---
 drivers/base/regmap/internal.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index bdb450436cbc..6f31240ee4a9 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -73,12 +73,12 @@ struct regmap {
 	void *bus_context;
 	const char *name;
 
-	bool async;
 	spinlock_t async_lock;
 	wait_queue_head_t async_waitq;
 	struct list_head async_list;
 	struct list_head async_free;
 	int async_ret;
+	bool async;
 
 #ifdef CONFIG_DEBUG_FS
 	bool debugfs_disable;
@@ -117,8 +117,6 @@ struct regmap {
 		    void *val_buf, size_t val_size);
 	int (*write)(void *context, const void *data, size_t count);
 
-	bool defer_caching;
-
 	unsigned long read_flag_mask;
 	unsigned long write_flag_mask;
 
@@ -127,6 +125,8 @@ struct regmap {
 	int reg_stride;
 	int reg_stride_order;
 
+	bool defer_caching;
+
 	/* If set, will always write field to HW. */
 	bool force_write_field;
 
@@ -161,6 +161,9 @@ struct regmap {
 	struct reg_sequence *patch;
 	int patch_regs;
 
+	/* if set, the regmap core can sleep */
+	bool can_sleep;
+
 	/* if set, converts bulk read to single read */
 	bool use_single_read;
 	/* if set, converts bulk write to single write */
@@ -176,9 +179,6 @@ struct regmap {
 	void *selector_work_buf;	/* Scratch buffer used for selector */
 
 	struct hwspinlock *hwlock;
-
-	/* if set, the regmap core can sleep */
-	bool can_sleep;
 };
 
 struct regcache_ops {
-- 
2.48.1