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Message-Id: <bb631974888dfe1af593b6280cf30fb913d2d1a4.1676365116.git.christophe.jaillet@wanadoo.fr>
Date: Tue, 14 Feb 2023 09:58:59 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Lee Jones <lee@...nel.org>
Cc: linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] mfd: core: Reorder fields in 'struct mfd_cell' to save some memory
Group some variables based on their sizes to reduce hole and avoid padding.
On x86_64, this shrinks the size from 144 to 128 bytes.
As an example:
$ size drivers/mfd/as3722.o (Before)
text data bss dec hex filename
9441 680 16 10137 2799 drivers/mfd/as3722.o
$ size drivers/mfd/as3722.o (After)
text data bss dec hex filename
9345 680 16 10041 2739 drivers/mfd/as3722.o
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
Using pahole
Before:
======
struct mfd_cell {
const char * name; /* 0 8 */
int id; /* 8 4 */
int level; /* 12 4 */
int (*enable)(struct platform_device *); /* 16 8 */
int (*disable)(struct platform_device *); /* 24 8 */
int (*suspend)(struct platform_device *); /* 32 8 */
int (*resume)(struct platform_device *); /* 40 8 */
void * platform_data; /* 48 8 */
size_t pdata_size; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
const struct software_node * swnode; /* 64 8 */
const char * of_compatible; /* 72 8 */
const u64 of_reg; /* 80 8 */
bool use_of_reg; /* 88 1 */
/* XXX 7 bytes hole, try to pack */
const struct mfd_cell_acpi_match * acpi_match; /* 96 8 */
int num_resources; /* 104 4 */
/* XXX 4 bytes hole, try to pack */
const struct resource * resources; /* 112 8 */
bool ignore_resource_conflicts; /* 120 1 */
bool pm_runtime_no_callbacks; /* 121 1 */
/* XXX 6 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
const char * const * parent_supplies; /* 128 8 */
int num_parent_supplies; /* 136 4 */
/* size: 144, cachelines: 3, members: 20 */
/* sum members: 123, holes: 3, sum holes: 17 */
/* padding: 4 */
/* last cacheline: 16 bytes */
};
After:
=====
struct mfd_cell {
const char * name; /* 0 8 */
int id; /* 8 4 */
int level; /* 12 4 */
int (*enable)(struct platform_device *); /* 16 8 */
int (*disable)(struct platform_device *); /* 24 8 */
int (*suspend)(struct platform_device *); /* 32 8 */
int (*resume)(struct platform_device *); /* 40 8 */
void * platform_data; /* 48 8 */
size_t pdata_size; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
const struct mfd_cell_acpi_match * acpi_match; /* 64 8 */
const struct software_node * swnode; /* 72 8 */
const char * of_compatible; /* 80 8 */
const u64 of_reg; /* 88 8 */
bool use_of_reg; /* 96 1 */
/* XXX 3 bytes hole, try to pack */
int num_resources; /* 100 4 */
const struct resource * resources; /* 104 8 */
bool ignore_resource_conflicts; /* 112 1 */
bool pm_runtime_no_callbacks; /* 113 1 */
/* XXX 2 bytes hole, try to pack */
int num_parent_supplies; /* 116 4 */
const char * const * parent_supplies; /* 120 8 */
/* size: 128, cachelines: 2, members: 20 */
/* sum members: 123, holes: 2, sum holes: 5 */
};
---
include/linux/mfd/core.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
index 14ca7b471576..fc4a0e9fb3bb 100644
--- a/include/linux/mfd/core.h
+++ b/include/linux/mfd/core.h
@@ -78,6 +78,9 @@ struct mfd_cell {
void *platform_data;
size_t pdata_size;
+ /* Matches ACPI */
+ const struct mfd_cell_acpi_match *acpi_match;
+
/* Software node for the device. */
const struct software_node *swnode;
@@ -97,9 +100,6 @@ struct mfd_cell {
/* Set to 'true' to use 'of_reg' (above) - allows for of_reg=0 */
bool use_of_reg;
- /* Matches ACPI */
- const struct mfd_cell_acpi_match *acpi_match;
-
/*
* These resources can be specified relative to the parent device.
* For accessing hardware you should use resources from the platform dev
@@ -119,8 +119,8 @@ struct mfd_cell {
/* A list of regulator supplies that should be mapped to the MFD
* device rather than the child device when requested
*/
- const char * const *parent_supplies;
int num_parent_supplies;
+ const char * const *parent_supplies;
};
/*
--
2.34.1
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