[PATCH] regmap: Reorder fields in 'struct regmap_bus' to save some memory
From: Christophe JAILLET
Date: Tue Feb 14 2023 - 03:40:54 EST
Group some bool variables to reduce hole and avoid padding.
On x86_64, this shrinks the size from 136 to 128 bytes.
As an example:
$ size drivers/base/regmap/regmap-fsi.o (Before)
text data bss dec hex filename
4837 136 0 4973 136d drivers/base/regmap/regmap-fsi.o
$ size drivers/base/regmap/regmap-fsi.o (After)
text data bss dec hex filename
4701 136 0 4837 12e5 drivers/base/regmap/regmap-fsi.o
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
Using pahole
Before:
======
struct regmap_bus {
bool fast_io; /* 0 1 */
/* XXX 7 bytes hole, try to pack */
regmap_hw_write write; /* 8 8 */
regmap_hw_gather_write gather_write; /* 16 8 */
regmap_hw_async_write async_write; /* 24 8 */
regmap_hw_reg_write reg_write; /* 32 8 */
regmap_hw_reg_noinc_write reg_noinc_write; /* 40 8 */
regmap_hw_reg_update_bits reg_update_bits; /* 48 8 */
regmap_hw_read read; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
regmap_hw_reg_read reg_read; /* 64 8 */
regmap_hw_reg_noinc_read reg_noinc_read; /* 72 8 */
regmap_hw_free_context free_context; /* 80 8 */
regmap_hw_async_alloc async_alloc; /* 88 8 */
u8 read_flag_mask; /* 96 1 */
/* XXX 3 bytes hole, try to pack */
enum regmap_endian reg_format_endian_default; /* 100 4 */
enum regmap_endian val_format_endian_default; /* 104 4 */
/* XXX 4 bytes hole, try to pack */
size_t max_raw_read; /* 112 8 */
size_t max_raw_write; /* 120 8 */
/* --- cacheline 2 boundary (128 bytes) --- */
bool free_on_exit; /* 128 1 */
/* size: 136, cachelines: 3, members: 18 */
/* sum members: 115, holes: 3, sum holes: 14 */
/* padding: 7 */
/* last cacheline: 8 bytes */
};
After:
=====
struct regmap_bus {
bool fast_io; /* 0 1 */
bool free_on_exit; /* 1 1 */
/* XXX 6 bytes hole, try to pack */
regmap_hw_write write; /* 8 8 */
regmap_hw_gather_write gather_write; /* 16 8 */
regmap_hw_async_write async_write; /* 24 8 */
regmap_hw_reg_write reg_write; /* 32 8 */
regmap_hw_reg_noinc_write reg_noinc_write; /* 40 8 */
regmap_hw_reg_update_bits reg_update_bits; /* 48 8 */
regmap_hw_read read; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
regmap_hw_reg_read reg_read; /* 64 8 */
regmap_hw_reg_noinc_read reg_noinc_read; /* 72 8 */
regmap_hw_free_context free_context; /* 80 8 */
regmap_hw_async_alloc async_alloc; /* 88 8 */
u8 read_flag_mask; /* 96 1 */
/* XXX 3 bytes hole, try to pack */
enum regmap_endian reg_format_endian_default; /* 100 4 */
enum regmap_endian val_format_endian_default; /* 104 4 */
/* XXX 4 bytes hole, try to pack */
size_t max_raw_read; /* 112 8 */
size_t max_raw_write; /* 120 8 */
/* size: 128, cachelines: 2, members: 18 */
/* sum members: 115, holes: 3, sum holes: 13 */
};
---
include/linux/regmap.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 029b9e09d3ca..f26432dc02ef 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -520,6 +520,7 @@ typedef void (*regmap_hw_free_context)(void *context);
* to perform locking. This field is ignored if custom lock/unlock
* functions are used (see fields lock/unlock of
* struct regmap_config).
+ * @free_on_exit: kfree this on exit of regmap
* @write: Write operation.
* @gather_write: Write operation with split register/value, return -ENOTSUPP
* if not implemented on a given device.
@@ -548,10 +549,10 @@ typedef void (*regmap_hw_free_context)(void *context);
* DEFAULT, BIG is assumed.
* @max_raw_read: Max raw read size that can be used on the bus.
* @max_raw_write: Max raw write size that can be used on the bus.
- * @free_on_exit: kfree this on exit of regmap
*/
struct regmap_bus {
bool fast_io;
+ bool free_on_exit;
regmap_hw_write write;
regmap_hw_gather_write gather_write;
regmap_hw_async_write async_write;
@@ -568,7 +569,6 @@ struct regmap_bus {
enum regmap_endian val_format_endian_default;
size_t max_raw_read;
size_t max_raw_write;
- bool free_on_exit;
};
/*
--
2.34.1