Messages in this thread Patch in this message | | | From | Christophe JAILLET <> | Subject | [PATCH] clk: Reorder fields in 'struct clk_fractional_divider' | Date | Fri, 17 Feb 2023 16:55:55 +0100 |
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Group some variables based on their sizes to reduce hole and avoid padding. On x86_64, this shrinks the size of 'struct clk_fractional_divider' from 72 to 64 bytes.
It saves a few bytes of memory when the structure is kzalloc()'ed.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- Using pahole
Before: ====== struct clk_fractional_divider { struct clk_hw hw; /* 0 24 */ void * reg; /* 24 8 */ u8 mshift; /* 32 1 */ u8 mwidth; /* 33 1 */
/* XXX 2 bytes hole, try to pack */
u32 mmask; /* 36 4 */ u8 nshift; /* 40 1 */ u8 nwidth; /* 41 1 */
/* XXX 2 bytes hole, try to pack */
u32 nmask; /* 44 4 */ u8 flags; /* 48 1 */
/* XXX 7 bytes hole, try to pack */
void (*approximation)(struct clk_hw *, long unsigned int, long unsigned int *, long unsigned int *, long unsigned int *); /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ spinlock_t * lock; /* 64 8 */
/* size: 72, cachelines: 2, members: 11 */ /* sum members: 61, holes: 3, sum holes: 11 */ /* last cacheline: 8 bytes */ };
After: ===== struct clk_fractional_divider { struct clk_hw hw; /* 0 24 */ void * reg; /* 24 8 */ u8 flags; /* 32 1 */ u8 mshift; /* 33 1 */ u8 mwidth; /* 34 1 */
/* XXX 1 byte hole, try to pack */
u32 mmask; /* 36 4 */ u8 nshift; /* 40 1 */ u8 nwidth; /* 41 1 */
/* XXX 2 bytes hole, try to pack */
u32 nmask; /* 44 4 */ void (*approximation)(struct clk_hw *, long unsigned int, long unsigned int *, long unsigned int *, long unsigned int *); /* 48 8 */ spinlock_t * lock; /* 56 8 */
/* size: 64, cachelines: 1, members: 11 */ /* sum members: 61, holes: 2, sum holes: 3 */ }; --- include/linux/clk-provider.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index cf1adfeaf257..8cec844f5dde 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -1134,13 +1134,13 @@ struct clk_hw *clk_hw_register_fixed_factor_parent_hw(struct device *dev, struct clk_fractional_divider { struct clk_hw hw; void __iomem *reg; + u8 flags; u8 mshift; u8 mwidth; u32 mmask; u8 nshift; u8 nwidth; u32 nmask; - u8 flags; void (*approximation)(struct clk_hw *hw, unsigned long rate, unsigned long *parent_rate, unsigned long *m, unsigned long *n); -- 2.34.1
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