[PATCH] ACPI: EC: Reorder fields in 'struct acpi_ec'

[Christophe JAILLET]

Group some variables based on their sizes to reduce hole and avoid padding.
On x86_64, this shrinks the size of 'struct acpi_ec'
from 520 to 512 bytes.

This size is much better when the struct is kmalloc()'ed.

Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
Using pahole

Before:
======
struct acpi_ec {
	acpi_handle                handle;               /*     0     8 */
	acpi_handle                address_space_handler_holder; /*     8     8 */
	int                        gpe;                  /*    16     4 */
	int                        irq;                  /*    20     4 */
	long unsigned int          command_addr;         /*    24     8 */
	long unsigned int          data_addr;            /*    32     8 */
	bool                       global_lock;          /*    40     1 */

	/* XXX 7 bytes hole, try to pack */

	long unsigned int          flags;                /*    48     8 */
	long unsigned int          reference_count;      /*    56     8 */
	/* --- cacheline 1 boundary (64 bytes) --- */
	struct mutex               mutex;                /*    64   160 */
	/* --- cacheline 3 boundary (192 bytes) was 32 bytes ago --- */
	wait_queue_head_t          wait;                 /*   224    88 */
	/* --- cacheline 4 boundary (256 bytes) was 56 bytes ago --- */
	struct list_head           list;                 /*   312    16 */
	/* --- cacheline 5 boundary (320 bytes) was 8 bytes ago --- */
	struct transaction *       curr;                 /*   328     8 */
	spinlock_t                 lock;                 /*   336    72 */
	/* --- cacheline 6 boundary (384 bytes) was 24 bytes ago --- */
	struct work_struct         work;                 /*   408    80 */
	/* --- cacheline 7 boundary (448 bytes) was 40 bytes ago --- */
	long unsigned int          timestamp;            /*   488     8 */
	enum acpi_ec_event_state   event_state;          /*   496     4 */
	unsigned int               events_to_process;    /*   500     4 */
	unsigned int               events_in_progress;   /*   504     4 */
	unsigned int               queries_in_progress;  /*   508     4 */
	/* --- cacheline 8 boundary (512 bytes) --- */
	bool                       busy_polling;         /*   512     1 */

	/* XXX 3 bytes hole, try to pack */

	unsigned int               polling_guard;        /*   516     4 */

	/* size: 520, cachelines: 9, members: 22 */
	/* sum members: 510, holes: 2, sum holes: 10 */
	/* last cacheline: 8 bytes */
};


After:
=====
struct acpi_ec {
	acpi_handle                handle;               /*     0     8 */
	acpi_handle                address_space_handler_holder; /*     8     8 */
	int                        gpe;                  /*    16     4 */
	int                        irq;                  /*    20     4 */
	long unsigned int          command_addr;         /*    24     8 */
	long unsigned int          data_addr;            /*    32     8 */
	bool                       global_lock;          /*    40     1 */
	bool                       busy_polling;         /*    41     1 */

	/* XXX 2 bytes hole, try to pack */

	unsigned int               polling_guard;        /*    44     4 */
	long unsigned int          flags;                /*    48     8 */
	long unsigned int          reference_count;      /*    56     8 */
	/* --- cacheline 1 boundary (64 bytes) --- */
	struct mutex               mutex;                /*    64   160 */
	/* --- cacheline 3 boundary (192 bytes) was 32 bytes ago --- */
	wait_queue_head_t          wait;                 /*   224    88 */
	/* --- cacheline 4 boundary (256 bytes) was 56 bytes ago --- */
	struct list_head           list;                 /*   312    16 */
	/* --- cacheline 5 boundary (320 bytes) was 8 bytes ago --- */
	struct transaction *       curr;                 /*   328     8 */
	spinlock_t                 lock;                 /*   336    72 */
	/* --- cacheline 6 boundary (384 bytes) was 24 bytes ago --- */
	struct work_struct         work;                 /*   408    80 */
	/* --- cacheline 7 boundary (448 bytes) was 40 bytes ago --- */
	long unsigned int          timestamp;            /*   488     8 */
	enum acpi_ec_event_state   event_state;          /*   496     4 */
	unsigned int               events_to_process;    /*   500     4 */
	unsigned int               events_in_progress;   /*   504     4 */
	unsigned int               queries_in_progress;  /*   508     4 */

	/* size: 512, cachelines: 8, members: 22 */
	/* sum members: 510, holes: 1, sum holes: 2 */
};
---
 drivers/acpi/internal.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 06ad497067ac..acfdd23c8dec 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -179,6 +179,8 @@ struct acpi_ec {
 	unsigned long command_addr;
 	unsigned long data_addr;
 	bool global_lock;
+	bool busy_polling;
+	unsigned int polling_guard;
 	unsigned long flags;
 	unsigned long reference_count;
 	struct mutex mutex;
@@ -192,8 +194,6 @@ struct acpi_ec {
 	unsigned int events_to_process;
 	unsigned int events_in_progress;
 	unsigned int queries_in_progress;
-	bool busy_polling;
-	unsigned int polling_guard;
 };
 
 extern struct acpi_ec *first_ec;
-- 
2.34.1