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From: Richard Kennedy on 18 Mar 2010 06:30
Remove alignment padding to shrink struct request from 336 to 320 bytes
so needing one fewer cacheline and therefore removing 48 bytes from
struct request_queue.


Signed-off-by: Richard Kennedy <richard(a)rsk.demon.co.uk>
---
patch against 2.6.34-rc1
compiled & tested on x86_64

regards
Richard


diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index ebd22db..6b66438 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -158,7 +158,6 @@ enum rq_flag_bits {
struct request {
struct list_head queuelist;
struct call_single_data csd;
- int cpu;

struct request_queue *q;

@@ -166,9 +165,11 @@ struct request {
enum rq_cmd_type_bits cmd_type;
unsigned long atomic_flags;

+ int cpu;
+
/* the following two fields are internal, NEVER access directly */
- sector_t __sector; /* sector cursor */
unsigned int __data_len; /* total data len */
+ sector_t __sector; /* sector cursor */

struct bio *bio;
struct bio *biotail;
@@ -201,20 +202,20 @@ struct request {

unsigned short ioprio;

+ int ref_count;
+
void *special; /* opaque pointer available for LLD use */
char *buffer; /* kaddr of the current segment if available */

int tag;
int errors;

- int ref_count;
-
/*
* when request is used as a packet command carrier
*/
- unsigned short cmd_len;
unsigned char __cmd[BLK_MAX_CDB];
unsigned char *cmd;
+ unsigned short cmd_len;

unsigned int extra_len; /* length of alignment and padding */
unsigned int sense_len;


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