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authorDavid Laight <David.Laight@ACULAB.COM>2014-07-04 18:35:51 +0400
committerDavid S. Miller <davem@davemloft.net>2014-07-09 01:39:00 +0400
commitb9420e1c87838bcb354ae3495852430413dd9e4b (patch)
treeb0dd1a9022cf37626cd70cdc5f15f7c8507b7647 /include/net/sctp/command.h
parentbe1f4f48cef17c6ea9350db04c774dc8eb252158 (diff)
downloadlinux-b9420e1c87838bcb354ae3495852430413dd9e4b.tar.xz
net: sctp: Optimise the way 'sctp_arg_t' values are initialised.
Even if memset() is inlined (as on x86) using it to zero the union generates a memory word write of zero, followed by a write of the smaller field, and then a read of the word. As well as being a lot of instructions the sequence is unlikely to be optimised by the store-load forward hardware so will be slow. Instead allocate a field of the union that is the same size as the entire union and write a zero value to it. The compiler will then generate the required value in a register. Zeroing the union shouldn't be necessary, but this patch series isn't intended to have a behavioural change. Signed-off-by: David Laight <david.laight@aculab.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/sctp/command.h')
-rw-r--r--include/net/sctp/command.h8
1 files changed, 5 insertions, 3 deletions
diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h
index 0e91a42065db..589a1918ad55 100644
--- a/include/net/sctp/command.h
+++ b/include/net/sctp/command.h
@@ -118,6 +118,7 @@ typedef enum {
#define SCTP_MAX_NUM_COMMANDS 14
typedef union {
+ void *zero_all; /* Set to NULL to clear the entire union */
__s32 i32;
__u32 u32;
__be32 be32;
@@ -154,7 +155,7 @@ typedef union {
static inline sctp_arg_t \
SCTP_## name (type arg) \
{ sctp_arg_t retval;\
- memset(&retval, 0, sizeof(sctp_arg_t));\
+ retval.zero_all = NULL;\
retval.elt = arg;\
return retval;\
}
@@ -191,7 +192,7 @@ static inline sctp_arg_t SCTP_NOFORCE(void)
static inline sctp_arg_t SCTP_NULL(void)
{
sctp_arg_t retval;
- memset(&retval, 0, sizeof(sctp_arg_t));
+ retval.zero_all = NULL;
return retval;
}
@@ -212,7 +213,8 @@ typedef struct {
*/
static inline int sctp_init_cmd_seq(sctp_cmd_seq_t *seq)
{
- memset(seq, 0, sizeof(sctp_cmd_seq_t));
+ seq->next_free_slot = 0;
+ seq->next_cmd = 0;
return 1; /* We always succeed. */
}