[PATCH net-next] net: sctp: reorder sctp_globals to reduce cacheline usage

[PATCH net-next] net: sctp: reorder sctp_globals to reduce cacheline usage

[Daniel Borkmann]

Reduce cacheline usage from 2 to 1 cacheline for sctp_globals structure. By
reordering elements, we can close gaps and simply achieve the following:

Current situation:
  /* size: 80, cachelines: 2, members: 10 */
  /* sum members: 57, holes: 4, sum holes: 16 */
  /* padding: 7 */
  /* last cacheline: 16 bytes */

Afterwards:
  /* size: 64, cachelines: 1, members: 10 */
  /* padding: 7 */

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
---
 include/net/sctp/structs.h | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 422db6c..2174d8d 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -113,29 +113,27 @@ struct sctp_hashbucket {
 
 /* The SCTP globals structure. */
 extern struct sctp_globals {
-	/* The following variables are implementation specific.	 */
-
-	/* Default initialization values to be applied to new associations. */
-	__u16 max_instreams;
-	__u16 max_outstreams;
-
 	/* This is a list of groups of functions for each address
 	 * family that we support.
 	 */
 	struct list_head address_families;
 
 	/* This is the hash of all endpoints. */
-	int ep_hashsize;
 	struct sctp_hashbucket *ep_hashtable;
-
 	/* This is the hash of all associations. */
-	int assoc_hashsize;
 	struct sctp_hashbucket *assoc_hashtable;
-
 	/* This is the sctp port control hash.	*/
-	int port_hashsize;
 	struct sctp_bind_hashbucket *port_hashtable;
 
+	/* Sizes of above hashtables. */
+	int ep_hashsize;
+	int assoc_hashsize;
+	int port_hashsize;
+
+	/* Default initialization values to be applied to new associations. */
+	__u16 max_instreams;
+	__u16 max_outstreams;
+
 	/* Flag to indicate whether computing and verifying checksum
 	 * is disabled. */
         bool checksum_disable;
-- 
1.7.11.7

Re: [PATCH net-next] net: sctp: reorder sctp_globals to reduce cacheline usage

[Neil Horman]

On Mon, Aug 26, 2013 at 04:34:00PM +0200, Daniel Borkmann wrote:
> Reduce cacheline usage from 2 to 1 cacheline for sctp_globals structure. By
> reordering elements, we can close gaps and simply achieve the following:
> 
> Current situation:
>   /* size: 80, cachelines: 2, members: 10 */
>   /* sum members: 57, holes: 4, sum holes: 16 */
>   /* padding: 7 */
>   /* last cacheline: 16 bytes */
> 
> Afterwards:
>   /* size: 64, cachelines: 1, members: 10 */
>   /* padding: 7 */
> 
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>

Re: [PATCH net-next] net: sctp: reorder sctp_globals to reduce cacheline usage

[David Miller]

From: Daniel Borkmann <dborkman@redhat.com>
Date: Mon, 26 Aug 2013 16:34:00 +0200

> Reduce cacheline usage from 2 to 1 cacheline for sctp_globals structure. By
> reordering elements, we can close gaps and simply achieve the following:
> 
> Current situation:
>   /* size: 80, cachelines: 2, members: 10 */
>   /* sum members: 57, holes: 4, sum holes: 16 */
>   /* padding: 7 */
>   /* last cacheline: 16 bytes */
> 
> Afterwards:
>   /* size: 64, cachelines: 1, members: 10 */
>   /* padding: 7 */
> 
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

Applied.