Linux Ethernet Bridging - Sep 2018 - [Bridge] [PATCH net-next 9/9] net: bridge: pack net_bridge better

Further reduce the size of net_bridge with 8 bytes and reduce the number of
holes in it:
 Before: holes: 5, sum holes: 15
 After: holes: 2, sum holes: 3

Also as a bonus we get offload_fwd_mark in the first cache line and remove
the need to pull the last cache line of net_bridge just for that member in
fast path (should_deliver -> nbp_switchdev_allowed_egress).

Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
---
 net/bridge/br_private.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 92d08f8c7dd4..e50506225666 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -329,6 +329,9 @@ struct net_bridge {
 	struct net_device		*dev;
 	struct pcpu_sw_netstats		__percpu *stats;
 	unsigned long			options;
+#ifdef CONFIG_NET_SWITCHDEV
+	int offload_fwd_mark;
+#endif
 	/* These fields are accessed on each packet */
 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
 	__be16				vlan_proto;
@@ -349,7 +352,6 @@ struct net_bridge {
 	/* STP */
 	bridge_id			designated_root;
 	bridge_id			bridge_id;
-	u32				root_path_cost;
 	unsigned char			topology_change;
 	unsigned char			topology_change_detected;
 	u16				root_port;
@@ -361,6 +363,7 @@ struct net_bridge {
 	unsigned long			bridge_hello_time;
 	unsigned long			bridge_forward_delay;
 	unsigned long			bridge_ageing_time;
+	u32				root_path_cost;
 
 	u8				group_addr[ETH_ALEN];
 
@@ -383,6 +386,7 @@ struct net_bridge {
 #if IS_ENABLED(CONFIG_IPV6)
 	u8				multicast_mld_version;
 #endif
+	spinlock_t			multicast_lock;
 	unsigned long			multicast_last_member_interval;
 	unsigned long			multicast_membership_interval;
 	unsigned long			multicast_querier_interval;
@@ -390,7 +394,6 @@ struct net_bridge {
 	unsigned long			multicast_query_response_interval;
 	unsigned long			multicast_startup_query_interval;
 
-	spinlock_t			multicast_lock;
 	struct net_bridge_mdb_htable __rcu *mdb;
 	struct hlist_head		router_list;
 
@@ -411,12 +414,9 @@ struct net_bridge {
 	struct timer_list		topology_change_timer;
 	struct delayed_work		gc_work;
 	struct kobject			*ifobj;
-	u32				auto_cnt;
 
-#ifdef CONFIG_NET_SWITCHDEV
-	int offload_fwd_mark;
-#endif
 	struct hlist_head		fdb_list;
+	u32				auto_cnt;
 };
 
 struct br_input_skb_cb {
-- 
2.11.0

On Wed, Sep 26, 2018 at 03:18:02PM +0300, Nikolay Aleksandrov
wrote:
> Further reduce the size of net_bridge with 8 bytes and reduce the number of
> holes in it:
>  Before: holes: 5, sum holes: 15
>  After: holes: 2, sum holes: 3
> 
> Also as a bonus we get offload_fwd_mark in the first cache line and remove
> the need to pull the last cache line of net_bridge just for that member in
> fast path (should_deliver -> nbp_switchdev_allowed_egress).
But nbp_switchdev_allowed_egress() compares with 'offload_fwd_mark' from
'net_bridge_port', not 'net_bridge'...

On 26/09/18 16:30, Ido Schimmel wrote:
> On Wed, Sep 26, 2018 at 03:18:02PM +0300, Nikolay Aleksandrov wrote:
>> Further reduce the size of net_bridge with 8 bytes and reduce the
number of
>> holes in it:
>>  Before: holes: 5, sum holes: 15
>>  After: holes: 2, sum holes: 3
>>
>> Also as a bonus we get offload_fwd_mark in the first cache line and
remove
>> the need to pull the last cache line of net_bridge just for that member
in
>> fast path (should_deliver -> nbp_switchdev_allowed_egress).
> 
> But nbp_switchdev_allowed_egress() compares with 'offload_fwd_mark'
from
> 'net_bridge_port', not 'net_bridge'...
> 
ha, right you are! I need to check my glasses :) Anyway, I'll correct my
commit message and resend v2. We can leave the net_bridge mark in the
end, there're 4 bytes there anyway.

I was thinking of net_bridge_port, but that is a different patch-set I
have. Apparently I've mixed the commit messages.

Thanks!