From 6a321cb370ad3db4ba6e405e638b3a42c41089b0 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 28 Apr 2009 04:43:42 -0700 Subject: [PATCH] net: netif_tx_queue_stopped too expensive netif_tx_queue_stopped(txq) is most of the time false. Yet its cost is very expensive on SMP. static inline int netif_tx_queue_stopped(const struct netdev_queue *dev_queue) { return test_bit(__QUEUE_STATE_XOFF, &dev_queue->state); } I saw this on oprofile hunting and bnx2 driver bnx2_tx_int(). We probably should split "struct netdev_queue" in two parts, one being read mostly. __netif_tx_lock() touches _xmit_lock & xmit_lock_owner, these deserve a separate cache line. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/netdevice.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index f8c3619..505a3c6 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -447,12 +447,18 @@ enum netdev_queue_state_t }; struct netdev_queue { +/* + * read mostly part + */ struct net_device *dev; struct Qdisc *qdisc; unsigned long state; - spinlock_t _xmit_lock; - int xmit_lock_owner; struct Qdisc *qdisc_sleeping; +/* + * write mostly part + */ + spinlock_t _xmit_lock ____cacheline_aligned_in_smp; + int xmit_lock_owner; } ____cacheline_aligned_in_smp; -- 2.7.4