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authorEric Dumazet <dada1@cosmosbay.com>2009-04-28 04:43:42 -0700
committerDavid S. Miller <davem@davemloft.net>2009-04-28 04:43:42 -0700
commit6a321cb370ad3db4ba6e405e638b3a42c41089b0 (patch)
tree2e7c25cff76fc6b439afb04e24ab1133e42667b8
parent8555a5948467e941acc34e8b1c30df4c1f2f5862 (diff)
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 <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/linux/netdevice.h10
1 files changed, 8 insertions, 2 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f8c3619d551..505a3c6cb12 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;