| Message ID | 49F6CD24.5080000@cosmosbay.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Eric Dumazet <dada1@cosmosbay.com> Date: Tue, 28 Apr 2009 11:32:20 +0200 > netif_tx_queue_stopped(txq) is most of the time false. > > Yet its cost is very expensive on SMP. ... > Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Fair enough, applied to net-next-2.6, thanks Eric. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 2e7783f..1caaebb 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;
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> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html