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Subject[PATCH] use mmiowb in tg3_poll

Returning from tg3_poll() without flushing the PIO write which
reenables interrupts can result in lower cpu utilization and higher
throughput. So use a memory barrier, mmiowb(), instead of flushing the
write with a PIO read.

Signed-off-by: Arthur Kepner <akepner@sgi.com>
---

--- linux-2.6.9-rc4-mm1.orig/drivers/net/tg3.c 2004-10-22 13:51:10.000000000 -0700
+++ linux-2.6.9-rc4-mm1/drivers/net/tg3.c 2004-10-22 13:53:36.000000000 -0700
@@ -417,6 +417,20 @@
tg3_cond_int(tp);
}

+/* tg3_restart_ints
+ * similar to tg3_enable_ints, but it can return without flushing the
+ * PIO write which reenables interrupts
+ */
+static void tg3_restart_ints(struct tg3 *tp)
+{
+ tw32(TG3PCI_MISC_HOST_CTRL,
+ (tp->misc_host_ctrl & ~MISC_HOST_CTRL_MASK_PCI_INT));
+ tw32_mailbox(MAILBOX_INTERRUPT_0 + TG3_64BIT_REG_LOW, 0x00000000);
+ mmiowb();
+
+ tg3_cond_int(tp);
+}
+
static inline void tg3_netif_stop(struct tg3 *tp)
{
netif_poll_disable(tp->dev);
@@ -2787,7 +2801,7 @@
if (done) {
spin_lock_irqsave(&tp->lock, flags);
__netif_rx_complete(netdev);
- tg3_enable_ints(tp);
+ tg3_restart_ints(tp);
spin_unlock_irqrestore(&tp->lock, flags);
}


--
Arthur





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