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ibmveth: Add tx_copybreak

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Use the existing bounce buffer if we send a buffer under a certain size.
This saves the overhead of a TCE map/unmap.

I can't see any reason for the wmb() in the bounce buffer case, if we need
a barrier it will be before we call h_send_logical_lan but we have
nothing in the common case. Remove it.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Santiago Leon <santil@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Santiago Leon 2010-09-03 18:28:20 +00:00 committed by David S. Miller
parent e8cb7eb473
commit c08cc3cceb
1 changed files with 20 additions and 8 deletions
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28
drivers/net/ibmveth.c
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@ -117,6 +117,11 @@ MODULE_DESCRIPTION("IBM i/pSeries Virtual Ethernet Driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(ibmveth_driver_version);
static unsigned int tx_copybreak __read_mostly = 128;
module_param(tx_copybreak, uint, 0644);
MODULE_PARM_DESC(tx_copybreak,
"Maximum size of packet that is copied to a new buffer on transmit");
struct ibmveth_stat {
char name[ETH_GSTRING_LEN];
int offset;
@ -931,17 +936,24 @@ static netdev_tx_t ibmveth_start_xmit(struct sk_buff *skb,
buf[1] = 0;
}
data_dma_addr = dma_map_single(&adapter->vdev->dev, skb->data,
skb->len, DMA_TO_DEVICE);
if (dma_mapping_error(&adapter->vdev->dev, data_dma_addr)) {
if (!firmware_has_feature(FW_FEATURE_CMO))
ibmveth_error_printk("tx: unable to map xmit buffer\n");
if (skb->len < tx_copybreak) {
used_bounce = 1;
} else {
data_dma_addr = dma_map_single(&adapter->vdev->dev, skb->data,
skb->len, DMA_TO_DEVICE);
if (dma_mapping_error(&adapter->vdev->dev, data_dma_addr)) {
if (!firmware_has_feature(FW_FEATURE_CMO))
ibmveth_error_printk("tx: unable to map "
"xmit buffer\n");
tx_map_failed++;
used_bounce = 1;
}
}
if (used_bounce) {
skb_copy_from_linear_data(skb, adapter->bounce_buffer,
skb->len);
desc.fields.address = adapter->bounce_buffer_dma;
tx_map_failed++;
used_bounce = 1;
wmb();
} else
desc.fields.address = data_dma_addr;