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ibmveth: Add tx_copybreak
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>
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@ -117,6 +117,11 @@ MODULE_DESCRIPTION("IBM i/pSeries Virtual Ethernet Driver");
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MODULE_LICENSE("GPL");
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MODULE_VERSION(ibmveth_driver_version);
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static unsigned int tx_copybreak __read_mostly = 128;
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module_param(tx_copybreak, uint, 0644);
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MODULE_PARM_DESC(tx_copybreak,
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"Maximum size of packet that is copied to a new buffer on transmit");
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struct ibmveth_stat {
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char name[ETH_GSTRING_LEN];
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int offset;
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@ -931,17 +936,24 @@ static netdev_tx_t ibmveth_start_xmit(struct sk_buff *skb,
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buf[1] = 0;
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}
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if (skb->len < tx_copybreak) {
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used_bounce = 1;
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} else {
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data_dma_addr = dma_map_single(&adapter->vdev->dev, skb->data,
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skb->len, DMA_TO_DEVICE);
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if (dma_mapping_error(&adapter->vdev->dev, data_dma_addr)) {
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if (!firmware_has_feature(FW_FEATURE_CMO))
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ibmveth_error_printk("tx: unable to map xmit buffer\n");
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ibmveth_error_printk("tx: unable to map "
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"xmit buffer\n");
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tx_map_failed++;
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used_bounce = 1;
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}
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}
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if (used_bounce) {
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skb_copy_from_linear_data(skb, adapter->bounce_buffer,
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skb->len);
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desc.fields.address = adapter->bounce_buffer_dma;
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tx_map_failed++;
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used_bounce = 1;
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wmb();
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} else
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desc.fields.address = data_dma_addr;
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