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net: mvneta: implement rx_copybreak

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calling dma_map_single()/dma_unmap_single() is quite expensive compared
to copying a small packet. So let's copy short frames and keep the buffers
mapped. We set the limit to 256 bytes which seems to give good results both
on the XP-GP board and on the AX3/4.

The Rx small packet rate increased by 16.4% doing this, from 486kpps to
573kpps. It is worth noting that even the call to the function
dma_sync_single_range_for_cpu() is expensive (300 ns) although less
than dma_unmap_single(). Without it, the packet rate raises to 711kpps
(+24% more). Thus on systems where coherency from device to CPU is
guaranteed by a snoop control unit, this patch should provide even more
gains, and probably rx_copybreak could be increased.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
willy tarreau 2014-01-16 08:20:17 +01:00 committed by David S. Miller
parent 8ec2cd48fe
commit f19fadfce8
1 changed files with 38 additions and 6 deletions
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44
drivers/net/ethernet/marvell/mvneta.c
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@ -444,6 +444,8 @@ static int txq_number = 8;
static int rxq_def;
static int rx_copybreak __read_mostly = 256;
#define MVNETA_DRIVER_NAME "mvneta"
#define MVNETA_DRIVER_VERSION "1.0"
@ -1463,22 +1465,51 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
rx_done++;
rx_filled++;
rx_status = rx_desc->status;
rx_bytes = rx_desc->data_size - (ETH_FCS_LEN + MVNETA_MH_SIZE);
data = (unsigned char *)rx_desc->buf_cookie;
if (!mvneta_rxq_desc_is_first_last(rx_status) ||
(rx_status & MVNETA_RXD_ERR_SUMMARY) ||
!(skb = build_skb(data, pp->frag_size > PAGE_SIZE ? 0 : pp->frag_size))) {
(rx_status & MVNETA_RXD_ERR_SUMMARY)) {
err_drop_frame:
dev->stats.rx_errors++;
mvneta_rx_error(pp, rx_desc);
/* leave the descriptor untouched */
continue;
}
dma_unmap_single(pp->dev->dev.parent, rx_desc->buf_phys_addr,
if (rx_bytes <= rx_copybreak) {
/* better copy a small frame and not unmap the DMA region */
skb = netdev_alloc_skb_ip_align(dev, rx_bytes);
if (unlikely(!skb))
goto err_drop_frame;
dma_sync_single_range_for_cpu(dev->dev.parent,
rx_desc->buf_phys_addr,
MVNETA_MH_SIZE + NET_SKB_PAD,
rx_bytes,
DMA_FROM_DEVICE);
memcpy(skb_put(skb, rx_bytes),
data + MVNETA_MH_SIZE + NET_SKB_PAD,
rx_bytes);
skb->protocol = eth_type_trans(skb, dev);
mvneta_rx_csum(pp, rx_status, skb);
napi_gro_receive(&pp->napi, skb);
rcvd_pkts++;
rcvd_bytes += rx_bytes;
/* leave the descriptor and buffer untouched */
continue;
}
skb = build_skb(data, pp->frag_size > PAGE_SIZE ? 0 : pp->frag_size);
if (!skb)
goto err_drop_frame;
dma_unmap_single(dev->dev.parent, rx_desc->buf_phys_addr,
MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE);
rx_bytes = rx_desc->data_size -
(ETH_FCS_LEN + MVNETA_MH_SIZE);
rcvd_pkts++;
rcvd_bytes += rx_bytes;
@ -1495,7 +1526,7 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
/* Refill processing */
err = mvneta_rx_refill(pp, rx_desc);
if (err) {
netdev_err(pp->dev, "Linux processing - Can't refill\n");
netdev_err(dev, "Linux processing - Can't refill\n");
rxq->missed++;
rx_filled--;
}
@ -2945,3 +2976,4 @@ module_param(rxq_number, int, S_IRUGO);
module_param(txq_number, int, S_IRUGO);
module_param(rxq_def, int, S_IRUGO);
module_param(rx_copybreak, int, S_IRUGO | S_IWUSR);