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Date: Thu, 10 Apr 2014 19:58:02 -0300
From: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To: <netdev@...r.kernel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <eric.dumazet@...il.com>,
Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
Gregory Clement <gregory.clement@...e-electrons.com>,
Simon Guinot <simon.guinot@...uanux.org>,
Willy Tarreau <w@....eu>, Tawfik Bayouk <tawfik@...vell.com>,
Lior Amsalem <alior@...vell.com>,
Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
Simon Guinot <sguinot@...ie.com>
Subject: [PATCH 3/3] net: mvneta: Introduce a software TSO implementation
This commit implements a software TSO which reduces the CPU
usage significantly while retaining the outbound throughput
at line rate.
Tested on a Plat'home Openblocks AX/3 board acting as iperf client (tx).
The CPU usage shows a substantial CPU usage drop, between 15%-25%.
Other tests performed by Willy Tarreau show performance improvements:
Willy reported that "[..] turning the TSO flag on immediately increases the
HTTP request rate from 1680 to 1820 per second (30 kB objects)".
Tested-by: Willy Tarreau <w@....eu>
Signed-off-by: Simon Guinot <sguinot@...ie.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
---
drivers/net/ethernet/marvell/mvneta.c | 207 +++++++++++++++++++++++++++++++++-
1 file changed, 206 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index e5bd3ca..cd6b998 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -244,6 +244,9 @@
#define MVNETA_TX_MTU_MAX 0x3ffff
+/* TSO header size */
+#define TSO_HEADER_SIZE 128
+
/* Max number of Rx descriptors */
#define MVNETA_MAX_RXD 128
@@ -413,6 +416,12 @@ struct mvneta_tx_queue {
/* Index of the next TX DMA descriptor to process */
int next_desc_to_proc;
+
+ /* DMA buffers for TSO headers */
+ char *tso_hdrs;
+
+ /* DMA address of TSO headers */
+ dma_addr_t tso_hdrs_phys;
};
struct mvneta_rx_queue {
@@ -1519,6 +1528,181 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
return rx_done;
}
+static inline void
+mvneta_tso_build_hdr(struct net_device *dev, struct mvneta_tx_queue *txq,
+ struct sk_buff *skb, int hdr_len, int size,
+ u32 tcp_seq, u16 ip_id, bool is_last)
+{
+ struct mvneta_port *pp = netdev_priv(dev);
+ struct mvneta_tx_desc *tx_desc;
+ struct iphdr *iph;
+ struct tcphdr *tcph;
+ char *mac;
+ int mac_hdr_len = skb_network_offset(skb);
+
+ mac = txq->tso_hdrs + txq->txq_put_index * TSO_HEADER_SIZE;
+ memcpy(mac, skb->data, hdr_len);
+
+ iph = (struct iphdr *)(mac + mac_hdr_len);
+ iph->id = htons(ip_id);
+ iph->tot_len = htons(size + hdr_len - mac_hdr_len);
+
+ tcph = (struct tcphdr *)(mac + skb_transport_offset(skb));
+ tcph->seq = htonl(tcp_seq);
+
+ if (!is_last) {
+ /* Clear all special flags for not last packet */
+ tcph->psh = 0;
+ tcph->fin = 0;
+ tcph->rst = 0;
+ }
+
+ txq->tx_skb[txq->txq_put_index] = NULL;
+ tx_desc = mvneta_txq_next_desc_get(txq);
+ tx_desc->data_size = hdr_len;
+ tx_desc->command = mvneta_skb_tx_csum(pp, skb);
+ tx_desc->command |= MVNETA_TXD_F_DESC;
+ tx_desc->buf_phys_addr = txq->tso_hdrs_phys +
+ txq->txq_put_index * TSO_HEADER_SIZE;
+ mvneta_txq_inc_put(txq);
+}
+
+static inline int
+mvneta_tso_build_data(struct net_device *dev, struct mvneta_tx_queue *txq,
+ struct sk_buff *skb, char *frag_ptr, int frag_size,
+ int data_left, bool is_last)
+{
+ int size;
+ struct mvneta_tx_desc *tx_desc;
+
+ size = (frag_size < data_left) ? frag_size : data_left;
+
+ tx_desc = mvneta_txq_next_desc_get(txq);
+ tx_desc->data_size = size;
+ tx_desc->buf_phys_addr = dma_map_single(dev->dev.parent, frag_ptr,
+ size, DMA_TO_DEVICE);
+ if (unlikely(dma_mapping_error(dev->dev.parent,
+ tx_desc->buf_phys_addr))) {
+ mvneta_txq_desc_put(txq);
+ return 0;
+ }
+
+ tx_desc->command = 0;
+ txq->tx_skb[txq->txq_put_index] = NULL;
+
+ if (size == data_left) {
+ /* last descriptor in the TCP packet */
+ tx_desc->command = MVNETA_TXD_L_DESC;
+
+ /* last descriptor in SKB */
+ if (is_last)
+ txq->tx_skb[txq->txq_put_index] = skb;
+ }
+ mvneta_txq_inc_put(txq);
+ return size;
+}
+
+static int mvneta_tx_tso(struct sk_buff *skb, struct net_device *dev,
+ struct mvneta_tx_queue *txq)
+{
+ int total_len, hdr_len, size, frag_size, data_left;
+ int desc_count;
+ u16 ip_id;
+ u32 tcp_seq;
+ skb_frag_t *frag;
+ int frag_idx = 0;
+ char *frag_ptr;
+ const struct tcphdr *th = tcp_hdr(skb);
+ struct mvneta_port *pp = netdev_priv(dev);
+ int i;
+
+ /* Calculate expected number of TX descriptors */
+ desc_count = skb_shinfo(skb)->gso_segs * 2 + skb_shinfo(skb)->nr_frags;
+ if ((txq->count + desc_count) >= txq->size)
+ return 0;
+
+ total_len = skb->len;
+ hdr_len = (skb_transport_offset(skb) + tcp_hdrlen(skb));
+
+ total_len -= hdr_len;
+ ip_id = ntohs(ip_hdr(skb)->id);
+ tcp_seq = ntohl(th->seq);
+
+ frag_size = skb_headlen(skb);
+ frag_ptr = skb->data;
+
+ if (frag_size < hdr_len)
+ return 0;
+
+ frag_size -= hdr_len;
+ frag_ptr += hdr_len;
+ if (frag_size == 0) {
+ frag = &skb_shinfo(skb)->frags[frag_idx];
+
+ /* Move to next segment */
+ frag_size = frag->size;
+ frag_ptr = page_address(frag->page.p) + frag->page_offset;
+ frag_idx++;
+ }
+ desc_count = 0;
+
+ while (total_len > 0) {
+ data_left = (skb_shinfo(skb)->gso_size < total_len) ?
+ skb_shinfo(skb)->gso_size : total_len;
+ desc_count++;
+ total_len -= data_left;
+
+ /* prepare packet headers: MAC + IP + TCP */
+ mvneta_tso_build_hdr(dev, txq, skb, hdr_len, data_left,
+ tcp_seq, ip_id, total_len == 0);
+ ip_id++;
+
+ while (data_left > 0) {
+ desc_count++;
+
+ size = mvneta_tso_build_data(dev, txq, skb,
+ frag_ptr, frag_size,
+ data_left, total_len == 0);
+ if (size == 0)
+ goto err_release;
+
+ data_left -= size;
+ tcp_seq += size;
+
+ frag_size -= size;
+ frag_ptr += size;
+
+ if ((frag_size == 0) &&
+ (frag_idx < skb_shinfo(skb)->nr_frags)) {
+ frag = &skb_shinfo(skb)->frags[frag_idx];
+
+ /* Move to next segment */
+ frag_size = frag->size;
+ frag_ptr = page_address(frag->page.p) +
+ frag->page_offset;
+ frag_idx++;
+ }
+ }
+ }
+
+ return desc_count;
+
+err_release:
+ /* Release all used data descriptors; header descriptors must not
+ * be DMA-unmapped.
+ */
+ for (i = desc_count - 1; i >= 0; i--) {
+ struct mvneta_tx_desc *tx_desc = txq->descs + i;
+ if (!(tx_desc->command & MVNETA_TXD_F_DESC))
+ dma_unmap_single(pp->dev->dev.parent,
+ tx_desc->buf_phys_addr,
+ tx_desc->data_size,
+ DMA_TO_DEVICE);
+ mvneta_txq_desc_put(txq);
+ }
+ return 0;
+}
+
/* Handle tx fragmentation processing */
static int mvneta_tx_frag_process(struct mvneta_port *pp, struct sk_buff *skb,
struct mvneta_tx_queue *txq)
@@ -1590,6 +1774,11 @@ static int mvneta_tx(struct sk_buff *skb, struct net_device *dev)
if (!netif_running(dev))
goto out;
+ if (skb_is_gso(skb)) {
+ frags = mvneta_tx_tso(skb, dev, txq);
+ goto out;
+ }
+
frags = skb_shinfo(skb)->nr_frags + 1;
/* Get a descriptor for the first part of the packet */
@@ -2108,6 +2297,18 @@ static int mvneta_txq_init(struct mvneta_port *pp,
txq->descs, txq->descs_phys);
return -ENOMEM;
}
+
+ /* Allocate DMA buffers for TSO MAC/IP/TCP headers */
+ txq->tso_hdrs = dma_alloc_coherent(pp->dev->dev.parent,
+ txq->size * TSO_HEADER_SIZE,
+ &txq->tso_hdrs_phys, GFP_KERNEL);
+ if (txq->tso_hdrs == NULL) {
+ kfree(txq->tx_skb);
+ dma_free_coherent(pp->dev->dev.parent,
+ txq->size * MVNETA_DESC_ALIGNED_SIZE,
+ txq->descs, txq->descs_phys);
+ return -ENOMEM;
+ }
mvneta_tx_done_pkts_coal_set(pp, txq, txq->done_pkts_coal);
return 0;
@@ -2119,6 +2320,10 @@ static void mvneta_txq_deinit(struct mvneta_port *pp,
{
kfree(txq->tx_skb);
+ if (txq->tso_hdrs)
+ dma_free_coherent(pp->dev->dev.parent,
+ txq->size * TSO_HEADER_SIZE,
+ txq->tso_hdrs, txq->tso_hdrs_phys);
if (txq->descs)
dma_free_coherent(pp->dev->dev.parent,
txq->size * MVNETA_DESC_ALIGNED_SIZE,
@@ -2861,7 +3066,7 @@ static int mvneta_probe(struct platform_device *pdev)
netif_napi_add(dev, &pp->napi, mvneta_poll, pp->weight);
- dev->features = NETIF_F_SG | NETIF_F_IP_CSUM;
+ dev->features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO;
dev->hw_features |= dev->features;
dev->vlan_features |= dev->features;
dev->priv_flags |= IFF_UNICAST_FLT;
--
1.9.1
--
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