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Date: Fri, 14 Dec 2018 10:59:01 +0200
From: Ilias Apalodimas <ilias.apalodimas@...aro.org>
To: netdev@...r.kernel.org, jaswinder.singh@...aro.org,
ard.biesheuvel@...aro.org
Cc: masami.hiramatsu@...aro.org, masahisa.kojima@...aro.org,
Ilias Apalodimas <ilias.apalodimas@...aro.org>
Subject: [net-next, PATCH 2/2] net: socionext: remove mmio reads on Tx
Currently the driver issues 2 mmio reads to figure out the number of
transmitted packets and clean them. We can get rid of the expensive
reads since BIT 31 of the Tx descriptor can be used for that.
We can also remove the budget counting of Tx completions since all of
the descriptors are not deliberately processed.
Performance numbers using pktgen are:
size pre-patch(pps) post-patch(pps)
64 362483 427916
128 358315 411686
256 352725 389683
512 215675 216464
1024 113812 114442
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
---
drivers/net/ethernet/socionext/netsec.c | 97 ++++++++++++++-----------
1 file changed, 54 insertions(+), 43 deletions(-)
diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
index 584a6b3f6542..05a0948ad929 100644
--- a/drivers/net/ethernet/socionext/netsec.c
+++ b/drivers/net/ethernet/socionext/netsec.c
@@ -257,7 +257,6 @@ struct netsec_desc_ring {
dma_addr_t desc_dma;
struct netsec_desc *desc;
void *vaddr;
- u16 pkt_cnt;
u16 head, tail;
};
@@ -598,33 +597,26 @@ static void netsec_set_rx_de(struct netsec_priv *priv,
dring->desc[idx].len = desc->len;
}
-static int netsec_clean_tx_dring(struct netsec_priv *priv, int budget)
+static bool netsec_clean_tx_dring(struct netsec_priv *priv)
{
struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_TX];
unsigned int pkts, bytes;
-
- dring->pkt_cnt += netsec_read(priv, NETSEC_REG_NRM_TX_DONE_PKTCNT);
-
- if (dring->pkt_cnt < budget)
- budget = dring->pkt_cnt;
+ struct netsec_de *entry;
+ int tail = dring->tail;
+ int cnt = 0;
pkts = 0;
bytes = 0;
+ entry = dring->vaddr + DESC_SZ * tail;
- while (pkts < budget) {
+ while (!(entry->attr & (1U << NETSEC_TX_SHIFT_OWN_FIELD)) &&
+ cnt < DESC_NUM) {
struct netsec_desc *desc;
- struct netsec_de *entry;
- int tail, eop;
-
- tail = dring->tail;
-
- /* move tail ahead */
- dring->tail = (tail + 1) % DESC_NUM;
+ int eop;
desc = &dring->desc[tail];
- entry = dring->vaddr + DESC_SZ * tail;
-
eop = (entry->attr >> NETSEC_TX_LAST) & 1;
+ dma_rmb();
dma_unmap_single(priv->dev, desc->dma_addr, desc->len,
DMA_TO_DEVICE);
@@ -633,38 +625,51 @@ static int netsec_clean_tx_dring(struct netsec_priv *priv, int budget)
bytes += desc->skb->len;
dev_kfree_skb(desc->skb);
}
+ /* clean up so netsec_uninit_pkt_dring() won't free the skb
+ * again
+ */
*desc = (struct netsec_desc){};
+
+ /* entry->attr is not going to be accessed by the NIC until
+ * netsec_set_tx_de() is called. No need for a dma_wmb() here
+ */
+ entry->attr = 1U << NETSEC_TX_SHIFT_OWN_FIELD;
+ /* move tail ahead */
+ dring->tail = (tail + 1) % DESC_NUM;
+
+ tail = dring->tail;
+ entry = dring->vaddr + DESC_SZ * tail;
+ cnt++;
}
- dring->pkt_cnt -= budget;
- priv->ndev->stats.tx_packets += budget;
+ if (!cnt)
+ return false;
+
+ /* reading the register clears the irq */
+ netsec_read(priv, NETSEC_REG_NRM_TX_DONE_PKTCNT);
+
+ priv->ndev->stats.tx_packets += cnt;
priv->ndev->stats.tx_bytes += bytes;
- netdev_completed_queue(priv->ndev, budget, bytes);
+ netdev_completed_queue(priv->ndev, cnt, bytes);
- return budget;
+ return true;
}
-static int netsec_process_tx(struct netsec_priv *priv, int budget)
+static void netsec_process_tx(struct netsec_priv *priv)
{
struct net_device *ndev = priv->ndev;
- int new, done = 0;
+ bool cleaned;
- do {
- new = netsec_clean_tx_dring(priv, budget);
- done += new;
- budget -= new;
- } while (new);
+ cleaned = netsec_clean_tx_dring(priv);
- if (done && netif_queue_stopped(ndev)) {
+ if (cleaned && netif_queue_stopped(ndev)) {
/* Make sure we update the value, anyone stopping the queue
* after this will read the proper consumer idx
*/
smp_wmb();
netif_wake_queue(ndev);
}
-
- return done;
}
static void *netsec_alloc_rx_data(struct netsec_priv *priv,
@@ -813,24 +818,17 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
static int netsec_napi_poll(struct napi_struct *napi, int budget)
{
struct netsec_priv *priv;
- int tx, rx, done, todo;
+ int rx, done, todo;
priv = container_of(napi, struct netsec_priv, napi);
+ netsec_process_tx(priv);
+
todo = budget;
do {
- if (!todo)
- break;
-
- tx = netsec_process_tx(priv, todo);
- todo -= tx;
-
- if (!todo)
- break;
-
rx = netsec_process_rx(priv, todo);
todo -= rx;
- } while (rx || tx);
+ } while (rx);
done = budget - todo;
@@ -1007,7 +1005,6 @@ static void netsec_uninit_pkt_dring(struct netsec_priv *priv, int id)
dring->head = 0;
dring->tail = 0;
- dring->pkt_cnt = 0;
if (id == NETSEC_RING_TX)
netdev_reset_queue(priv->ndev);
@@ -1030,6 +1027,7 @@ static void netsec_free_dring(struct netsec_priv *priv, int id)
static int netsec_alloc_dring(struct netsec_priv *priv, enum ring_id id)
{
struct netsec_desc_ring *dring = &priv->desc_ring[id];
+ int i;
dring->vaddr = dma_zalloc_coherent(priv->dev, DESC_SZ * DESC_NUM,
&dring->desc_dma, GFP_KERNEL);
@@ -1040,6 +1038,19 @@ static int netsec_alloc_dring(struct netsec_priv *priv, enum ring_id id)
if (!dring->desc)
goto err;
+ if (id == NETSEC_RING_TX) {
+ for (i = 0; i < DESC_NUM; i++) {
+ struct netsec_de *de;
+
+ de = dring->vaddr + (DESC_SZ * i);
+ /* de->attr is not going to be accessed by the NIC
+ * until netsec_set_tx_de() is called.
+ * No need for a dma_wmb() here
+ */
+ de->attr = 1U << NETSEC_TX_SHIFT_OWN_FIELD;
+ }
+ }
+
return 0;
err:
netsec_free_dring(priv, id);
--
2.19.1
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