[PATCH] [7/11] pasemi_mac: further performance tweaks
Olof Johansson
olof at lixom.net
Wed Oct 3 07:27:15 EST 2007
pasemi_mac: further performance tweaks
Misc driver tweaks for pasemi_mac:
* Increase ring size (really needed mostly on 10G)
* Take out an unneeded barrier
* Move around a few prefetches and reorder a few calls
* Don't try to clean on full tx buffer, just let things
take their course and stop the queue directly
* Avoid filling on the same line as the interface is
working on to reduce cache line bouncing
* Avoid unneeded clearing of software state (and make the
interface shutdown code handle it)
* Fix up some of the tx ring wrap logic.
Signed-off-by: Olof Johansson <olof at lixom.net>
Index: k.org/drivers/net/pasemi_mac.c
===================================================================
--- k.org.orig/drivers/net/pasemi_mac.c
+++ k.org/drivers/net/pasemi_mac.c
@@ -56,8 +56,8 @@
/* Must be a power of two */
-#define RX_RING_SIZE 512
-#define TX_RING_SIZE 512
+#define RX_RING_SIZE 4096
+#define TX_RING_SIZE 4096
#define DEFAULT_MSG_ENABLE \
(NETIF_MSG_DRV | \
@@ -336,8 +336,16 @@ static void pasemi_mac_free_tx_resources
struct pasemi_mac_buffer *info;
dma_addr_t dmas[MAX_SKB_FRAGS+1];
int freed;
+ int start, limit;
- for (i = 0; i < TX_RING_SIZE; i += freed) {
+ start = mac->tx->next_to_clean;
+ limit = mac->tx->next_to_fill;
+
+ /* Compensate for when fill has wrapped and clean has not */
+ if (start > limit)
+ limit += TX_RING_SIZE;
+
+ for (i = start; i < limit; i += freed) {
info = &TX_RING_INFO(mac, i+1);
if (info->dma && info->skb) {
for (j = 0; j <= skb_shinfo(info->skb)->nr_frags; j++)
@@ -520,9 +528,6 @@ static int pasemi_mac_clean_rx(struct pa
n = mac->rx->next_to_clean;
for (count = limit; count; count--) {
-
- rmb();
-
macrx = RX_RING(mac, n);
if ((macrx & XCT_MACRX_E) ||
@@ -550,14 +555,10 @@ static int pasemi_mac_clean_rx(struct pa
break;
}
- prefetchw(info);
-
skb = info->skb;
- prefetchw(skb);
- info->dma = 0;
- pci_unmap_single(mac->dma_pdev, dma, skb->len,
- PCI_DMA_FROMDEVICE);
+ prefetch(skb);
+ prefetch(&skb->data_len);
len = (macrx & XCT_MACRX_LLEN_M) >> XCT_MACRX_LLEN_S;
@@ -576,10 +577,9 @@ static int pasemi_mac_clean_rx(struct pa
} else
info->skb = NULL;
- /* Need to zero it out since hardware doesn't, since the
- * replenish loop uses it to tell when it's done.
- */
- RX_BUFF(mac, i) = 0;
+ pci_unmap_single(mac->dma_pdev, dma, len, PCI_DMA_FROMDEVICE);
+
+ info->dma = 0;
skb_put(skb, len);
@@ -599,6 +599,11 @@ static int pasemi_mac_clean_rx(struct pa
RX_RING(mac, n) = 0;
RX_RING(mac, n+1) = 0;
+ /* Need to zero it out since hardware doesn't, since the
+ * replenish loop uses it to tell when it's done.
+ */
+ RX_BUFF(mac, i) = 0;
+
n += 2;
}
@@ -621,27 +626,33 @@ static int pasemi_mac_clean_rx(struct pa
static int pasemi_mac_clean_tx(struct pasemi_mac *mac)
{
int i, j;
- struct pasemi_mac_buffer *info;
- unsigned int start, descr_count, buf_count, limit;
+ unsigned int start, descr_count, buf_count, batch_limit;
+ unsigned int ring_limit;
unsigned int total_count;
unsigned long flags;
struct sk_buff *skbs[TX_CLEAN_BATCHSIZE];
dma_addr_t dmas[TX_CLEAN_BATCHSIZE][MAX_SKB_FRAGS+1];
total_count = 0;
- limit = TX_CLEAN_BATCHSIZE;
+ batch_limit = TX_CLEAN_BATCHSIZE;
restart:
spin_lock_irqsave(&mac->tx->lock, flags);
start = mac->tx->next_to_clean;
+ ring_limit = mac->tx->next_to_fill;
+
+ /* Compensate for when fill has wrapped but clean has not */
+ if (start > ring_limit)
+ ring_limit += TX_RING_SIZE;
buf_count = 0;
descr_count = 0;
for (i = start;
- descr_count < limit && i < mac->tx->next_to_fill;
+ descr_count < batch_limit && i < ring_limit;
i += buf_count) {
u64 mactx = TX_RING(mac, i);
+ struct sk_buff *skb;
if ((mactx & XCT_MACTX_E) ||
(*mac->tx_status & PAS_STATUS_ERROR))
@@ -651,19 +662,15 @@ restart:
/* Not yet transmitted */
break;
- info = &TX_RING_INFO(mac, i+1);
- skbs[descr_count] = info->skb;
+ skb = TX_RING_INFO(mac, i+1).skb;
+ skbs[descr_count] = skb;
- buf_count = 2 + skb_shinfo(info->skb)->nr_frags;
- for (j = 0; j <= skb_shinfo(info->skb)->nr_frags; j++)
+ buf_count = 2 + skb_shinfo(skb)->nr_frags;
+ for (j = 0; j <= skb_shinfo(skb)->nr_frags; j++)
dmas[descr_count][j] = TX_RING_INFO(mac, i+1+j).dma;
-
- info->dma = 0;
TX_RING(mac, i) = 0;
TX_RING(mac, i+1) = 0;
- TX_RING_INFO(mac, i+1).skb = 0;
- TX_RING_INFO(mac, i+1).dma = 0;
/* Since we always fill with an even number of entries, make
* sure we skip any unused one at the end as well.
@@ -672,7 +679,7 @@ restart:
buf_count++;
descr_count++;
}
- mac->tx->next_to_clean = i;
+ mac->tx->next_to_clean = i & (TX_RING_SIZE-1);
spin_unlock_irqrestore(&mac->tx->lock, flags);
netif_wake_queue(mac->netdev);
@@ -683,7 +690,7 @@ restart:
total_count += descr_count;
/* If the batch was full, try to clean more */
- if (descr_count == limit)
+ if (descr_count == batch_limit)
goto restart;
return total_count;
@@ -1106,19 +1113,14 @@ static int pasemi_mac_start_tx(struct sk
spin_lock_irqsave(&txring->lock, flags);
- if (RING_AVAIL(txring) <= nfrags+3) {
- spin_unlock_irqrestore(&txring->lock, flags);
- pasemi_mac_clean_tx(mac);
- pasemi_mac_restart_tx_intr(mac);
- spin_lock_irqsave(&txring->lock, flags);
-
- if (RING_AVAIL(txring) <= nfrags+3) {
- /* Still no room -- stop the queue and wait for tx
- * intr when there's room.
- */
- netif_stop_queue(dev);
- goto out_err;
- }
+ /* Avoid stepping on the same cache line that the DMA controller
+ * is currently about to send, so leave at least 8 words available.
+ * Total free space needed is mactx + fragments + 8
+ */
+ if (RING_AVAIL(txring) < nfrags + 10) {
+ /* no room -- stop the queue and wait for tx intr */
+ netif_stop_queue(dev);
+ goto out_err;
}
TX_RING(mac, txring->next_to_fill) = mactx;
@@ -1137,8 +1139,8 @@ static int pasemi_mac_start_tx(struct sk
if (nfrags & 1)
nfrags++;
- txring->next_to_fill += nfrags + 1;
-
+ txring->next_to_fill = (txring->next_to_fill + nfrags + 1) &
+ (TX_RING_SIZE-1);
dev->stats.tx_packets++;
dev->stats.tx_bytes += skb->len;
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