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mv643xx_eth: rework receive skb cache alignment 

On the platforms that mv643xx_eth is used on, the manual skb->data
alignment logic in mv643xx_eth can be simplified, as the only case we
need to handle is where NET_SKB_PAD is not a multiple of the cache
line size.  If this is the case, the extra padding we need can be
computed at compile time, while if NET_SKB_PAD _is_ a multiple of
the cache line size, the code can be optimised out entirely.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Lennert Buytenhek 2009-05-06 03:01:22 +00:00 committed by David S. Miller
parent becfad979d
commit 7fd96ce47f
1 changed files with 13 additions and 8 deletions
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21
drivers/net/mv643xx_eth.c
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@ -174,6 +174,7 @@ static char mv643xx_eth_driver_version[] = "1.4";
*/ */
#define DEFAULT_RX_QUEUE_SIZE 128 #define DEFAULT_RX_QUEUE_SIZE 128
#define DEFAULT_TX_QUEUE_SIZE 256 #define DEFAULT_TX_QUEUE_SIZE 256
#define SKB_DMA_REALIGN ((PAGE_SIZE - NET_SKB_PAD) % SMP_CACHE_BYTES)
/* /*
@ -649,23 +650,20 @@ static int rxq_refill(struct rx_queue *rxq, int budget)
refilled = 0; refilled = 0;
while (refilled < budget && rxq->rx_desc_count < rxq->rx_ring_size) { while (refilled < budget && rxq->rx_desc_count < rxq->rx_ring_size) {
struct sk_buff *skb; struct sk_buff *skb;
int unaligned;
int rx; int rx;
struct rx_desc *rx_desc; struct rx_desc *rx_desc;
skb = __skb_dequeue(&mp->rx_recycle); skb = __skb_dequeue(&mp->rx_recycle);
if (skb == NULL) if (skb == NULL)
skb = dev_alloc_skb(mp->skb_size + skb = dev_alloc_skb(mp->skb_size);
dma_get_cache_alignment() - 1);
if (skb == NULL) { if (skb == NULL) {
mp->oom = 1; mp->oom = 1;
goto oom; goto oom;
} }
unaligned = (u32)skb->data & (dma_get_cache_alignment() - 1); if (SKB_DMA_REALIGN)
if (unaligned) skb_reserve(skb, SKB_DMA_REALIGN);
skb_reserve(skb, dma_get_cache_alignment() - unaligned);
refilled++; refilled++;
rxq->rx_desc_count++; rxq->rx_desc_count++;
@ -964,8 +962,7 @@ static int txq_reclaim(struct tx_queue *txq, int budget, int force)
if (skb != NULL) { if (skb != NULL) {
if (skb_queue_len(&mp->rx_recycle) < if (skb_queue_len(&mp->rx_recycle) <
mp->rx_ring_size && mp->rx_ring_size &&
skb_recycle_check(skb, mp->skb_size + skb_recycle_check(skb, mp->skb_size))
dma_get_cache_alignment() - 1))
__skb_queue_head(&mp->rx_recycle, skb); __skb_queue_head(&mp->rx_recycle, skb);
else else
dev_kfree_skb(skb); dev_kfree_skb(skb);
@ -2336,6 +2333,14 @@ static void mv643xx_eth_recalc_skb_size(struct mv643xx_eth_private *mp)
* size field are ignored by the hardware. * size field are ignored by the hardware.
*/ */
mp->skb_size = (skb_size + 7) & ~7; mp->skb_size = (skb_size + 7) & ~7;
/*
* If NET_SKB_PAD is smaller than a cache line,
* netdev_alloc_skb() will cause skb->data to be misaligned
* to a cache line boundary. If this is the case, include
* some extra space to allow re-aligning the data area.
*/
mp->skb_size += SKB_DMA_REALIGN;
} }
static int mv643xx_eth_open(struct net_device *dev) static int mv643xx_eth_open(struct net_device *dev)