From a418950c1378c4a3722baecdbe98df78ea23f231 Mon Sep 17 00:00:00 2001 From: Lennert Buytenhek Date: Sat, 13 Sep 2008 04:16:15 +0200 Subject: [PATCH] mv643xx_eth: avoid dropping tx lock during transmit reclaim By moving DMA unmapping during transmit reclaim back under the netif tx lock, we avoid the situation where we read the DMA address and buffer length from the descriptor under the lock and then not do anything with that data after dropping the lock on platforms where the DMA unmapping routines are all NOPs (which is the case on all ARM platforms that mv643xx_eth is used on at least). This saves two uncached reads, which makes a small but measurable performance difference in routing benchmarks. Signed-off-by: Lennert Buytenhek --- drivers/net/mv643xx_eth.c | 22 +++++++--------------- 1 file changed, 7 insertions(+), 15 deletions(-) diff --git a/drivers/net/mv643xx_eth.c b/drivers/net/mv643xx_eth.c index d653b5a19e7..7410eca8782 100644 --- a/drivers/net/mv643xx_eth.c +++ b/drivers/net/mv643xx_eth.c @@ -866,8 +866,6 @@ static int txq_reclaim(struct tx_queue *txq, int budget, int force) struct tx_desc *desc; u32 cmd_sts; struct sk_buff *skb; - dma_addr_t addr; - int count; tx_index = txq->tx_used_desc; desc = &txq->tx_desc_area[tx_index]; @@ -886,8 +884,6 @@ static int txq_reclaim(struct tx_queue *txq, int budget, int force) reclaimed++; txq->tx_desc_count--; - addr = desc->buf_ptr; - count = desc->byte_cnt; skb = txq->tx_skb[tx_index]; txq->tx_skb[tx_index] = NULL; @@ -896,20 +892,16 @@ static int txq_reclaim(struct tx_queue *txq, int budget, int force) mp->dev->stats.tx_errors++; } - /* - * Drop tx queue lock while we free the skb. - */ - __netif_tx_unlock(nq); - - if (cmd_sts & TX_FIRST_DESC) - dma_unmap_single(NULL, addr, count, DMA_TO_DEVICE); - else - dma_unmap_page(NULL, addr, count, DMA_TO_DEVICE); + if (cmd_sts & TX_FIRST_DESC) { + dma_unmap_single(NULL, desc->buf_ptr, + desc->byte_cnt, DMA_TO_DEVICE); + } else { + dma_unmap_page(NULL, desc->buf_ptr, + desc->byte_cnt, DMA_TO_DEVICE); + } if (skb) dev_kfree_skb(skb); - - __netif_tx_lock(nq, smp_processor_id()); } __netif_tx_unlock(nq); -- 2.20.1