net: skb_shared_info optimization
skb_dma_unmap() is quite expensive for small packets,
because we use two different cache lines from skb_shared_info.
One to access nr_frags, one to access dma_maps[0]
Instead of dma_maps being an array of MAX_SKB_FRAGS + 1 elements,
let dma_head alone in a new dma_head field, close to nr_frags,
to reduce cache lines misses.
Tested on my dev machine (bnx2 & tg3 adapters), nice speedup !
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/bnx2.c b/drivers/net/bnx2.c
index f530172..391d2d4 100644
--- a/drivers/net/bnx2.c
+++ b/drivers/net/bnx2.c
@@ -5487,7 +5487,7 @@
dev_kfree_skb(skb);
return -EIO;
}
- map = skb_shinfo(skb)->dma_maps[0];
+ map = skb_shinfo(skb)->dma_head;
REG_WR(bp, BNX2_HC_COMMAND,
bp->hc_cmd | BNX2_HC_COMMAND_COAL_NOW_WO_INT);
@@ -6167,7 +6167,7 @@
}
sp = skb_shinfo(skb);
- mapping = sp->dma_maps[0];
+ mapping = sp->dma_head;
tx_buf = &txr->tx_buf_ring[ring_prod];
tx_buf->skb = skb;
@@ -6191,7 +6191,7 @@
txbd = &txr->tx_desc_ring[ring_prod];
len = frag->size;
- mapping = sp->dma_maps[i + 1];
+ mapping = sp->dma_maps[i];
txbd->tx_bd_haddr_hi = (u64) mapping >> 32;
txbd->tx_bd_haddr_lo = (u64) mapping & 0xffffffff;