From 042a53a9e437feaf2230dd2cadcecfae9c7bfe05 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 5 Jun 2009 04:04:16 +0000 Subject: 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 Signed-off-by: David S. Miller --- net/core/skb_dma_map.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'net/core') diff --git a/net/core/skb_dma_map.c b/net/core/skb_dma_map.c index 7adb623ef664..79687dfd6957 100644 --- a/net/core/skb_dma_map.c +++ b/net/core/skb_dma_map.c @@ -20,7 +20,7 @@ int skb_dma_map(struct device *dev, struct sk_buff *skb, if (dma_mapping_error(dev, map)) goto out_err; - sp->dma_maps[0] = map; + sp->dma_head = map; for (i = 0; i < sp->nr_frags; i++) { skb_frag_t *fp = &sp->frags[i]; @@ -28,7 +28,7 @@ int skb_dma_map(struct device *dev, struct sk_buff *skb, fp->size, dir); if (dma_mapping_error(dev, map)) goto unwind; - sp->dma_maps[i + 1] = map; + sp->dma_maps[i] = map; } return 0; @@ -37,10 +37,10 @@ unwind: while (--i >= 0) { skb_frag_t *fp = &sp->frags[i]; - dma_unmap_page(dev, sp->dma_maps[i + 1], + dma_unmap_page(dev, sp->dma_maps[i], fp->size, dir); } - dma_unmap_single(dev, sp->dma_maps[0], + dma_unmap_single(dev, sp->dma_head, skb_headlen(skb), dir); out_err: return -ENOMEM; @@ -53,12 +53,12 @@ void skb_dma_unmap(struct device *dev, struct sk_buff *skb, struct skb_shared_info *sp = skb_shinfo(skb); int i; - dma_unmap_single(dev, sp->dma_maps[0], + dma_unmap_single(dev, sp->dma_head, skb_headlen(skb), dir); for (i = 0; i < sp->nr_frags; i++) { skb_frag_t *fp = &sp->frags[i]; - dma_unmap_page(dev, sp->dma_maps[i + 1], + dma_unmap_page(dev, sp->dma_maps[i], fp->size, dir); } } -- cgit v1.2.3