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authorEric Dumazet <eric.dumazet@gmail.com>2009-06-05 06:04:16 +0200
committerDavid S. Miller <davem@davemloft.net>2009-06-08 09:21:48 +0200
commit042a53a9e437feaf2230dd2cadcecfae9c7bfe05 (patch)
treeae9078f61e390a3014aecb3fe80d3438ab25ee51 /net/core
parentnet: num_dma_maps is not used (diff)
downloadlinux-042a53a9e437feaf2230dd2cadcecfae9c7bfe05.tar.xz
linux-042a53a9e437feaf2230dd2cadcecfae9c7bfe05.zip
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>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/skb_dma_map.c12
1 files changed, 6 insertions, 6 deletions
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);
}
}