042a53a9e4
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>
66 lines
1.4 KiB
C
66 lines
1.4 KiB
C
/* skb_dma_map.c: DMA mapping helpers for socket buffers.
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*
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* Copyright (C) David S. Miller <davem@davemloft.net>
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/dma-mapping.h>
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#include <linux/skbuff.h>
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int skb_dma_map(struct device *dev, struct sk_buff *skb,
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enum dma_data_direction dir)
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{
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struct skb_shared_info *sp = skb_shinfo(skb);
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dma_addr_t map;
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int i;
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map = dma_map_single(dev, skb->data,
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skb_headlen(skb), dir);
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if (dma_mapping_error(dev, map))
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goto out_err;
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sp->dma_head = map;
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for (i = 0; i < sp->nr_frags; i++) {
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skb_frag_t *fp = &sp->frags[i];
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map = dma_map_page(dev, fp->page, fp->page_offset,
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fp->size, dir);
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if (dma_mapping_error(dev, map))
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goto unwind;
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sp->dma_maps[i] = map;
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}
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return 0;
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unwind:
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while (--i >= 0) {
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skb_frag_t *fp = &sp->frags[i];
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dma_unmap_page(dev, sp->dma_maps[i],
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fp->size, dir);
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}
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dma_unmap_single(dev, sp->dma_head,
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skb_headlen(skb), dir);
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out_err:
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return -ENOMEM;
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}
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EXPORT_SYMBOL(skb_dma_map);
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void skb_dma_unmap(struct device *dev, struct sk_buff *skb,
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enum dma_data_direction dir)
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{
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struct skb_shared_info *sp = skb_shinfo(skb);
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int i;
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dma_unmap_single(dev, sp->dma_head,
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skb_headlen(skb), dir);
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for (i = 0; i < sp->nr_frags; i++) {
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skb_frag_t *fp = &sp->frags[i];
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dma_unmap_page(dev, sp->dma_maps[i],
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fp->size, dir);
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}
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}
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EXPORT_SYMBOL(skb_dma_unmap);
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