mirror of https://gitee.com/openkylin/linux.git
ipv6: sr: expand skb head only if necessary
To insert or encapsulate a packet with an SRH, we need a large enough skb headroom. Currently, we are using pskb_expand_head to inconditionally increase the size of the headroom by the amount needed by the SRH (and IPv6 header). If this reallocation is performed by another CPU than the one that initially allocated the skb, then when the initial CPU kfree the skb, it will enter the __slab_free slowpath, impacting performances. This patch replaces pskb_expand_head with skb_cow_head, that will reallocate the skb head only if the headroom is not large enough. Performances for SRH encapsulation before the patch: Result: OK: 7348320(c7347271+d1048) usec, 5000000 (1000byte,0frags) 680427pps 5443Mb/sec (5443416000bps) errors: 0 Performances after the patch: Result: OK: 5656067(c5655678+d388) usec, 5000000 (1000byte,0frags) 884006pps 7072Mb/sec (7072048000bps) errors: 0 Signed-off-by: David Lebrun <david.lebrun@uclouvain.be> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -105,7 +105,7 @@ static int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
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hdrlen = (osrh->hdrlen + 1) << 3;
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tot_len = hdrlen + sizeof(*hdr);
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err = pskb_expand_head(skb, tot_len, 0, GFP_ATOMIC);
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err = skb_cow_head(skb, tot_len);
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if (unlikely(err))
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return err;
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@ -156,7 +156,7 @@ static int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
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hdrlen = (osrh->hdrlen + 1) << 3;
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err = pskb_expand_head(skb, hdrlen, 0, GFP_ATOMIC);
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err = skb_cow_head(skb, hdrlen);
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if (unlikely(err))
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return err;
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