From 19d5a26f5ef8de5dcb78799feaf404d717b1aac3 Mon Sep 17 00:00:00 2001 From: David Lebrun Date: Fri, 24 Mar 2017 10:46:26 +0100 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- net/ipv6/seg6_iptunnel.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c index 85582257d3af..dda2c5147ef0 100644 --- a/net/ipv6/seg6_iptunnel.c +++ b/net/ipv6/seg6_iptunnel.c @@ -105,7 +105,7 @@ static int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh) hdrlen = (osrh->hdrlen + 1) << 3; tot_len = hdrlen + sizeof(*hdr); - err = pskb_expand_head(skb, tot_len, 0, GFP_ATOMIC); + err = skb_cow_head(skb, tot_len); if (unlikely(err)) return err; @@ -156,7 +156,7 @@ static int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh) hdrlen = (osrh->hdrlen + 1) << 3; - err = pskb_expand_head(skb, hdrlen, 0, GFP_ATOMIC); + err = skb_cow_head(skb, hdrlen); if (unlikely(err)) return err; -- 2.30.2