Commit f4ae8420 authored by Christoph Paasch's avatar Christoph Paasch Committed by Jakub Kicinski
Browse files

mpls: Reduce skb re-allocations due to skb_cow() 



mpls_xmit() needs to prepend the MPLS-labels to the packet. That implies
one needs to make sure there is enough space for it in the headers.

Calling skb_cow() implies however that one wants to change even the
playload part of the packet (which is not true for MPLS). Thus, call
skb_cow_head() instead, which is what other tunnelling protocols do.

Running a server with this comm it entirely removed the calls to
pskb_expand_head() from the callstack in mpls_xmit() thus having
significant CPU-reduction, especially at peak times.

Cc: Roopa Prabhu <roopa@nvidia.com>
Reported-by: default avatarCraig Taylor <cmtaylor@apple.com>
Signed-off-by: default avatarChristoph Paasch <cpaasch@apple.com>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240815161201.22021-1-cpaasch@apple.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 1c66df86

net/mpls/mpls_iptunnel.c

+1 −1
Original line number Diff line number Diff line
@@ -106,7 +106,7 @@ static int mpls_xmit(struct sk_buff *skb) 
		hh_len = 0;



	/* Ensure there is enough space for the headers in the skb */

	if (skb_cow(skb, hh_len + new_header_size))

	if (skb_cow_head(skb, hh_len + new_header_size))

		goto drop;



	skb_set_inner_protocol(skb, skb->protocol);