From 7e5d7753956b374516530e156c5e8aa19652398d Mon Sep 17 00:00:00 2001 From: Malcolm Crossley Date: Wed, 5 Nov 2014 10:50:22 +0000 Subject: [PATCH] xen-netback: remove unconditional __pskb_pull_tail() in guest Tx path Unconditionally pulling 128 bytes into the linear area is not required for: - security: Every protocol demux starts with pskb_may_pull() to pull frag data into the linear area, if necessary, before looking at headers. - performance: Netback has already grant copied up-to 128 bytes from the first slot of a packet into the linear area. The first slot normally contain all the IPv4/IPv6 and TCP/UDP headers. The unconditional pull would often copy frag data unnecessarily. This is a performance problem when running on a version of Xen where grant unmap avoids TLB flushes for pages which are not accessed. TLB flushes can now be avoided for > 99% of unmaps (it was 0% before). Grant unmap TLB flush avoidance will be available in a future version of Xen (probably 4.6). Signed-off-by: Malcolm Crossley Signed-off-by: David Vrabel Acked-by: Ian Campbell Signed-off-by: David S. Miller --- Reading git-format-patch failed