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It was observed that sending data via batadv over vxlan (on top of wireguard) reduced the performance massively compared to raw ethernet or batadv on raw ethernet. A check of perf data showed that the vxlan_build_skb was calling all the time pskb_expand_head to allocate enough headroom for: min_headroom = LL_RESERVED_SPACE(dst->dev) + dst->header_len + VXLAN_HLEN + iphdr_len; But the vxlan_config_apply only requested needed headroom for: lowerdev->hard_header_len + VXLAN6_HEADROOM or VXLAN_HEADROOM So it completely ignored the needed_headroom of the lower device. The first caller of net_dev_xmit could therefore never make sure that enough headroom was allocated for the rest of the transmit path. Cc: Annika Wickert <annika.wickert@exaring.de> Signed-off-by: Sven Eckelmann <sven@narfation.org> Tested-by: Annika Wickert <aw@awlnx.space> Link: https://lore.kernel.org/r/20201126125247.1047977-1-sven@narfation.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.