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The compiler does an efficient job of inlining static C functions. Perf top clearly shows that almost everything gets inlined into the function call xdp_do_redirect. The function xdp_do_redirect end-up containing and interleaving the map and non-map redirect code. This is sub-optimal, as it would be strange for an XDP program to use both types of redirect in the same program. The two use-cases are separate, and interleaving the code just cause more instruction-cache pressure. I would like to stress (again) that the non-map variant bpf_redirect is very slow compared to the bpf_redirect_map variant, approx half the speed. Measured with driver i40e the difference is: - map redirect: 13,250,350 pps - non-map redirect: 7,491,425 pps For this reason, the function name of the non-map variant of redirect have been called xdp_do_redirect_slow. This hopefully gives a hint when using perf, that this is not the optimal XDP redirect operating mode. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Alexei Starovoitov <ast@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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.