86d231459d
A lot of the performance gain comes from this patch. While analysing performance overhead it was found that the largest CPU stalls were caused when touching the struct page area. It is first read with a READ_ONCE from build_skb_around via page_is_pfmemalloc(), and when freed written by page_frag_free() call. Measurements show that the prefetchw (W) variant operation is needed to achieve the performance gain. We believe this optimization it two fold, first the W-variant saves one step in the cache-coherency protocol, and second it helps us to avoid the non-temporal prefetch HW optimizations and bring this into all cache-levels. It might be worth investigating if prefetch into L2 will have the same benefit. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org> Acked-by: Song Liu <songliubraving@fb.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.
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.