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7dbc515f5c
Improve the performance of sys_fillrect() by using word-aligned 32/64-bit mov instructions. While the code tried to implement this, the compiler failed to create fast instructions. The resulting binary instructions were even slower than cfb_fillrect(), which uses the same algorithm, but operates on I/O memory. A microbenchmark measures the average number of CPU cycles for sys_fillrect() after a stabilizing period of a few minutes (i7-4790, FullHD, simpledrm, kernel with debugging). The value for CFB is given as a reference. sys_fillrect(), new: 26586 cycles sys_fillrect(), old: 166603 cycles cfb_fillrect(): 41012 cycles In the optimized case, sys_fillrect() is now ~6x faster than before and ~1.5x faster than the CFB implementation. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> Reviewed-by: Sam Ravnborg <sam@ravnborg.org> Link: https://patchwork.freedesktop.org/patch/msgid/20220223193804.18636-2-tzimmermann@suse.de
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.