mirror of https://gitee.com/openkylin/linux.git
f5d45dc911
The generic memcpy routine provided in kernel does only byte copies. Using word copies we can lower boot time and cycles spend in memcpy quite significantly. Booting on my de0 nano I see boot times go from 7.2 to 5.6 seconds. The avg cycles in memcpy during boot go from 6467 to 1887. I tested several algorithms (see code in previous patch mails) The implementations I tested and avg cycles: - Word Copies + Loop Unrolls + Non Aligned 1882 - Word Copies + Loop Unrolls 1887 - Word Copies 2441 - Byte Copies + Loop Unrolls 6467 - Byte Copies 7600 In the end I ended up going with Word Copies + Loop Unrolls as it provides best tradeoff between simplicity and boot speedups. Signed-off-by: Stafford Horne <shorne@gmail.com> |
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| kernel | ||
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| README | ||
README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.