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John Stultz provided the outline for this patch back in May 2014 here: http://patches.linaro.org/patch/30501/ but I let this sit on the shelf for too long and in the intervening years almost every field in "struct timekeeper" was changed. So this is almost completely different from his original. Though the key change in arch/ia64/kernel/fsys.S remains the same. The core logic change with the updated vsyscall method is that we preserve the base nanosecond value in shifted nanoseconds, which allows us to avoid truncating and rounding up to the next nanosecond every tick to avoid inconsistencies. Thus the logic moved from nsec = ((cycle_delta * mult)>>shift) + base_nsec; to nsec = ((cycle_delta * mult) + base_snsec) >> shift; Cc: John Stultz <john.stultz@linaro.org> Cc: linux-ia64@vger.kernel.org Signed-off-by: Tony Luck <tony.luck@intel.com>
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.