On Mon, Feb 15, 2021 at 01:30:44PM -0800, Yury Norov wrote: > [add David Laight <David.Laight@xxxxxxxxxx> ] > > On Sat, Jan 30, 2021 at 11:17:11AM -0800, Yury Norov wrote: > > Bitmap operations are much simpler and faster in case of small bitmaps > > which fit into a single word. In linux/bitmap.h we have a machinery that > > allows compiler to replace actual function call with a few instructions > > if bitmaps passed into the function are small and their size is known at > > compile time. > > > > find_*_bit() API lacks this functionality; despite users will benefit from > > it a lot. One important example is cpumask subsystem when > > NR_CPUS <= BITS_PER_LONG. In the very best case, the compiler may replace > > a find_*_bit() call for such a bitmap with a single ffs or ffz instruction. > > > > Tools is synchronized with new implementation where needed. > > > > v1: https://www.spinics.net/lists/kernel/msg3804727.html > > v2: - employ GENMASK() for bitmaps; > > - unify find_bit inliners in; > > - address comments to v1; > > Comments so far: > - increased image size (patch #8) - addressed by introducing > CONFIG_FAST_PATH; > - split tools and kernel parts - not clear why it's better. Because tools are user space programs and sometimes may not follow kernel specifics, so they are different logically and changes should be separated. > Anything else? -- With Best Regards, Andy Shevchenko
