On Sun, Jan 09, 2022 at 06:54:21PM -0700, Jens Axboe wrote: > On 1/9/22 6:50 PM, Ming Lei wrote: > > Only the last sbitmap_word can have different depth, and all the others > > must have same depth of 1U << sb->shift, so not necessary to store it in > > sbitmap_word, and it can be retrieved easily and efficiently by adding > > one internal helper of __map_depth(sb, index). > > > > Not see performance effect when running iops test on null_blk. > > > > This way saves us one cacheline(usually 64 words) per each sbitmap_word. > > We probably want to kill the ____cacheline_aligned_in_smp from 'word' as > well. But sbitmap_deferred_clear_bit() is called in put fast path, then the cacheline becomes shared with get path, and I guess this way isn't expected. Thanks, Ming
