On 2/2/21 7:36 PM, Lin Feng wrote: > Hi all, > > On 2/2/21 22:20, Jens Axboe wrote: >> On 2/2/21 5:28 AM, Jan Kara wrote: >>> Hello! >>> >>> On Fri 29-01-21 19:18:08, Lin Feng wrote: >>>> This reverts commit 6d4d273588378c65915acaf7b2ee74e9dd9c130a. >>>> >>>> bfq.limit_depth passes word_depths[] as shallow_depth down to sbitmap core >>>> sbitmap_get_shallow, which uses just the number to limit the scan depth of >>>> each bitmap word, formula: >>>> scan_percentage_for_each_word = shallow_depth / (1 << sbimap->shift) * 100% >>> >>> Looking at sbitmap_get_shallow() again more carefully, I agree that I >>> misunderstood how shallow_depth argument gets used and the original code >>> was correct and I broke it. Thanks for spotting this! >>> >>> What I didn't notice is that shallow_depth indeed gets used for each bitmap >>> word separately and not for bitmap as a whole. I'd say this could use some >>> more documentation but that's unrelated to your revert. So feel free to add: >>> >>> Reviewed-by: Jan Kara <jack@xxxxxxx> >> >> I don't have the original patch (neither directly nor in the archive), so >> I had to hand-apply it. In any case, applied for 5.11, thanks. >> > > Take a look at linux-block.git tree, the hand-applied commit for this patch > is broken, the following changing line is left out: > - bfqd->word_depths[0][1] = max((bt->sb.depth * 3) >> 2, 1U); > + bfqd->word_depths[0][1] = max(((1U << bt->sb.shift) * 3) >> 2, 1U); > > Sorry for making troubles to you, I will resend this patch with tiny commit > log typo fix(sbimap -> sbitmap) and attaching Jan's Reviewed-by, also thanks > his time for reviewing. > > Hope this time lkml server will not block my patch. Thanks for checking - just send me an incremental and I'll fold it in. -- Jens Axboe
