On 11/2/19 8:03 AM, Jens Axboe wrote: > On 11/2/19 1:29 AM, Ming Lei wrote: >> __blk_queue_split() may be a bit heavy for small block size(such as >> 512B, or 4KB) IO, so introduce one flag to decide if this bio includes >> multiple page. And only consider to try splitting this bio in case >> that the multiple page flag is set. >> >> ~3% - 5% IOPS improvement can be observed on io_uring test over >> null_blk(MQ), and the io_uring test code is from fio/t/io_uring.c >> >> bch_bio_map() should be the only one which doesn't use bio_add_page(), >> so force to mark bio built via bch_bio_map() as MULTI_PAGE. >> >> RAID5 has similar usage too, however the bio is really single-page bio, >> so not necessary to handle it. > > Thanks Ming, applied. Actually, I took a closer look at this. I thought the BIO_MAP_USER overload would be ok, but that seems potentially fragile and so does the fact that we need to now maintain an extra state for multipage. Any serious objections to just doing the somewhat hacky bio->bi_vcnt check? With a comment I think that's more acceptable, and it doesn't rely on maintaining extra state. Particularly the latter is a big win, imho. -- Jens Axboe
