On 11/9/18 9:53 AM, jianchao.wang wrote: > Hi Jens > > On 11/9/18 12:06 AM, Jens Axboe wrote: >> DM currently uses atomic inc/dec to maintain a busy count of >> IO on a given device. For the dm-mq path, we can replace this >> with helper that just checks the state of the tags on the device. >> >> First patch is a prep patch that allows the iteration helpers >> to return true/false, like we support internally in sbitmap. >> For a busy check we don't care about how many requests are >> busy, just if some are or not. Hence we can stop iterating >> tags as soon as we find one that is allocated. > > If we don't care about how many requests are busy, why not check > sb->map[idex].word directly ? It could be more efficient. > Oh, we need to check rq->q for the tag shared case. > Thanks > Jianchao >
