Re: [External] Re: [PATCH] blk-throtl: Introduce sync and async queues for blk-throtl

[hanjinke]

在 2022/12/20 上午5:22, Tejun Heo 写道:
> Hello,
>
> This looks generally fine to me. Some nits below.
>
> > +static inline struct bio *throtl_qnode_bio_peek(struct throtl_qnode *qn)
> > +{
> > +	struct bio *bio1, *bio2;
> > +
> > +	/* qn for read ios */
> > +	if (qn->dispatch_sync_cnt == UINT_MAX)
> > +		return bio_list_peek(&qn->bios[SYNC]);
> > +
> > +	/* qn for write ios */
> > +	bio1 = bio_list_peek(&qn->bios[SYNC]);
> > +	bio2 = bio_list_peek(&qn->bios[ASYNC]);
> > +
> > +	if (bio1 && bio2) {
> > +		if (qn->dispatch_sync_cnt == THROTL_SYNC_FACTOR)
> > +			return bio2;
> > +		return bio1;
> > +	}
> > +
> > +	return bio1 ?: bio2;
> > +}
>
> Wouldn't it be simpler to write:
>
>          if (qn->dispatch_sync_count < THROTL_SYNC_FACTOR)
>                  return bio1 ?: bio2;
>          else
>                  return bio2 ?: bio1;
>
> > +/**
> > + * throtl_qnode_bio_pop: pop a bio from a qnode
> > + * @qn: the qnode to pop a bio from
> > + *
> > + * For read io qn, just pop bio from sync queu and return.
> > + * For write io qn, the target queue to pop was determined by the dispatch_sync_cnt.
> > + * Try to pop bio from target queue, fetch the bio and return when it is not empty.
> > + * If the target queue empty, pop bio from other queue instead.
> > + */
> > +static inline struct bio *throtl_qnode_bio_pop(struct throtl_qnode *qn)
> > +{
> > +	struct bio *bio;
> > +
> > +	/* qn for read ios */
> > +	if (qn->dispatch_sync_cnt == UINT_MAX)
> > +		return bio_list_pop(&qn->bios[SYNC]);
> > +
> > +	/* try to dispatch sync io */
> > +	if (qn->dispatch_sync_cnt < THROTL_SYNC_FACTOR) {
> > +		bio = bio_list_pop(&qn->bios[SYNC]);
> > +		if (bio) {
> > +			qn->dispatch_sync_cnt++;
> > +			return bio;
> > +		}
> > +		bio = bio_list_pop(&qn->bios[ASYNC]);
> > +		qn->dispatch_sync_cnt = 0;
> > +		return bio;
> > +	}
> > +
> > +	/* try to dispatch async io */
> > +	bio = bio_list_pop(&qn->bios[ASYNC]);
> > +	if (bio) {
> > +		qn->dispatch_sync_cnt = 0;
> > +		return bio;
> > +	}
> > +	bio = bio_list_pop(&qn->bios[SYNC]);
> > +
> > +	return bio;
> > +}
>
> This also seems like it can be simplified a bit.
>
> Thanks.

Indeed, I will make it more clear and send the v2.

Thanks.