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

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