| Message ID | 20220514090522.1669270-8-yukuai3@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | multiple cleanup patches for bfq | expand |
On Sat 14-05-22 17:05:21, Yu Kuai wrote: > It will only be called from bfq_bfqq_handle_idle_busy_switch() in > specific code branch, there is no need to precaculate > 'bfqq_wants_to_preempt' each time bfq_bfqq_handle_idle_busy_switch() > is caleld. > > Signed-off-by: Yu Kuai <yukuai3@huawei.com> Please see below: > @@ -1816,14 +1807,6 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, > (bfqq->bic || RQ_BIC(rq)->stably_merged) && > (*interactive || soft_rt))); > > - /* > - * Using the last flag, update budget and check whether bfqq > - * may want to preempt the in-service queue. > - */ > - bfqq_wants_to_preempt = > - bfq_bfqq_update_budg_for_activation(bfqd, bfqq, > - arrived_in_time); > - > /* > * If bfqq happened to be activated in a burst, but has been > * idle for much more than an interactive queue, then we ... > @@ -1918,7 +1900,7 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, > * (2) this switch of bfqq to busy changes the scenario. > */ > if (bfqd->in_service_queue && > - ((bfqq_wants_to_preempt && > + ((bfq_bfqq_update_budg_for_activation(bfqd, bfqq) && > bfqq->wr_coeff >= bfqd->in_service_queue->wr_coeff) || > bfq_bfqq_higher_class_or_weight(bfqq, bfqd->in_service_queue) || > !bfq_better_to_idle(bfqd->in_service_queue)) && So these changes are actually wrong because bfq_bfqq_update_budg_for_activation() relies on bfq_bfqq_non_blocking_wait_rq() but bfq_add_bfqq_busy() clears that. And bfq_add_bfqq_busy() is called between the place where bfq_bfqq_update_budg_for_activation() was called previously and now so your patch breaks this logic. Honza
在 2022/05/19 19:18, Jan Kara 写道: > On Sat 14-05-22 17:05:21, Yu Kuai wrote: >> It will only be called from bfq_bfqq_handle_idle_busy_switch() in >> specific code branch, there is no need to precaculate >> 'bfqq_wants_to_preempt' each time bfq_bfqq_handle_idle_busy_switch() >> is caleld. >> >> Signed-off-by: Yu Kuai <yukuai3@huawei.com> > > Please see below: > >> @@ -1816,14 +1807,6 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, >> (bfqq->bic || RQ_BIC(rq)->stably_merged) && >> (*interactive || soft_rt))); >> >> - /* >> - * Using the last flag, update budget and check whether bfqq >> - * may want to preempt the in-service queue. >> - */ >> - bfqq_wants_to_preempt = >> - bfq_bfqq_update_budg_for_activation(bfqd, bfqq, >> - arrived_in_time); >> - >> /* >> * If bfqq happened to be activated in a burst, but has been >> * idle for much more than an interactive queue, then we > ... >> @@ -1918,7 +1900,7 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, >> * (2) this switch of bfqq to busy changes the scenario. >> */ >> if (bfqd->in_service_queue && >> - ((bfqq_wants_to_preempt && >> + ((bfq_bfqq_update_budg_for_activation(bfqd, bfqq) && >> bfqq->wr_coeff >= bfqd->in_service_queue->wr_coeff) || >> bfq_bfqq_higher_class_or_weight(bfqq, bfqd->in_service_queue) || >> !bfq_better_to_idle(bfqd->in_service_queue)) && > > So these changes are actually wrong because > bfq_bfqq_update_budg_for_activation() relies on > bfq_bfqq_non_blocking_wait_rq() but bfq_add_bfqq_busy() clears that. And > bfq_add_bfqq_busy() is called between the place where > bfq_bfqq_update_budg_for_activation() was called previously and now so your > patch breaks this logic. Hi, You are right, thanks for the explanation, I'll remove this patch and the next patch in next version. Kuai > > Honza >
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index e36a16684fb4..1e57d76c8dd3 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -1555,10 +1555,11 @@ static int bfq_min_budget(struct bfq_data *bfqd) * responsibility of handling the above case 2. */ static bool bfq_bfqq_update_budg_for_activation(struct bfq_data *bfqd, - struct bfq_queue *bfqq, - bool arrived_in_time) + struct bfq_queue *bfqq) { struct bfq_entity *entity = &bfqq->entity; + bool arrived_in_time = ktime_get_ns() <= bfqq->ttime.last_end_request + + bfqd->bfq_slice_idle * 3; /* * In the next compound condition, we check also whether there @@ -1567,7 +1568,7 @@ static bool bfq_bfqq_update_budg_for_activation(struct bfq_data *bfqd, * would be expired immediately after being selected for * service. This would only cause useless overhead. */ - if (bfq_bfqq_non_blocking_wait_rq(bfqq) && arrived_in_time && + if (arrived_in_time && bfq_bfqq_non_blocking_wait_rq(bfqq) && bfq_bfqq_budget_left(bfqq) > 0) { /* * We do not clear the flag non_blocking_wait_rq here, as @@ -1768,17 +1769,7 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, bool *interactive) { bool soft_rt, in_burst, wr_or_deserves_wr, - bfqq_wants_to_preempt, - idle_for_long_time = bfq_bfqq_idle_for_long_time(bfqd, bfqq), - /* - * See the comments on - * bfq_bfqq_update_budg_for_activation for - * details on the usage of the next variable. - */ - arrived_in_time = ktime_get_ns() <= - bfqq->ttime.last_end_request + - bfqd->bfq_slice_idle * 3; - + idle_for_long_time = bfq_bfqq_idle_for_long_time(bfqd, bfqq); /* * bfqq deserves to be weight-raised if: @@ -1816,14 +1807,6 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, (bfqq->bic || RQ_BIC(rq)->stably_merged) && (*interactive || soft_rt))); - /* - * Using the last flag, update budget and check whether bfqq - * may want to preempt the in-service queue. - */ - bfqq_wants_to_preempt = - bfq_bfqq_update_budg_for_activation(bfqd, bfqq, - arrived_in_time); - /* * If bfqq happened to be activated in a burst, but has been * idle for much more than an interactive queue, then we @@ -1879,8 +1862,7 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, * guarantees or throughput. As for guarantees, we care * explicitly about two cases. The first is that bfqq has to * recover a service hole, as explained in the comments on - * bfq_bfqq_update_budg_for_activation(), i.e., that - * bfqq_wants_to_preempt is true. However, if bfqq does not + * bfq_bfqq_update_budg_for_activation(). However, if bfqq does not * carry time-critical I/O, then bfqq's bandwidth is less * important than that of queues that carry time-critical I/O. * So, as a further constraint, we consider this case only if @@ -1918,7 +1900,7 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, * (2) this switch of bfqq to busy changes the scenario. */ if (bfqd->in_service_queue && - ((bfqq_wants_to_preempt && + ((bfq_bfqq_update_budg_for_activation(bfqd, bfqq) && bfqq->wr_coeff >= bfqd->in_service_queue->wr_coeff) || bfq_bfqq_higher_class_or_weight(bfqq, bfqd->in_service_queue) || !bfq_better_to_idle(bfqd->in_service_queue)) &&
It will only be called from bfq_bfqq_handle_idle_busy_switch() in specific code branch, there is no need to precaculate 'bfqq_wants_to_preempt' each time bfq_bfqq_handle_idle_busy_switch() is caleld. Signed-off-by: Yu Kuai <yukuai3@huawei.com> --- block/bfq-iosched.c | 32 +++++++------------------------- 1 file changed, 7 insertions(+), 25 deletions(-)