| Message ID | 20241217024047.1091893-4-yukuai1@huaweicloud.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | lib/sbitmap: fix shallow_depth tag allocation | expand |
On 12/16/24 6:40 PM, Yu Kuai wrote: > From: Yu Kuai <yukuai3@huawei.com> > > The maximal default nr_requests is 256, and if disk can handle more than > 256 requests concurrently, use elevator in this case is useless, on the > one hand it limits the number of requests to 256, on the other hand, > it can't merge or sort IO because requests are dispatched to disk > immediately and the elevator is just empty. > > For example, for nvme megaraid with 512 queue_depth by default, we have > to change default elevator to none, otherwise deadline will lose a lot of > performance. > > Signed-off-by: Yu Kuai <yukuai3@huawei.com> > --- > block/elevator.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/block/elevator.c b/block/elevator.c > index 7c3ba80e5ff4..4cce1e7c47d5 100644 > --- a/block/elevator.c > +++ b/block/elevator.c > @@ -568,6 +568,17 @@ static struct elevator_type *elevator_get_default(struct request_queue *q) > !blk_mq_is_shared_tags(q->tag_set->flags)) > return NULL; > > + /* > + * If nr_queues will be less than disk ability, requests will be > + * dispatched to disk immediately, it's useless to use elevator. User > + * should set a bigger nr_requests or limit disk ability manually if > + * they really want to use elevator. > + */ > + if (q->queue_depth && q->queue_depth >= BLKDEV_DEFAULT_RQ * 2) > + return NULL; > + if (!q->queue_depth && q->tag_set->queue_depth >= BLKDEV_DEFAULT_RQ * 2) > + return NULL; > + > return elevator_find_get("mq-deadline"); > } Shouldn't this patch be submitted separately since it is independent of the rest of the patches in this series? Thanks, Bart.
Hi, 在 2024/12/18 5:50, Bart Van Assche 写道: > On 12/16/24 6:40 PM, Yu Kuai wrote: >> From: Yu Kuai <yukuai3@huawei.com> >> >> The maximal default nr_requests is 256, and if disk can handle more than >> 256 requests concurrently, use elevator in this case is useless, on the >> one hand it limits the number of requests to 256, on the other hand, >> it can't merge or sort IO because requests are dispatched to disk >> immediately and the elevator is just empty. >> >> For example, for nvme megaraid with 512 queue_depth by default, we have >> to change default elevator to none, otherwise deadline will lose a lot of >> performance. >> >> Signed-off-by: Yu Kuai <yukuai3@huawei.com> >> --- >> block/elevator.c | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/block/elevator.c b/block/elevator.c >> index 7c3ba80e5ff4..4cce1e7c47d5 100644 >> --- a/block/elevator.c >> +++ b/block/elevator.c >> @@ -568,6 +568,17 @@ static struct elevator_type >> *elevator_get_default(struct request_queue *q) >> !blk_mq_is_shared_tags(q->tag_set->flags)) >> return NULL; >> + /* >> + * If nr_queues will be less than disk ability, requests will be >> + * dispatched to disk immediately, it's useless to use elevator. >> User >> + * should set a bigger nr_requests or limit disk ability manually if >> + * they really want to use elevator. >> + */ >> + if (q->queue_depth && q->queue_depth >= BLKDEV_DEFAULT_RQ * 2) >> + return NULL; >> + if (!q->queue_depth && q->tag_set->queue_depth >= >> BLKDEV_DEFAULT_RQ * 2) >> + return NULL; >> + >> return elevator_find_get("mq-deadline"); >> } > > Shouldn't this patch be submitted separately since it is independent of > the rest of the patches in this series? Yes, this patch was added to this set by mistake. My bad. :( I'm supposed to use the cleanup patch from v1 to replace this patch. Thanks, Kuai > > Thanks, > > Bart. > > > . >
diff --git a/block/elevator.c b/block/elevator.c index 7c3ba80e5ff4..4cce1e7c47d5 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -568,6 +568,17 @@ static struct elevator_type *elevator_get_default(struct request_queue *q) !blk_mq_is_shared_tags(q->tag_set->flags)) return NULL; + /* + * If nr_queues will be less than disk ability, requests will be + * dispatched to disk immediately, it's useless to use elevator. User + * should set a bigger nr_requests or limit disk ability manually if + * they really want to use elevator. + */ + if (q->queue_depth && q->queue_depth >= BLKDEV_DEFAULT_RQ * 2) + return NULL; + if (!q->queue_depth && q->tag_set->queue_depth >= BLKDEV_DEFAULT_RQ * 2) + return NULL; + return elevator_find_get("mq-deadline"); }