Re: [PATCH -next v6 3/3] block, bfq: do not idle if only one group is activated

[Paolo Valente]

> Il giorno 23 mag 2022, alle ore 15:18, Yu Kuai <yukuai3@xxxxxxxxxx> ha scritto:
> 
> Now that root group is counted into 'num_groups_with_busy_queues',
> 'num_groups_with_busy_queues > 0' is always true in
> bfq_asymmetric_scenario(). Thus change the condition to '> 1'.
> 
> On the other hand, this change can enable concurrent sync io if only
> one group is activated.

This is ok.  Yet, if the mistakes I found in the other two patches are
actual errors, I wonder how these changes made it to pass your tests.

Thanks,
Paolo

> 
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> ---
> block/bfq-iosched.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 609b4e894684..142e1ca4600f 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -812,7 +812,7 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq)
>  * much easier to maintain the needed state:
>  * 1) all active queues have the same weight,
>  * 2) all active queues belong to the same I/O-priority class,
> - * 3) there are no active groups.
> + * 3) there are one active group at most.
>  * In particular, the last condition is always true if hierarchical
>  * support or the cgroups interface are not enabled, thus no state
>  * needs to be maintained in this case.
> @@ -844,7 +844,7 @@ static bool bfq_asymmetric_scenario(struct bfq_data *bfqd,
> 
> 	return varied_queue_weights || multiple_classes_busy
> #ifdef CONFIG_BFQ_GROUP_IOSCHED
> -	       || bfqd->num_groups_with_busy_queues > 0
> +	       || bfqd->num_groups_with_busy_queues > 1
> #endif
> 		;
> }
> -- 
> 2.31.1
>