Re: [PATCH 8/8] block/bfq: use separate insertion lists

[Bart Van Assche <bvanassche@xxxxxxx>]

On 1/23/24 09:34, Jens Axboe wrote:
> Based on the similar patch for mq-deadline, this uses separate
> insertion lists so we can defer touching dd->lock until dispatch
                                           ^^^^^^^^
                                          bfqd->lock?
> with ~30% lock contention and 14.5% sys time, by applying the lessons
> learnt with scaling mq-deadline. Patch needs to be split, but it:

Is the last sentence above perhaps incomplete?

> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
> index 56ff69f22163..f44f5d4ec2f4 100644
> --- a/block/bfq-iosched.h
> +++ b/block/bfq-iosched.h
> @@ -516,10 +516,14 @@ enum {
>   struct bfq_data {
>   	struct {
>   		spinlock_t lock;
> +		spinlock_t insert_lock;
>   	} ____cacheline_aligned_in_smp;

Can lock contention be reduced further by applying ____cacheline_aligned_in_smp
to each spinlock instead of the surrounding struct?

Thanks,

Bart.