Re: [PATCH 4/6] blk-mq: use EWMA to estimate congestion threshold

Jens Axboe
2017-07-11T18:40:26Z

On 07/11/2017 12:21 PM, Ming Lei wrote:
> diff --git a/block/blk-mq.h b/block/blk-mq.h
> index 60b01c0309bc..c4516d2a2d2c 100644
> --- a/block/blk-mq.h
> +++ b/block/blk-mq.h
> @@ -133,4 +133,13 @@ static inline bool blk_mq_hw_queue_mapped(struct blk_mq_hw_ctx *hctx)
> return hctx->nr_ctx && hctx->tags;
> }
>
> +/* borrowed from bcache */
> +#define ewma_add(ewma, val, weight, factor) \
> +({ \
> + (ewma) *= (weight) - 1; \
> + (ewma) += (val) << factor; \
> + (ewma) /= (weight); \
> + (ewma) >> factor; \
> +})

Just put that in blk_mq_update_req_dispatch_busy(), or at least make it
a static function in blk-mq.c above that function. You don't use factor
at all.

--
Jens Axboe