Re: [PATCH 7/9] block/mq-deadline: Reserve 25% of tags for synchronous requests

[Bart Van Assche <bvanassche@acm.org>]

On 5/26/21 8:33 PM, Damien Le Moal wrote:
> On 2021/05/27 10:02, Bart Van Assche wrote:
>> For interactive workloads it is important that synchronous requests are
>> not delayed. Hence reserve 25% of tags for synchronous requests. This patch
> 
> s/tags/scheduler tags
> 
> to be clear that we are not talking about the device tags. Same in the patch
> title may be.

OK.

>> +static void dd_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
> 
> Similarly as you did in patch 1, may be add a comment about this operation and
> when it is called ?

Will do.

>> +static void dd_depth_updated(struct blk_mq_hw_ctx *hctx)
>> +{
>> +	struct request_queue *q = hctx->queue;
>> +	struct deadline_data *dd = q->elevator->elevator_data;
>> +	struct blk_mq_tags *tags = hctx->sched_tags;
>> +
>> +	dd->async_depth = 3 * q->nr_requests / 4;
> 
> I think that nr_requests is always at least 2, but it may be good to have a
> sanity check here that we do not end up with async_depth == 0, no ?

OK, I will add a check.

Thanks,

Bart.