linux-kernel - Re: [PATCH 07/10] blk-mq: add optional request->alloc_time

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Message-ID: <20190829154338.GT2263813@devbig004.ftw2.facebook.com>
Date:   Thu, 29 Aug 2019 08:43:38 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     axboe@...nel.dk, newella@...com, clm@...com, josef@...icpanda.com,
        dennisz@...com, lizefan@...wei.com, hannes@...xchg.org,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        kernel-team@...com, cgroups@...r.kernel.org
Subject: Re: [PATCH 07/10] blk-mq: add optional request->alloc_time_ns

Hello,

On Thu, Aug 29, 2019 at 04:22:48PM +0800, Hillf Danton wrote:
> >  static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
> > -		unsigned int tag, unsigned int op)
> > +		unsigned int tag, unsigned int op, u64 alloc_time_ns)
> >  {
> >  	struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
> >  	struct request *rq = tags->static_rqs[tag];
> > @@ -325,6 +325,9 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
> >  	RB_CLEAR_NODE(&rq->rb_node);
> >  	rq->rq_disk = NULL;
> >  	rq->part = NULL;
> > +#ifdef CONFIG_BLK_RQ_ALLOC_TIME
> 
> Not only matches start_time, but everal hunks may collapse into one
> if checking alloc_time is lifted up.
> 
> 	if (blk_queue_rq_alloc_time(rq->q))
> 		rq->alloc_time_ns = ktime_get_ns();
> 	else
> 		rq->alloc_time_ns = 0;

Can you please elaborate?  Lifted up where?

Thanks.

-- 
tejun