From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sat, 30 Sep 2017 09:40:56 +0800 From: weiping zhang To: Jens Axboe CC: Subject: Re: [PATCH] null_blk: add "no_sched" module parameter Message-ID: <20170930014052.GA23233@localhost.didichuxing.com> References: <20170929170951.GA18535@localhost.didichuxing.com> <04e29850-3634-131b-5098-85842873658e@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: <04e29850-3634-131b-5098-85842873658e@kernel.dk> Return-Path: zhangweiping@didichuxing.com List-ID: On Fri, Sep 29, 2017 at 11:39:03PM +0200, Jens Axboe wrote: > On 09/29/2017 07:09 PM, weiping zhang wrote: > > add an option that disable io scheduler for null block device. > > > > Signed-off-by: weiping zhang > > --- > > drivers/block/null_blk.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c > > index bd92286..3c63863 100644 > > --- a/drivers/block/null_blk.c > > +++ b/drivers/block/null_blk.c > > @@ -154,6 +154,10 @@ enum { > > NULL_Q_MQ = 2, > > }; > > > > +static int g_no_sched; > > +module_param_named(no_sched, g_no_sched, int, S_IRUGO); > > +MODULE_PARM_DESC(no_sched, "No io scheduler"); > > + > > static int g_submit_queues = 1; > > module_param_named(submit_queues, g_submit_queues, int, S_IRUGO); > > MODULE_PARM_DESC(submit_queues, "Number of submission queues"); > > @@ -1753,7 +1757,7 @@ static int null_init_tag_set(struct nullb *nullb, struct blk_mq_tag_set *set) > > g_hw_queue_depth; > > set->numa_node = nullb ? nullb->dev->home_node : g_home_node; > > set->cmd_size = sizeof(struct nullb_cmd); > > - set->flags = BLK_MQ_F_SHOULD_MERGE; > > + set->flags = g_no_sched ? BLK_MQ_F_NO_SCHED : BLK_MQ_F_SHOULD_MERGE; > > This should be: > > set->flags = BLK_MQ_F_SHOULD_MERGE; > if (g_no_sched) > set->flags |= BLK_MQ_F_NO_SCHED; > That's right, I go through these two flags, if no io scheduler, BLK_MQ_F_SHOULD_MERGE can make sw ctx merge happen. I will send V2. Thanks weiping