Re: [PATCH] null_blk: add "no_sched" module parameter

[weiping zhang]

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

Re: [PATCH] null_blk: add "no_sched" module parameter

[Jens Axboe]

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;

-- 
Jens Axboe