Re: [PATCH 3/3] block: introducing a bias over deadline's fifo_time

[Zhaoyang Huang]

On Fri, Feb 9, 2024 at 1:49 AM Jens Axboe <axboe@xxxxxxxxx> wrote:
>
> On 2/8/24 2:31 AM, zhaoyang.huang wrote:
> > diff --git a/block/mq-deadline.c b/block/mq-deadline.c
> > index f958e79277b8..43c08c3d6f18 100644
> > --- a/block/mq-deadline.c
> > +++ b/block/mq-deadline.c
> > @@ -15,6 +15,7 @@
> >  #include <linux/compiler.h>
> >  #include <linux/rbtree.h>
> >  #include <linux/sbitmap.h>
> > +#include "../kernel/sched/sched.h"
> >
> >  #include <trace/events/block.h>
> >
> > @@ -802,6 +803,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
> >       u8 ioprio_class = IOPRIO_PRIO_CLASS(ioprio);
> >       struct dd_per_prio *per_prio;
> >       enum dd_prio prio;
> > +     int fifo_expire;
> >
> >       lockdep_assert_held(&dd->lock);
> >
> > @@ -840,7 +842,9 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
> >               /*
> >                * set expire time and add to fifo list
> >                */
> > -             rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
> > +             fifo_expire = task_is_realtime(current) ? dd->fifo_expire[data_dir] :
> > +                     CFS_PROPORTION(current, dd->fifo_expire[data_dir]);
> > +             rq->fifo_time = jiffies + fifo_expire;
> >               insert_before = &per_prio->fifo_list[data_dir];
> >  #ifdef CONFIG_BLK_DEV_ZONED
> >               /*
>
> Hard pass on this blatant layering violation. Just like the priority
> changes, this utterly fails to understand how things are properly
> designed.
IMHO, I don't think this is a layering violation. bio_set_ioprio is
the one which introduces the scheduler thing into the block layer,
this commit just wants to do a little improvement based on that. This
commit helps CFS task save some IO time when preempted by RT heavily.

PS: [PATCHv9 1/1] block: introduce content activity based ioprio has
solved layering violation issue. Could you please have a look.
>
> --
> Jens Axboe
>