linux-kernel - Re: [PATCHv3 1/1] block: introduce content activity based ioprio

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Date: Fri, 26 Jan 2024 17:28:58 +0800
From: Zhaoyang Huang <huangzhaoyang@...il.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: "zhaoyang.huang" <zhaoyang.huang@...soc.com>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, linux-fsdevel@...r.kernel.org, 
	Andrew Morton <akpm@...ux-foundation.org>, Jens Axboe <axboe@...nel.dk>, Yu Zhao <yuzhao@...gle.com>, 
	Damien Le Moal <dlemoal@...nel.org>, Niklas Cassel <niklas.cassel@....com>, 
	"Martin K . Petersen" <martin.petersen@...cle.com>, Hannes Reinecke <hare@...e.de>, 
	Linus Walleij <linus.walleij@...aro.org>, linux-mm@...ck.org, linux-block@...r.kernel.org, 
	linux-kernel@...r.kernel.org, steve.kang@...soc.com
Subject: Re: [PATCHv3 1/1] block: introduce content activity based ioprio

On Fri, Jan 26, 2024 at 4:55 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Fri, Jan 26, 2024 at 03:59:48PM +0800, Zhaoyang Huang wrote:
> > loop more mm and fs guys for more comments
>
> I agree with everything Damien said.  But also ...
ok, I will find a way to solve this problem.
>
> > > +bool BIO_ADD_FOLIO(struct bio *bio, struct folio *folio, size_t len,
> > > +               size_t off)
>
> You don't add any users of these functions.  It's hard to assess whether
> this is the right API when there are no example users.
Actually, the code has been tested on ext4 and f2fs by patchv2 on a
v6.6 6GB android system where I get the test result posted on the
commit message. These APIs is to keep block layer clean and wrap
things up for fs.
>
> > > +       activity += (bio->bi_vcnt + 1 <= IOPRIO_NR_ACTIVITY &&
> > > +                       PageWorkingset(&folio->page)) ? 1 : 0;
>
> folio_test_workingset().
>
> > > +       return bio_add_page(bio, &folio->page, len, off) > 0;
>
> bio_add_folio().
>
> > > +int BIO_ADD_PAGE(struct bio *bio, struct page *page,
> > > +               unsigned int len, unsigned int offset)
> > > +{
> > > +       int class, level, hint, activity;
> > > +
> > > +       if (bio_add_page(bio, page, len, offset) > 0) {
> > > +               class = IOPRIO_PRIO_CLASS(bio->bi_ioprio);
> > > +               level = IOPRIO_PRIO_LEVEL(bio->bi_ioprio);
> > > +               hint = IOPRIO_PRIO_HINT(bio->bi_ioprio);
> > > +               activity = IOPRIO_PRIO_ACTIVITY(bio->bi_ioprio);
> > > +               activity += (bio->bi_vcnt <= IOPRIO_NR_ACTIVITY && PageWorkingset(page)) ? 1 : 0;
> > > +               bio->bi_ioprio = IOPRIO_PRIO_VALUE_ACTIVITY(class, level, hint, activity);
> > > +       }
>
> why are BIO_ADD_PAGE and BIO_ADD_FOLIO so very different from each
> other?
These two API just repeat the same thing that bio_add_page and
bio_add_folio do.
>
> > >  static __always_inline __u16 ioprio_value(int prioclass, int priolevel,
> > > -                                         int priohint)
> > > +               int priohint)
>
> why did you change this whitespace?
>
> > >  {
> > >         if (IOPRIO_BAD_VALUE(prioclass, IOPRIO_NR_CLASSES) ||
> > > -           IOPRIO_BAD_VALUE(priolevel, IOPRIO_NR_LEVELS) ||
> > > -           IOPRIO_BAD_VALUE(priohint, IOPRIO_NR_HINTS))
> > > +                       IOPRIO_BAD_VALUE(priolevel, IOPRIO_NR_LEVELS) ||
> > > +                       IOPRIO_BAD_VALUE(priohint, IOPRIO_NR_HINTS))
>
> ditto
These white spaces are trimmed by vim, I will change them back in next version.
>
> > >                 return IOPRIO_CLASS_INVALID << IOPRIO_CLASS_SHIFT;
> > >
> > >         return (prioclass << IOPRIO_CLASS_SHIFT) |
> > >                 (priohint << IOPRIO_HINT_SHIFT) | priolevel;
> > >  }
> > > -
>
> more gratuitous whitespace change
>