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

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Date: Fri, 26 Jan 2024 08:55:36 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Zhaoyang Huang <huangzhaoyang@...il.com>
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 03:59:48PM +0800, Zhaoyang Huang wrote:
> loop more mm and fs guys for more comments

I agree with everything Damien said.  But also ...

> > +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.

> > +       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?

> >  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

> >                 return IOPRIO_CLASS_INVALID << IOPRIO_CLASS_SHIFT;
> >
> >         return (prioclass << IOPRIO_CLASS_SHIFT) |
> >                 (priohint << IOPRIO_HINT_SHIFT) | priolevel;
> >  }
> > -

more gratuitous whitespace change