From: Jan Kara <jack@suse.cz>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: Jan Kara <jack@suse.cz>, Michal Hocko <mhocko@suse.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Andrew Morton <akpm@linux-foundation.org>,
Linux MM <linux-mm@kvack.org>
Subject: Re: [PATCH] Revert "mm/page-writeback.c: print a warning if the vm dirtiness settings are illogical" (was: Re: [PATCH] mm: print a warning once the vm dirtiness settings is illogical)
Date: Tue, 28 Nov 2017 11:41:14 +0100 [thread overview]
Message-ID: <20171128104114.GL5977@quack2.suse.cz> (raw)
In-Reply-To: <CALOAHbBRiv48N_puVW18QX3MHoDU3CvMaa7BwxONAKWSOGWJcg@mail.gmail.com>
On Tue 28-11-17 18:33:02, Yafang Shao wrote:
> 2017-11-28 18:25 GMT+08:00 Jan Kara <jack@suse.cz>:
> > Hi Yafang,
> >
> > On Tue 28-11-17 11:11:40, Yafang Shao wrote:
> >> What about bellow change ?
> >> It makes the function domain_dirty_limits() more clear.
> >> And the result will have a higher precision.
> >
> > Frankly, I don't find this any better and you've just lost the additional
> > precision of ratios computed in the "if (gdtc)" branch the multiplication by
> > PAGE_SIZE got us.
> >
>
> What about bellow change? It won't be lost any more, becasue
> bytes and bg_bytes are both PAGE_SIZE aligned.
>
> - if (bytes)
> - ratio = min(DIV_ROUND_UP(bytes, global_avail),
> - PAGE_SIZE);
> - if (bg_bytes)
> - bg_ratio = min(DIV_ROUND_UP(bg_bytes, global_avail),
> - PAGE_SIZE);
> + if (bytes) {
> + pages = DIV_ROUND_UP(bytes, PAGE_SIZE);
> + ratio = DIV_ROUND_UP(pages * 100, global_avail);
> +
> + }
> +
> + if (bg_bytes) {
> + pages = DIV_ROUND_UP(bg_bytes, PAGE_SIZE);
> + bg_ratio = DIV_ROUND_UP(pages * 100, global_avail);
> + }
Not better... Look, in the original code the 'ratio' and 'bg_ratio'
variables contain a number between 0 and 1 as fractions of 1/PAGE_SIZE. In
your code you have in these variables fractions of 1/100. That's certainly
less precise no matter how you get to those numbers.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
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next prev parent reply other threads:[~2017-11-28 10:41 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-28 9:54 [PATCH] mm: print a warning once the vm dirtiness settings is illogical Yafang Shao
2017-11-25 16:05 ` Tetsuo Handa
2017-11-26 2:24 ` Yafang Shao
2017-11-26 2:42 ` Tetsuo Handa
2017-11-26 4:32 ` Yafang Shao
2017-11-26 8:03 ` Tetsuo Handa
2017-11-26 8:27 ` Yafang Shao
2017-11-26 8:46 ` Yafang Shao
2017-11-26 10:38 ` Tetsuo Handa
2017-11-27 8:06 ` Yafang Shao
2017-11-27 8:21 ` Michal Hocko
2017-11-27 8:29 ` Yafang Shao
2017-11-27 8:32 ` Yafang Shao
2017-11-27 8:37 ` Michal Hocko
2017-11-27 8:49 ` Yafang Shao
2017-11-27 8:52 ` Michal Hocko
2017-11-27 8:54 ` Yafang Shao
2017-11-27 9:04 ` Michal Hocko
2017-11-27 9:08 ` Yafang Shao
2017-11-27 8:34 ` Michal Hocko
2017-11-27 9:19 ` [PATCH] Revert "mm/page-writeback.c: print a warning if the vm dirtiness settings are illogical" (was: Re: [PATCH] mm: print a warning once the vm dirtiness settings is illogical) Michal Hocko
2017-11-28 3:11 ` Yafang Shao
2017-11-28 6:12 ` Yafang Shao
2017-11-28 7:45 ` Michal Hocko
2017-11-28 7:52 ` Yafang Shao
2017-11-28 9:43 ` Yafang Shao
2017-11-28 9:45 ` Michal Hocko
2017-11-28 10:09 ` Jan Kara
2017-11-28 10:16 ` Yafang Shao
2017-11-28 10:25 ` Jan Kara
2017-11-28 10:33 ` Yafang Shao
2017-11-28 10:41 ` Jan Kara [this message]
2017-11-28 10:44 ` Yafang Shao
2017-11-28 10:37 ` Jan Kara
2017-11-28 10:48 ` Michal Hocko
2017-11-28 11:05 ` Yafang Shao
2017-11-28 11:54 ` Michal Hocko
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