Re: [PATCH 1/2] mm/damon/core: modified and tunning damon_split_regions_of()

SeongJae Park
2026-01-16T03:18:43Z

On Thu, 15 Jan 2026 05:18:51 +0900 JaeJoon Jung <rgbi3307@gmail.com> wrote:

> On Thu, 15 Jan 2026 at 00:46, SeongJae Park <sj@kernel.org> wrote:
> >
> > Hello JaeJoon, thank you for continued interest in DAMON.
> >
> > On Tue, 13 Jan 2026 21:16:42 +0900 JaeJoon Jung <rgbi3307@gmail.com> wrote:
> >
> > > Before modification:
> > > sz_region
> > > |--------|--------|--------||--------|--------|--------|--------|
> > > nr_subs: 1 2 3 4 5 9
> > > split random: <----------- (*] randmon LOST -------------->
> > >
> > > When dividing sz_region at rand, the random value may be small, such as
> > > 1 or 2. At this time, there is a problem that only the front areas
> > > corresponding to 1 and 2 are divided, and the remaining back area
> > > becomes too wide. If the area is too wide, there will be many missed
> > > address access judgments.
> > >
> > > After modification:
> > > sz_region
> > > |--------|--------|--------|--------|--------|--------|--------||
> > > nr_subs: 1 2 3 4 5 9
> > > split from <------------ (sz_region / nr_subs) ------------------>
> > >
> > > It is recommended to divide sz_region evenly in the ratio (sz_region /
> > > nr_subs) rather than using rand. In this way, if you decide nr_subs well,
> > > you can logically match the number of divisions and their sizes.
> >
> > I was thinking about how to reply to this patch. Since it is taking unusually
> > long time, let me add short comments for direct future of this patch.
>
> After much thought, you ask a simple question below.
>
> >
> > The existing code uses random() for a reason. This change might break it. Can
> > you further explain what was the point of the use of random(), and why this
> > change is not breaking it?
>
> To find a needle in a haystack, is it right to keep poking around randomly?
>
> >
> > >
> > > Signed-off-by: JaeJoon Jung <rgbi3307@gmail.com>
> >
> > Unless you can give me a convincing answer to my above question,
> >
> > Nacked-by: SeongJae Park <sj@kernel.org>
> >
> > Same for your followup patch [1]. Btw, please send patches of same series as
> > one thread from next time.
>
> I sent you two after much deliberation so that you can see them clearly.

Unfortunately what I asked are still not clearly answered to me. And based on
our past conversations including the recent one that I acknowledged as a
communication failure [1] and this thread, I expect asking you more questions
will not work for me. I don't think that's someone's fault, but obviously
that's the current situation. I will not ask you more questions for the
reason, unless I get a reason to change my mind.

So, to make it crystal clear, for this patch and the one you posted together,

Nacked-by: SeongJae Park <sj@kernel.org>

Thanks,
SJ

[1] https://lore.kernel.org/20260101224420.73826-1-sj@kernel.org …