linux-kernel - Re: [RFC PATCH] mm/damon: explain "effective quota" on kernel-doc comment

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Message-ID: <20241128095357.1530-1-honggyu.kim@sk.com>
Date: Thu, 28 Nov 2024 18:53:55 +0900
From: Honggyu Kim <honggyu.kim@...com>
To: SeongJae Park <sj@...nel.org>
Cc: damon@...ts.linux.dev,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Yunjeong Mun <yunjeong.mun@...com>,
	kernel_team@...ynix.com,
	Honggyu Kim <honggyu.kim@...com>
Subject: Re: [RFC PATCH] mm/damon: explain "effective quota" on kernel-doc comment

On Tue, 26 Nov 2024 11:43:47 -0800 SeongJae Park <sj@...nel.org> wrote:
> On Tue, 26 Nov 2024 17:24:33 +0900 Honggyu Kim <honggyu.kim@...com> wrote:
> 
> > Hi SeongJae,
> > 
> > Thanks very much for the quick response.
> 
> No problem, all owing to your kind report!
> 
> > I think it looks great but I
> > have some minor comments so please see my inline comments below.
> > 
> > Thanks,
> > Honggyu
> > 
> > On Mon, 25 Nov 2024 16:29:21 -0800 SeongJae Park <sj@...nel.org> wrote:
> > > The kernel-doc comment for 'struct damos_quota' describes how "effective
> > > quota" is calculated, but does not explain what it is.  Actually there
> > > was an input[1] about it.  Add the explanation on the comment.
> > > 
> > > [1] https://github.com/damonitor/damo/issues/17#issuecomment-2497525043
> > > 
> > > Cc: Yunjeong Mun <yunjeong.mun@...com>
> > > Cc: Honggyu Kim <honggyu.kim@...com>
> > > Signed-off-by: SeongJae Park <sj@...nel.org>
> > > ---
> > >  include/linux/damon.h | 10 +++++++---
> > >  1 file changed, 7 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/include/linux/damon.h b/include/linux/damon.h
> > > index a67f2c4940e9..a01bfe2ff616 100644
> > > --- a/include/linux/damon.h
> > > +++ b/include/linux/damon.h
> > > @@ -193,9 +193,13 @@ struct damos_quota_goal {
> > >   * size quota is set, DAMON tries to apply the action only up to &sz bytes
> > >   * within &reset_interval.
> > >   *
> > > - * Internally, the time quota is transformed to a size quota using estimated
> > > - * throughput of the scheme's action.  DAMON then compares it against &sz and
> > > - * uses smaller one as the effective quota.
> > > + * To convince the different types of quotas and goals, DAMON internally
> > > + * converts those into one single size quota called "effective quota".  DAMON
> > 
> > Could we use "effective size quota" instead of "effective quota"?
> > IMHO, it will better give an idea this is related to "esz" in the code,
> > which means effective size.
> 
> The above sentence is saying it as one single "size" quota, so calling it
> "effective size quota" here feels like unnecessary duplicates of the word
> ("size") to me.  I'd like to keep this sentence as is if you don't really mind.

Since the time or other goals are eventually transformed into a size
quota, I thought the "effective size quota" makes sense but I won't
stick to my term here.

We originally asked this question about the term "effective" itself as
we didn't find an explanation what "effective" means actually in the
doc.  It'd be better to have more explicit explanation as well.

> > 
> > > + * internally uses it as only one real quota.  The convert is made as follows.
> > 
> > (nit) "as only one" can be "as the only one".
> > (another nit) "The convert is made" can be "The conversion is made".
> 
> Nice eyes!  I will fix those.

Thanks, please do!

> > 
> > > + *
> > > + * The time quota is transformed to a size quota using estimated throughput of
> > > + * the scheme's action.  DAMON then compares it against &sz and uses smaller
> > > + * one as the effective quota.
> > >   *
> > >   * If @goals is not empt, DAMON calculates yet another size quota based on the
> > 
> > We better fix "empt" to "empty" together.
> 
> Nice catch!  I will fix so.

Ditto.

Thanks,
Honggyu

> > 
> > >   * goals using its internal feedback loop algorithm, for every @reset_interval.
> > > -- 
> > > 2.39.5
> > >
> 
> 
> Thanks,
> SJ