linux-kernel - Re: [PATCH 2/2] zsmalloc: fine-grained inuse ratio based fullness grouping

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Message-ID: <CAJD7tka73PT8ka78rJBnd0JMtfjLY7SAr953MKNbZy5+icHD8g@mail.gmail.com>
Date:   Thu, 9 Feb 2023 22:04:23 -0800
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/2] zsmalloc: fine-grained inuse ratio based fullness grouping

On Thu, Feb 9, 2023 at 9:53 PM Sergey Senozhatsky
<senozhatsky@...omium.org> wrote:
>
> On (23/02/09 21:15), Yosry Ahmed wrote:
> > > We need to be able to do zs_stat_get(class, CLASS_USAGE_70) or
> > > zs_stat_get(class, CLASS_USAGE_10) in zs_stats_size_show() to
> > > show class's fullness stats.
> >
> > If we use #define FULLNESS_GROUPS 10 for example, we can break down
> > struct zs_size_stat from a single array to two arrays, one of the for
> > fullness groups and the other one for the rest of the stats (e.g.
> > OBJ_USED). We can have different helpers to update each, the former
> > taking in a fullness value (0 to FULLNESS_GROUPS-1), and the latter an
> > enum. WDYT?
>
> Wouldn't this be more code to review, maintain though? I mean,
> what do we gain with this - fewer values in enum?

I don't feel very strongly, but the patch above has a lot of hardcoded
values, multiple enums & static arrays. If we want to change the
number of fullness groups to 5 or 20, we modify all of them. Just
trying to make the code cleaner. If you think it will add a lot more
code to review/maintain, then maybe it's not worth it. I didn't really
give it a lot of thought.