linux-kernel - Re: [PATCH 3/7] dyndbg: select ZPOOL in Kconfig.debug

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Message-ID: <CAJfuBxzafMKtD88TmwYqQ-UuvS1Wvtn1ehz-7gtF8KtiRojFaw@mail.gmail.com>
Date:   Sun, 9 Aug 2020 09:09:46 -0600
From:   jim.cromie@...il.com
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Jason Baron <jbaron@...mai.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Changbin Du <changbin.du@...el.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [PATCH 3/7] dyndbg: select ZPOOL in Kconfig.debug

On Sat, Aug 8, 2020 at 11:06 PM Randy Dunlap <rdunlap@...radead.org> wrote:
>
> On 8/7/20 1:09 PM, Jim Cromie wrote:
> > dyndbg will next need zs_malloc and friends, so add config reqs now,
> > to avoid touching make-deps late in a patch-set.
> >
> > I used select in order not to hide dyndbg inadvertently.
> > I want to say recommends, since it could be an optional feature.
> > Whats the best way ?
>
> Hi Jim,
> Can you elaborate on what/why/when it could be an optional feature?
>

hi Randy,

I dont think making it optional adds any real value.
if ZPOOL/ZRAM/ZSWAP is not included, we dont get any of
that sweet sweet compression. or the off-lining of >1/2 the memory.
I've got 46 callsites enabled atm, which is more than average, ~3100
callsites offlined.
This is the payoff for the added complexity and memory (the site pointer)

fwiw, Im not entirely clear on which of ZPOOL/ZRAM/ZSWAP
is the correct dependency/ies.   ZSWAP feels like the best destination
for the data,
especially if the data can be pushed aggressively into it.