Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230427153345.451d86681f9c6775ea579e5a@linux-foundation.org>
 <CAHk-=wi5=LfeCMv5ZPAtzWhJyW=y1rVJFTRBfgcqzoUNk5NRDA@mail.gmail.com>
 <CAJuCfpHZSEjG2nti5iWbPQjWgXcHZ95hFS2FKwaPC-sZPdSznw@mail.gmail.com>
 <CAHk-=wg0SyFDp_sdcEH-D+LNxuzL_dWA1vZEowUN16n_+yRHPQ@mail.gmail.com> <CAJuCfpHouhrEtomhPe2sf+p0oG4pGFKb3xidhOXP6BN-PydY-Q@mail.gmail.com>
In-Reply-To: <CAJuCfpHouhrEtomhPe2sf+p0oG4pGFKb3xidhOXP6BN-PydY-Q@mail.gmail.com>
From:   Suren Baghdasaryan <surenb@google.com>
Date:   Fri, 28 Apr 2023 09:17:44 -0700
Message-ID: <CAJuCfpGcnJiJyU78v1r548W3bZ2LyfaYpr5huKKG8-WaiRHFHA@mail.gmail.com>
Subject: Re: [GIT PULL] MM updates for 6.4-rc1
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        mm-commits@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Lorenzo Stoakes <lstoakes@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Fri, Apr 28, 2023 at 9:14=E2=80=AFAM Suren Baghdasaryan <surenb@google.c=
om> wrote:
>
> On Fri, Apr 28, 2023 at 9:08=E2=80=AFAM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > On Fri, Apr 28, 2023 at 9:03=E2=80=AFAM Suren Baghdasaryan <surenb@goog=
le.com> wrote:
> > >
> > > I wanted these stats enabled by default to be able to identify
> > > possible pathological cases and to also let users disable them if the=
y
> > > can't tolerate even a small overhead in the pagefault path. Should I
> > > document this reasoning for the config option?
> >
> > You should document what the stats actually count (at a high enough
> > level for a user to understand), and why anybody would want to keep
> > them on.
> >
> > Honestly, 99% of the time, these are things that *developers* think
> > they might want, but that nobody else will ever ever use.
> >
> > Really, ask yourself if a normal user would ever look at them?
> >
> > Now, ask yourself whether this might be something that a cloud
> > provider would want to look at to gather statistics.
> >
> > And if it's the latter case, then it should be "default n", because
> > the default should be for the people who DO NOT KNOW, AND DO NOT CARE.
> >
> > The cloud provider will be using a custom config anyway. The default
> > is irrelevant for that use. The use that *matters* is literally the
> > clueless end user who I bet will never look at these numbers, and will
> > never be asked for them.
>
> Ok, sounds like this should be 'default n'. I'll prepare a patch. Thanks!

Should I send a replacement patch for "mm: introduce per-VMA lock
statistics" or a followup patch fixing it?

>
> >
> >                Linus