linux-kernel - Re: [GIT PULL] MM updates for 6.4-rc1

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Date:   Fri, 28 Apr 2023 09:17:44 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        mm-commits@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Lorenzo Stoakes <lstoakes@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [GIT PULL] MM updates for 6.4-rc1

On Fri, Apr 28, 2023 at 9:14 AM Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> On Fri, Apr 28, 2023 at 9:08 AM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > On Fri, Apr 28, 2023 at 9:03 AM Suren Baghdasaryan <surenb@...gle.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 they
> > > 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