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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 27 Apr 2023 20:03:19 -0700
Message-ID: <CAHk-=wi5=LfeCMv5ZPAtzWhJyW=y1rVJFTRBfgcqzoUNk5NRDA@mail.gmail.com>
Subject: Re: [GIT PULL] MM updates for 6.4-rc1
To:     Andrew Morton <akpm@linux-foundation.org>,
        Suren Baghdasaryan <surenb@google.com>
Cc:     mm-commits@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Lorenzo Stoakes <lstoakes@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>
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On Thu, Apr 27, 2023 at 3:33=E2=80=AFPM Andrew Morton <akpm@linux-foundatio=
n.org> wrote:
>
> - Suren Baghdasaryan has improved mmap_lock scalability by switching to
>   per-VMA locking.

.. related to this, we have that new PER_VMA_LOCK_STATS config entry,
which is 'default y' and has basically no help test.

Please don't do that.

I don't think any of the VM debugging stuff should likely be 'default
y' in the first place, but if they are, they should most definitely
have a good *explanation* for why they should be on for a normal user.

                      Linus