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Date:   Wed, 7 Aug 2019 13:01:22 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Joel Fernandes <joel@joelfernandes.org>
Cc:     linux-kernel@vger.kernel.org,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
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        Kees Cook <keescook@chromium.org>, kernel-team@android.com,
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        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Will Deacon <will@kernel.org>,
        Brendan Gregg <brendan.d.gregg@gmail.com>
Subject: Re: [PATCH v4 1/5] mm/page_idle: Add per-pid idle page tracking
 using virtual indexing
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On Wed, 7 Aug 2019 06:00:13 -0400 Joel Fernandes <joel@joelfernandes.org> wrote:

> > > 8 files changed, 376 insertions(+), 45 deletions(-)
> > 
> > Quite a lot of new code unconditionally added to major architectures. 
> > Are we confident that everyone will want this feature?
> 
> I did not follow, could you clarify more? All of this diff stat is not to
> architecture code:


My point is that the patchset adds a lot of new code with no way in
which users can opt out.  Almost everyone gets a fatter kernel - how
many of those users will actually benefit from it?

If "not many" then shouldn't we be making it Kconfigurable?

Are there userspace tools which present this info to users or which
provide monitoring of some form?  Do major distros ship those tools? 
Do people use them?  etcetera.