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Date:   Wed, 7 Aug 2019 16:45:30 -0400
From:   Joel Fernandes <joel@joelfernandes.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-kernel@vger.kernel.org,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
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        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>, Will Deacon <will@kernel.org>
Subject: Re: [PATCH v5 1/6] mm/page_idle: Add per-pid idle page tracking
 using virtual index
Message-ID: <20190807204530.GB90900@google.com>
References: <20190807171559.182301-1-joel@joelfernandes.org>
 <20190807130402.49c9ea8bf144d2f83bfeb353@linux-foundation.org>
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On Wed, Aug 07, 2019 at 01:04:02PM -0700, Andrew Morton wrote:
> On Wed,  7 Aug 2019 13:15:54 -0400 "Joel Fernandes (Google)" <joel@joelfernandes.org> wrote:
> 
> > In Android, we are using this for the heap profiler (heapprofd) which
> > profiles and pin points code paths which allocates and leaves memory
> > idle for long periods of time. This method solves the security issue
> > with userspace learning the PFN, and while at it is also shown to yield
> > better results than the pagemap lookup, the theory being that the window
> > where the address space can change is reduced by eliminating the
> > intermediate pagemap look up stage. In virtual address indexing, the
> > process's mmap_sem is held for the duration of the access.
> 
> So is heapprofd a developer-only thing?  Is heapprofd included in
> end-user android loads?  If not then, again, wouldn't it be better to
> make the feature Kconfigurable so that Android developers can enable it
> during development then disable it for production kernels?

Almost all of this code is already configurable with
CONFIG_IDLE_PAGE_TRACKING. If you disable it, then all of this code gets
disabled.

Or are you referring to something else that needs to be made configurable?

thanks,

 - Joel