Subject: Re: [RFC 0/6] Module for tracking/accounting shared memory buffers
To: Ruchi Kandoi <kandoiruchi@google.com>, gregkh@linuxfoundation.org,
        arve@android.com, riandrews@android.com, sumit.semwal@linaro.org,
        arnd@arndb.de, labbott@redhat.com, viro@zeniv.linux.org.uk,
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        peterz@infradead.org, akpm@linux-foundation.org, keescook@chromium.org,
        mhocko@suse.com, oleg@redhat.com, john.stultz@linaro.org,
        mguzik@redhat.com, jdanis@google.com, adobriyan@gmail.com,
        ghackmann@google.com, kirill.shutemov@linux.intel.com, vbabka@suse.cz,
        dan.j.williams@intel.com, hannes@cmpxchg.org, iamjoonsoo.kim@lge.com,
        luto@kernel.org, tj@kernel.org, vdavydov.dev@gmail.com,
        ebiederm@xmission.com, linux-kernel@vger.kernel.org,
        devel@driverdev.osuosl.org, linux-media@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
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From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <57FE6FC6.70205@linux.intel.com>
Date: Wed, 12 Oct 2016 10:15:50 -0700
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On 10/11/2016 04:50 PM, Ruchi Kandoi wrote:
> Any process holding a reference to these buffers will keep the kernel from
> reclaiming its backing pages.  mm counters don't provide a complete picture of
> these allocations, since they only account for pages that are mapped into a
> process's address space.  This problem is especially bad for systems like
> Android that use dma-buf fds to share graphics and multimedia buffers between
> processes: these allocations are often large, have complex sharing patterns,
> and are rarely mapped into every process that holds a reference to them.

What do you end up _doing_ with all this new information that you have
here?  You know which processes have "pinned" these shared buffers, and
exported that information in /proc.  But, then what?