linux-kernel - Re: [PATCH v11 0/6] mm / virtio: Provide support for unused page reporting

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Message-ID: <20191001144331-mutt-send-email-mst@kernel.org>
Date:   Tue, 1 Oct 2019 15:08:24 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Alexander Duyck <alexander.h.duyck@...ux.intel.com>
Cc:     David Hildenbrand <david@...hat.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        virtio-dev@...ts.oasis-open.org, kvm@...r.kernel.org,
        dave.hansen@...el.com, linux-kernel@...r.kernel.org,
        willy@...radead.org, mhocko@...nel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        vbabka@...e.cz, osalvador@...e.de, yang.zhang.wz@...il.com,
        pagupta@...hat.com, konrad.wilk@...cle.com, nitesh@...hat.com,
        riel@...riel.com, lcapitulino@...hat.com, wei.w.wang@...el.com,
        aarcange@...hat.com, pbonzini@...hat.com, dan.j.williams@...el.com
Subject: Re: [PATCH v11 0/6] mm / virtio: Provide support for unused page
 reporting

On Tue, Oct 01, 2019 at 09:21:46AM -0700, Alexander Duyck wrote:
> I thought what Michal was asking for was what was the benefit of using the
> boundary pointer. I added a bit up above and to the description for patch
> 3 as on a 32G VM it adds up to about a 18% difference without factoring in
> the page faulting and zeroing logic that occurs when we actually do the
> madvise.

Something maybe worth adding to the log:

one disadvantage of the tight integration with the mm core is
that only a single reporting device is supported.
It's not obvious that more than one is useful though.

-- 
MST