linux-kernel - Re: [PATCHv7 00/29] THP-enabled tmpfs/shmem using compound pages

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Message-ID: <CACzj_yW6gqrEaZABQKkJTooULCu5TvhgtdYaP0qUW5Hd=jTZJQ@mail.gmail.com>
Date:	Tue, 26 Apr 2016 22:02:59 +0800
From:	Wincy Van <fanwenyi0529@...il.com>
To:	Andres Lagar-Cavilla <andreslc@...gle.com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	"Shi, Yang" <yang.shi@...aro.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Hansen <dave.hansen@...el.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...two.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Ning Qu <quning@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCHv7 00/29] THP-enabled tmpfs/shmem using compound pages

On Mon, Apr 25, 2016 at 9:30 PM, Andres Lagar-Cavilla
<andreslc@...gle.com> wrote:
>>
>> We are using kvm + tmpfs to do qemu live upgrading, how does google
>> use this memory model ?
>> I think our pupose to use tmpfs may be the same.
>
> Nothing our of the ordinary. Guest memory is an mmap of a tmpfs fd.
> Huge tmpfs gives us naturally a great guest performance boost.
> MAP_SHARED, and having guest memory persist any one given process, are
> what drives us to use tmpfs.
>

OK. We are also using mmap.

Besides google's kvm userspace(as I know it is not qemu), google have another
userspace tool need to access guest memory, so that google use tmpfs?

If so, what function does that another userspace do?

Thanks,
Wincy