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Date: Mon, 25 Apr 2016 06:30:01 -0700
Message-ID: <CAJu=L5-CjPWj4+Vi0QKPLvyCM32mBz_x_y_6fo-Q2gy_gE8OKA@mail.gmail.com>
Subject: Re: [PATCHv7 00/29] THP-enabled tmpfs/shmem using compound pages
From: Andres Lagar-Cavilla <andreslc@google.com>
To: Wincy Van <fanwenyi0529@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>, "Shi, Yang" <yang.shi@linaro.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Hugh Dickins <hughd@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dave Hansen <dave.hansen@intel.com>, Vlastimil Babka <vbabka@suse.cz>,
        Christoph Lameter <cl@gentwo.org>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Jerome Marchand <jmarchan@redhat.com>,
        Sasha Levin <sasha.levin@oracle.com>, Ning Qu <quning@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org
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On Sat, Apr 23, 2016 at 10:46 PM, Wincy Van <fanwenyi0529@gmail.com> wrote:
> On Wed, Apr 20, 2016 at 1:07 AM, Andres Lagar-Cavilla
> <andreslc@google.com> wrote:
>> Andrea, we provide the, ahem, adjustments to
>> transparent_hugepage_adjust. Rest assured we aggressively use mmu
>> notifiers with no further changes required.
>>
>> As in: zero changes have been required in the lifetime (years) of
>> kvm+huge tmpfs at Google, other than mod'ing
>> transparent_hugepage_adjust.
>
> 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.

Andres
>
> And huge tmpfs is a really good improvement for that.
>
>>
>> As noted by Paolo, the additions to transparent_hugepage_adjust could
>> be lifted outside of kvm (into shmem.c? maybe) for any consumer of
>> huge tmpfs with mmu notifiers.
>>
>
> Thanks,
> Wincy


-- 
Andres Lagar-Cavilla | Google Kernel Team | andreslc@google.com