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Subject: Re: [PATCHv7 00/29] THP-enabled tmpfs/shmem using compound pages
To: Jerome Marchand <jmarchan@redhat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Hugh Dickins <hughd@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>
References: <1460766240-84565-1-git-send-email-kirill.shutemov@linux.intel.com>
 <571565F0.9070203@linaro.org> <571641AC.1050801@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>, Vlastimil Babka <vbabka@suse.cz>,
        Christoph Lameter <cl@gentwo.org>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        Andres Lagar-Cavilla <andreslc@google.com>, Ning Qu <quning@gmail.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org
From: "Shi, Yang" <yang.shi@linaro.org>
Message-ID: <571658CB.9080205@linaro.org>
Date: Tue, 19 Apr 2016 09:11:55 -0700
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On 4/19/2016 7:33 AM, Jerome Marchand wrote:
> On 04/19/2016 12:55 AM, Shi, Yang wrote:
>> 2. I ran my THP test (generated a program with 4MB text section) on both
>> x86-64 and ARM64 with yours and Hugh's patches (linux-next tree), I got
>> the program execution time reduced by ~12% on x86-64, it looks very
>> impressive.
>>
>> But, on ARM64, there is just ~3% change, and sometimes huge tmpfs may
>> show even worse data than non-hugepage.
>>
>> Both yours and Hugh's patches has the same behavior.
>>
>> Any idea?
>
> Just a shot in the dark, but what page size do you use? If you use 4k
> pages, then hugepage size should be the same as on x86 and a similar

I do use 4K pages for both x86-64 and ARM64 in my testing.

Thanks,
Yang

> behavior could be expected. Otherwise, hugepages would be too big to be
> taken advantage of by your test program.
>
> Jerome
>