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Subject: Re: [PATCH] mm: vmscan: correct nr_reclaimed for THP
From:   William Kucharski <william.kucharski@oracle.com>
In-Reply-To: <87tve3j9jf.fsf@yhuang-dev.intel.com>
Date:   Thu, 9 May 2019 22:33:35 -0600
Cc:     Yang Shi <yang.shi@linux.alibaba.com>, hannes@cmpxchg.org,
        mhocko@suse.com, mgorman@techsingularity.net,
        kirill.shutemov@linux.intel.com, hughd@google.com,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
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References: <1557447392-61607-1-git-send-email-yang.shi@linux.alibaba.com>
 <87y33fjbvr.fsf@yhuang-dev.intel.com>
 <1fb73973-f409-1411-423b-c48895d3dde8@linux.alibaba.com>
 <87tve3j9jf.fsf@yhuang-dev.intel.com>
To:     "Huang, Ying" <ying.huang@intel.com>
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> On May 9, 2019, at 9:03 PM, Huang, Ying <ying.huang@intel.com> wrote:
> 
> Yang Shi <yang.shi@linux.alibaba.com> writes:
> 
>> On 5/9/19 7:12 PM, Huang, Ying wrote:
>>> 
>>> How about to change this to
>>> 
>>> 
>>>         nr_reclaimed += hpage_nr_pages(page);
>> 
>> Either is fine to me. Is this faster than "1 << compound_order(page)"?
> 
> I think the readability is a little better.  And this will become
> 
>        nr_reclaimed += 1
> 
> if CONFIG_TRANSPARENT_HUAGEPAGE is disabled.

I find this more legible and self documenting, and it avoids the bit shift
operation completely on the majority of systems where THP is not configured.