linux-kernel - Re: [PATCH] mm: vmscan: correct nr

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Date:   Thu, 9 May 2019 22:33:35 -0600
From:   William Kucharski <william.kucharski@...cle.com>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Yang Shi <yang.shi@...ux.alibaba.com>, hannes@...xchg.org,
        mhocko@...e.com, mgorman@...hsingularity.net,
        kirill.shutemov@...ux.intel.com, hughd@...gle.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: vmscan: correct nr_reclaimed for THP



> On May 9, 2019, at 9:03 PM, Huang, Ying <ying.huang@...el.com> wrote:
> 
> Yang Shi <yang.shi@...ux.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.