linux-kernel - Re: [PATCH 2/4] mm: thp: make deferred split shrinker memcg aware

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Date:   Wed, 12 Jun 2019 05:47:47 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     ktkhai@...tuozzo.com, kirill.shutemov@...ux.intel.com,
        hannes@...xchg.org, mhocko@...e.com, hughd@...gle.com,
        shakeelb@...gle.com, rientjes@...gle.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] mm: thp: make deferred split shrinker memcg aware

On Fri, Jun 07, 2019 at 02:07:37PM +0800, Yang Shi wrote:
> +	/*
> +	 * The THP may be not on LRU at this point, e.g. the old page of
> +	 * NUMA migration.  And PageTransHuge is not enough to distinguish
> +	 * with other compound page, e.g. skb, THP destructor is not used
> +	 * anymore and will be removed, so the compound order sounds like
> +	 * the only choice here.
> +	 */
> +	if (PageTransHuge(page) && compound_order(page) == HPAGE_PMD_ORDER) {

What happens if the page is the same order as THP is not THP? Why removing
of destructor is required?

-- 
 Kirill A. Shutemov