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From:   "Huang, Ying" <ying.huang@intel.com>
To:     Yang Shi <shy828301@gmail.com>
Cc:     dave.hansen@linux.intel.com, akpm@linux-foundation.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: migrate: make demotion knob depend on migration
References: <20211015005559.246709-1-shy828301@gmail.com>
Date:   Fri, 15 Oct 2021 09:42:19 +0800
In-Reply-To: <20211015005559.246709-1-shy828301@gmail.com> (Yang Shi's message
        of "Thu, 14 Oct 2021 17:55:59 -0700")
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Yang Shi <shy828301@gmail.com> writes:

> The memory demotion needs to call migrate_pages() to do the jobs.  And
> it is controlled by a knob, however, the knob doesn't depend on
> CONFIG_MIGRATION.  The knob could be truned on even though MIGRATION is
> disabled, this will not cause any crash since migrate_pages() would just
> return -ENOSYS.  But it is definitely not optimal to go through demotion
> path then retry regular swap every time.
>
> And it doesn't make too much sense to have the knob visible to the users
> when !MIGRATION.  Move the related code from mempolicy.[h|c] to migrate.[h|c].

Sounds reasonable to me.  Thanks!

> Signed-off-by: Yang Shi <shy828301@gmail.com>

Acked-by: "Huang, Ying" <ying.huang@intel.com>

Best Regards,
Huang, Ying