linux-kernel - Re: [PATCH] mm: migrate: make demotion knob depend on migration

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Message-ID: <875ytznjwk.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Fri, 15 Oct 2021 09:42:19 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Yang Shi <shy828301@...il.com>
Cc:     dave.hansen@...ux.intel.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: migrate: make demotion knob depend on migration

Yang Shi <shy828301@...il.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@...il.com>

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

Best Regards,
Huang, Ying